Uber Induktion von Embryonalanlagen durch Implantation artfremder Organisatoren H Spemann und Hilde Mangold Sonderdruck Mikroskopische Anatomie Entwicklungsmechanik Herausgegeben Wilhelm Roux unter Mitwirkung von H Braus und H Spemann 100 Band 3 /4. Heft Julius Spring Facsimile reproduction of the cover of an original reprint of the 1924 article by Hans Spemann and Hilde Mangold, with a handwritten dedication by H. Spemann which reads"With best regards, HS ( Courtesy of K. Sander, Freiburg)
Facsimile reproduction of the cover of an original reprint of the 1924 article by Hans Spemann and Hilde Mangold, with a handwritten dedication by H. Spemann which reads "With best regards, H.S." (Courtesy of K. Sander, Freiburg)
The following article, reformatted and copy edited at the lDB Editorial Office with the help of Klaus ander, is Viktor Hamburgers translation of the original 1924 paper by Hans Spemann and Hilde Mangold entitled: Uber Induktion von Embryonalanlagen durch Implantation artfremder Organisatoren", published in Archiv fir Mikroskopische Anatomie und Entwicklungsmechanik, 638, 1924.This translation firstappeared in"Foundations of Experimental Embryology"(B H Willier ndJ. M. Oppenheimer, eds ) Prentice Hall, Inc, Englewood Cliffs, N.]. USA, Pp. 146-184, 1964.The Ilustrations were taken from the original article in german
The following article, reformatted and copy edited at the IJDB Editorial Office with the help of Klaus Sander, is Viktor Hamburger´s translation of the original 1924 paper by Hans Spemann and Hilde Mangold entitled: "Über Induktion von Embryonalanlagen durch Implantation artfremder Organisatoren", published in Archiv für Mikroskopische Anatomie und Entwicklungsmechanik, 100: 599- 638, 1924. This translation first appeared in "Foundations of Experimental Embryology" (B.H. Willier and J.M. Oppenheimer, eds.), Prentice Hall, Inc., Englewood Cliffs, N.J. USA, pp. 146-184, 1964. The illustrations were taken from the original article in German
Induction of Embryonic Primordia by implantation of Organizers from a Different species HANS SPEMANN and HildE MANGOLD (ee Praischoldt) Freiburg i.B. With 25 illustrations Submitted I June 1923) CONTENTS IL. Experimental Analys Experiment Triton 1921, Um 8b(Figs. 1-6); Triton 1922, Um 25b(Figs. 7-9); Thiton 1922, Um 214 him1922,Um131b(Fg1015;团hio1922,Um83(Fg.1618); Triton1922,Um132Fg.1925) II. Discussion of the results 1. Origin and prospective significance Inormal fate] of the organizer and site of its implantation 2. Behavior of the organizer after implantation 3. Structure of the secondary embryonic primordium 4. The causes for the origin of the secondary embryonic anlage 5. The organizer and the organizing center Ⅳ. Summary o V. References L. Introduction In a Triton embryo, at the beginning of gastrulation, the different areas are not equivalent with respect to their determination. It is possible to exchange by transplantation parts of the ectoderm at some distance above the blastopore thatin the course offurtherdevelopment would have become neural plate and parts that would have become epidermis, without disturbing normal development by this operation. This is feasible not only between embryos of the same age and of the same species but also tween embryos of somewhat different age and even between embryos of different species(Spemann 1918, 1921). For instance, presumptive epidermis of Thiton cristatustransplanted into the forebrain region of Triton taeniatuscan become brain; and presumptive brain of Triton taeniatustransplantec into the epidermal region of Thiton cristatus can become epidermis. Both pieces develop according to theirnewposition; howeverthey have thespecies characteristics with whichthey are endowed according to their origin. O. Mangold (1922, 1923) has extended these findings and has shown that prospective epidermis can furnish not only neural plate but even organs of mesodermal origin, such as somites and pronephric tubules. It follows from these experimental facts, on the one hand, that the exchangeable pieces are still relatively indifferent with respect to their future fate; and, on the other hand, that influences of some sort must prevail in the different regions of the embryo that determine the later fate of those pieces that are at first indifferent Notes added by the DB Editorial Office: 1. The serial number of each experiment, e.g. Um 25, refers to two embryos(a and ) between which transplants were exchanged. Thus"a"usually refers to the donor cristatus embryo while"b"typically e host embryo. 2. It is worthwhile noting that all figures in this paper were hand-drawn by Hilde Mangold. The drawings of histological sections are based on photographic paper prints. On these, each nucleus and cell border was traced with Indian ink. Thereafter, the silver halogenide grains were removed chemically, after which the drawing stood out on the white background. This method was described in Spemann(1918, P 545) [Abbreviations used in this paper: B blastopore; Oc, optic vesicles; pG, pericardium; pr. Med, primary neural tube; sec. Ch, secondary intestine; sec. Lab, secondary otocyst; sec. Med, secondary neural tube; sec. Mes, secondary mesoderm; s secondary pronephric duct; sec. Uu, secondary somite; Um X, Urmund(meaning"primitive d by the serial number"x"of the experiment
Induction of Embryonic Primordia by Implantation of Organizers from a Different Species by HANS SPEMANN and HILDE MANGOLD (Née Pröscholdt) Freiburg i.B. With 25 illustrations (Submitted 1 June 1923) CONTENTS I. Introduction II. Experimental Analysis Experiment Triton 1921, Um 8b (Figs. 1-6); Triton 1922, Um 25b (Figs. 7-9); Triton 1922, Um 214; Triton 1922, Um 131b (Figs. 10-15); Triton 1922, Um 83 (Figs. 16-18); Triton 1922, Um 132(Figs. 19-25). III. Discussion of the Results 1. Origin and prospective significance [normal fate] of the organizer and site of its implantation 2. Behavior of the organizer after implantation 3. Structure of the secondary embryonic primordium 4. The causes for the origin of the secondary embryonic anlage 5. The organizer and the organizing center IV. Summary of Results V. References I. Introduction In a Triton embryo, at the beginning of gastrulation, the different areas are not equivalent with respect to their determination. It is possible to exchange by transplantation parts of the ectoderm at some distance above the blastopore that in the course of further development would have become neural plate and parts that would have become epidermis, without disturbing normal development by this operation. This is feasible not only between embryos of the same age and of the same species but also between embryos of somewhat different age and even between embryos of different species (Spemann 1918, 1921). For instance, presumptive epidermis of Triton cristatus transplanted into the forebrain region of Triton taeniatus can become brain; and presumptive brain of Triton taeniatus transplanted into the epidermal region of Triton cristatus can become epidermis. Both pieces develop according to their new position; however they have the species characteristics with which they are endowed according to their origin. O. Mangold (1922, 1923) has extended these findings and has shown that prospective epidermis can furnish not only neural plate but even organs of mesodermal origin, such as somites and pronephric tubules. It follows from these experimental facts, on the one hand, that the exchangeable pieces are still relatively indifferent with respect to their future fate; and, on the other hand, that influences of some sort must prevail in the different regions of the embryo that determine the later fate of those pieces that are at first indifferent. Notes added by the IJDB Editorial Office: 1. The serial number of each experiment, e.g. Um 25, refers to two embryos (a and b), between which transplants were exchanged. Thus "a" usually refers to the donor cristatus embryo while "b" typically represents the host taeniatus embryo. 2. It is worthwhile noting that all figures in this paper were hand-drawn by Hilde Mangold. The drawings of histological sections are based on photographic paper prints. On these, each nucleus and cell border was traced with Indian ink. Thereafter, the silver halogenide grains were removed chemically, after which the drawing stood out on the white background. This method was described in Spemann (1918, p. 545). [Abbreviations used in this paper: Bl, blastopore; Oc, optic vesicles; pc, pericardium; pr. Med, primary neural tube; sec. Ch, secondary notochord; sec. D, secondary intestine; sec. Lab, secondary otocyst; sec. Med, secondary neural tube; sec. Mes, secondary mesoderm; sec. Pron, secondary pronephric duct; sec. Uw, secondary somite; Um X, Urmund (meaning "primitive mouth" or blastopore) followed by the serial number "X" of the experiment.]
16 Hans Spemann and Hilde Mangold A piece from the upper lip of the blastopore behaves quite differently. If it is transplanted into the egion that would later become epidermis, it develops according to its origin; in this region, a small secondaryembryonic primordium develops, withneural tube, notochord and somites(Spemann 1918) Such a piece therefore resists the determining influences that impinge on it from its new environment, influences that, forinstance, would readily make epidermis out of a piece of presumptive neural plate Therefore, it must already carry within itself the direction of its development; it must be determined. Lewis(1907) had already found this for a somewhat later developmental stage, when he implanted a small piece from the upper and lateral blastopore lip under the epidermis of a somewhat older embryo and saw it develop there into neural tissue and somites. It suggested itself from the beginning that effects might emanate from these already determined parts of the embryo that would determine the fate of the stillindifferent parts. This could be proved by cutting the embryo in half and shifting the halves with respect to each other; in this case, the determined part proved to be decisive for the direction that subsequent development would take. For instance, the animal half of the gastrula was rotated 90 or 180 with respect to the vegetal half; determination then spread from the lower vegetal piece that contained just the upper lip, to the upper animal piece Ortwo gastrula halves of the same side, for instance two right ones, were fused together. As a result, the half blastoporal lips completed themselves from adjacent material of the fused other half, and in this way, whole neural plates were formed (Spemann 1918) Thus, the concept of the organization centeremerged; that is, of a region of the embryo that has preceded the other parts in determination and thereupon emanates determination effects of a certain quantity in certain directions. The experiments to be presented here are the beginning of the analysis of the organization center. Such a more deeply penetrating analysis presupposes the possibility of subdividing the organization enter into separate parts and of testing their organizing capacities in an indifferent region of the embryo. This experiment has already been performed, and it was precisely this experiment that gave the firstindication that the partsofthe are notequivalentat the beginningofgastrulation(1918) owever, this intraspecific, homoplastic transplantation did not make it possible to ascertain how the secondary embryonic anlage that originated at the site of the transplant was constructed, that is, which part of it was derived from the material of the implant and which part had been induced by the implant from the material of the host embryo. The identification of these two components is made possible by heteroplastic transplantation, as for instance by implantation of organizers from Triton cristatusinto indifferent material of Triton taeniatus Thisexperiment, that followed logically fromitspresuppositions, wasperformed duringthesummers of 1921 and 1922 by Hilde mangold nee Proscholdt. It gave at once the expected result that has already beenreported briefly (Spemann 1921, pp 551 and 568). In the following, we shall present the basic fact in more detail I. Experimental Analysis Nothing new need be said concerning the experimental tech nique; it was the same as in previous experiments (Spemann Of the species of Tritonavailable, taeniatus can best tolerate the absence of the egg membrane, from early developmental stages on and it is the easiest torear. Hence the organizer that was to be tested for its capacities was always taken from a cristatu embryo and usually implanted into the presumptive epidermis of a taeniatusembryo. The place of excision was marked by implan tation of the piece removed from the taeniaius embryo; thatis, the Fig. 1. Um8crist. Thecristatus e t Experiment Triton 1921, Um 8b. The exchange was made the neurula stage. The taeniatus trans. between a cristatusembryo with distinctly U-shaped blastopore plantisdarkandelongated; itislocatedin and a taeniatusembryo of the same stage. A small circular piece at some distance above the blastopore was removed from the
16 Hans Spemann and Hilde Mangold A piece from the upper lip of the blastopore behaves quite differently. If it is transplanted into the region that would later become epidermis, it develops according to its origin; in this region, a small secondary embryonic primordium develops, with neural tube, notochord and somites (Spemann 1918). Such a piece therefore resists the determining influences that impinge on it from its new environment, influences that, for instance, would readily make epidermis out of a piece of presumptive neural plate. Therefore, it must already carry within itself the direction of its development; it must be determined. Lewis (1907) had already found this for a somewhat later developmental stage, when he implanted a small piece from the upper and lateral blastopore lip under the epidermis of a somewhat older embryo and saw it develop there into neural tissue and somites. It suggested itself from the beginning that effects might emanate from these already determined parts of the embryo that would determine the fate of the still indifferent parts. This could be proved by cutting the embryo in half and shifting the halves with respect to each other; in this case, the determined part proved to be decisive for the direction that subsequent development would take. For instance, the animal half of the gastrula was rotated 90° or 180° with respect to the vegetal half; determination then spread from the lower vegetal piece, that contained just the upper lip, to the upper animal piece. Or two gastrula halves of the same side, for instance two right ones, were fused together. As a result, the half blastoporal lips completed themselves from adjacent material of the fused other half, and in this way, whole neural plates were formed (Spemann 1918). Thus, the concept of the organization center emerged; that is, of a region of the embryo that has preceded the other parts in determination and thereupon emanates determination effects of a certain quantity in certain directions. The experiments to be presented here are the beginning of the analysis of the organization center. Such a more deeply penetrating analysis presupposes the possibility of subdividing the organization center into separate parts and of testing their organizing capacities in an indifferent region of the embryo. This experiment has already been performed, and it was precisely this experiment that gave the first indication that the parts of the embryo are not equivalent at the beginning of gastrulation (1918). However, this intraspecific, homoplastic transplantation did not make it possible to ascertain how the secondary embryonic anlage that originated at the site of the transplant was constructed, that is, which part of it was derived from the material of the implant and which part had been induced by the implant from the material of the host embryo. The identification of these two components is made possible by heteroplastic transplantation, as for instance by implantation of organizers from Triton cristatus into indifferent material of Triton taeniatus. This experiment, that followed logically from its presuppositions, was performed during the summers of 1921 and 1922 by Hilde Mangold née Pröscholdt. It gave at once the expected result that has already been reported briefly (Spemann 1921, pp. 551 and 568). In the following, we shall present the basic fact in more detail. II. Experimental Analysis Fig. 1. Um 8 crist.The cristatus embryo at the neurula stage. The taeniatus transplant is dark and elongated; it is located in the presumptive neural plate. 20X. Nothing new need be said concerning the experimental technique; it was the same as in previous experiments (Spemann, 1920). Of the species of Triton available, taeniatus can best tolerate the absence of the egg membrane, from early developmental stages on and it is the easiest to rear. Hence the organizer that was to be tested for its capacities was always taken from a cristatus embryo and usually implanted into the presumptive epidermis of a taeniatus embryo. The place of excision was marked by implantation of the piece removed from the taeniaius embryo; that is, the pieces were exchanged. Experiment Triton 1921, Um 8b. The exchange was made between a cristatus embryo with distinctly U-shaped blastopore and a taeniatus embryo of the same stage. A small circular piece at some distance above the blastopore was removed from the
Induction ofembryonic primordia by implantation oforganizers from a different species 17 cristatusembryo and replaced by a piece of presump- tive epidermis of the taeniatusembryo. This taeniatus implant was found, later on, as a marker in the neural plate of the cristatusneurula, between the right neural ld and the midline, and it extended to the blastopore slightly tapering toward the posterior end(Fig. 1).One livingembryo whether it co intotheinterior, and the sections, which are poorinthis region, did not show this either. The cristatusexplant (the"organizer")wasinserted on the right side of the taeniatus embryo, approxi- embryo at the meurula stage, with primary and sec. mately between the blastopore and the animal pole.It ondary neural plate the elongated white cristatus was found in the neurulastage tothe rightandventrally and drawn out in the shape of a narrow strip(Fig. 2). In its vicinity, at first a slight protrusion was observable; was still distinctly recognizable in the midline of this plate; it extended forward from the blaston plant a few hours later, neural folds appeared, indicating the contour of a future neural plate. The implant a long narrow strip, slightly curved, over about two-thirds of the plate(Fig 3) A This secondary neural plate, that developed in combination with the implanted piece, lagged only a tle behind the primary plate in its development. When the folds of the primary plate were partly closed, those of the secondary plate also came together. Approximately a day later, both neural tubes were closed. The secondary tube begins, together with the primary tube, at the normal blastopore and extends to the right of the primary tube, rostrad, to approximately the level where the optic vesicles of the latter would form. It is poorly developed at its posterior part, yet well enough that the cristatus implant was invisible from the outside. The embryo was fixed at this stage and sectioned as nearly perpendicularly to the axial organs as possible. The sections disclosed the following: The neural tube of the primary embryonic anlage is closed through the greater part of its length and detached from the epidermis, except at the anterior end where it is still continuous with it, and where its lumen opens to the exterior through a neuropore. The lateral walls are considerably thickened in front; this is perhaps the first indication of the future primary eye vesicles. The notochord is likewise completely detached, except at its posterior end where it is continuous with the unstructured cell mass of the tail blastema. In the mesoderm, four to five somites are separated from the lateral plates, as far as one can judge from cross sections of such an early stage Only the anterior part of the neural tube of the secondary embryonic anlage is closed and detached m ne at its largest cross-section: its walls are thick and its lumen is drawn out sideways(Fig. 4). Perhaps we cansee here the firstindication ofopticvesicles The central canal approaches thesurface atits posterior end and eventually opens to the outside. Then the neural plate rapidly tapers off; its hindmost portion is only a narrow ectodermal thickening(Figs. 5 and 6) Although the overwhelming mass of this secondary neural tube is formed by cells of the taeniatushost that can be recognized by the finely dispersed pigment, a long, narrow strip of completely unpigmented 液 ig. 4. Um 8b. Crass section through the anterior thirdof the embryo(cf Figs. 2 and 3)pr Med, primary neural tube;sec. Med, secondary neural tube. The implant (light) is in the mesoderm (sec. Mes. crist. ). 100r
Induction of embryonic primordia by implantation of organizers from a different species 17 a few hours later, neural folds appeared, indicating the contour of a future neural plate. The implant was still distinctly recognizable in the midline of this plate; it extended forward from the blastopore as a long narrow strip, slightly curved, over about two-thirds of the plate (Fig. 3). This secondary neural plate, that developed in combination with the implanted piece, lagged only a little behind the primary plate in its development. When the folds of the primary plate were partly closed, those of the secondary plate also came together. Approximately a day later, both neural tubes were closed. The secondary tube begins, together with the primary tube, at the normal blastopore and extends to the right of the primary tube, rostrad, to approximately the level where the optic vesicles of the latter would form. It is poorly developed at its posterior part, yet well enough that the cristatus implant was invisible from the outside. The embryo was fixed at this stage and sectioned as nearly perpendicularly to the axial organs as possible. The sections disclosed the following: The neural tube of the primary embryonic anlage is closed through the greater part of its length and detached from the epidermis, except at the anterior end where it is still continuous with it, and where its lumen opens to the exterior through a neuropore. The lateral walls are considerably thickened in front; this is perhaps the first indication of the future primary eye vesicles. The notochord is likewise completely detached, except at its posterior end where it is continuous with the unstructured cell mass of the tail blastema. In the mesoderm, four to five somites are separated from the lateral plates, as far as one can judge from cross sections of such an early stage. Only the anterior part of the neural tube of the secondary embryonic anlage is closed and detached from the epidermis. Here it is well developed; in fact, it is developed almost as far as the primary tube at its largest cross-section: its walls are thick and its lumen is drawn out sideways (Fig. 4). Perhaps we can see here the first indication of optic vesicles. The central canal approaches the surface at its posterior end and eventually opens to the outside. Then the neural plate rapidly tapers off; its hindmost portion is only a narrow ectodermal thickening (Figs. 5 and 6). Although the overwhelming mass of this secondary neural tube is formed by cells of the taeniatus host that can be recognized by the finely dispersed pigment, a long, narrow strip of completely unpigmented Figs. 2 (left) and 3 (right). Um 8b. The taeniatus embryo at the neurula stage, with primary and secondary neural plate; the elongated white cristatus implant is in the median plane of the latter. 20X. cristatus embryo and replaced by a piece of presumptive epidermis of the taeniatus embryo. This taeniatus implant was found, later on, as a marker in the neural plate of the cristatus neurula, between the right neural fold and the midline, and it extended to the blastopore, slightly tapering toward the posterior end (Fig. 1). One could not see in the living embryo whether it continued into the interior, and the sections, which are poor in this region, did not show this either. The cristatus explant (the “organizer”) was inserted on the right side of the taeniatus embryo, approximately between the blastopore and the animal pole. It was found in the neurula stage to the right and ventrally, and drawn out in the shape of a narrow strip (Fig. 2). ln its vicinity, at first a slight protrusion was observable; Fig. 4. Um 8b. Cross section through the anterior third of the embryo (cf. Figs. 2 and 3) pr. Med., primary neural tube; sec. Med., secondary neural tube. The implant (light) is in the mesoderm (sec. Mes. crist.). 100X