AUTONOMOUS THEORY OF GASTRULATIVE MOVEMENTS 4 



result, the gastrula emerges from the gastrulative process as a general mos£ 

 of self-differentiating entities or territories. (See Spemann, '38, p. 107.) 



It necessarily follows, therefore, that the production of specific areas 

 territories of cells, each having a tendency to differentiate into a specific stru 

 tare, and the axiation of these areas along the primitive axis of the embryo a 

 two of the main functions of the gastrulative process. In figure 205A-E, di 

 grams are presented relative to the chick embryo showing the results of e 

 periments made by Rawles ('36), Rudnick ('44), and others. (See Rudnic 

 '44.) These experiments were made to test the developmental potencies 

 various limited areas of the chick blastoderm. A considerable overlapping 

 territories is shown, which stems, probably, from the fact that transplant 

 pieces often show potencies which are not manifested in the intact embry 

 Therefore, these maps should be regarded not with finality but merely 

 suggesting certain developmental tendencies. 



H. Autonomous Theory of Gastrulative Movements 



Our knowledge concerning the dynamics of gastrulation in the Chorda 

 is based largely on the classical observations of cell movement made 1 

 Conklin ('05) in Styela, the same author ('32) in Amphioxus, Vogt ('2^ 

 in various Amphibia, Oppenheimer ('36) in Fundulus, Pasteels ('36, '37b) 

 trout and chick, Vandebroek ('36) in the shark, and Spratt ('46) in tl 

 chick. For detailed discussions, concerning the morphodynamics of the g£ 

 trulative period, reference may be made to the works published by Roi 

 (1895), Spemann ('38), Pasteels ('40), Waddington ('40), and Schechtm; 

 ('42). 



The theory popularly held, regarding the movements of the major pr 

 sumptive organ-forming areas of the late blastula, is that a strict autonon 

 is present among the various groups of cells concerned with the gastrulati 

 process. Spemann ('38) p. 107, describes this theory of autonomy as follow 



Each part has already previously had impressed upon it in some way or oth 

 direction and limitation of movement. The movements are regulated, not in 

 coarse mechanical manner, through pressure and pull of the single parts, but th 

 are ordered according to a definite plan. . . . After an exact patterned arran^ 

 ment, they take their course according to independent formative tendencies whi 

 originate in the parts themselves. 



There are some observations, on the other hand, which point to an inte 

 dependence of the various cell groups. For example, we have referred to t 

 observations of Waddington ('33) and Spratt ('46) which suggest that t 

 movements of the mesoderm in the bird embryo are dependent upon t 

 inductive influence of the entoderm. Similarly, Schechtman ('42) points o 

 that presumptive notochordal material does not have the power to invagin£ 



