368 



GERMINAL ORGANIZATION INDUCTION PHENOMENA 



mostly uses proposals of ancient descriptive embryologists (Hatschek, Hubrecht, 

 Assheton, A. Brachet, DeLange), The corresponding terms acrogenesis, notogenesis, 

 deutogenesis, cormogenesis, ourogenesis may be suggested to designate the constitution 

 of induced structures. This terminology will be consistently followed in the 

 present work. 



acro- 

 merit 



£< 



deuto- 

 merit 



cormo- 



merit 



(trunk) 



ouro- 

 merit 

 (tail) 



deut- 



►encephalon 



(chord- •> " ) 



prosencephalon 



or 

 acrencephalon 



Fig. 39. General terminology utilizable for the description of induction phenomena. To 

 depict the appearance of a whole region, such as the acromerit, deutomerit, etc., correspond- 

 ing compound words using -genesis can be employed. Acrogenesis and notogenesis will be 



frequently used here. Orig. 



In order to enter this exploration, we should first consider the operations 

 performed on the neurula', where territories can be chosen with sufficient pre- 

 cision, and then discuss the earlier stages. To detect the inducing capacity of 

 the archenteron roof, Mangold (1933) carefully dissected parts of this roof from 

 the overlying ectoblast, and inserted these pieces into the blastocoele of young 

 gastrulae. In these favorable surroundings the grafts preserve their full vitality, 

 are pushed by the movements of gastrulation against the ventral ectoblast, and 

 induce significant structures in this fully receptive reactor, while they themselves 

 produce the same tissues as they would have in their normal situs. The only 

 inconvenience in this procedure is that the implant may be located too close to 

 the organs of the host and may be submitted to some influence exerted by these. 

 In the numerous experiments done by Mangold (1933, 1936), one result especially 



^ It might be useful to recall that in the neural plate the hind part of the neuro-epithelium 

 will form the posterior somites of the trunk and all those of the tail {cf. Bijtel, 1956, 1958). 

 This potency is even controlled by an induction exerted by the underlying chordomesoblast 

 (SpofTord, 1945, 1948). 



