Double Formations 133 



plus reserve idioplasm) remains after division just as 

 it was before; in the second place, the conception by 

 which one makes the activation or non-activation of 

 the reserve idioplasm depend upon the abnormal or nor- 

 mal relations of the different nuclei with one another is 

 very similar to that of epigenesis with preformistic germs, 

 such as would correspond somewhat with the hypothesis 

 of DeVries or that of Oscar Hertwig. 



The formation of double monsters from a single 

 egg constitutes essentially an analogous case to that of 

 the formation of entire individuals from isolated blasto- 

 meres. We mention for example the experiments of 

 Wilson in which following the simple displacement in 

 relation to each other of the first two blastomeres of 

 the egg of Amphioxus, each of those blastomeres pro- 

 duced a gastrula united along a more or less extensive 

 surface with the gastrula produced by the other blasto- 

 mere in such a manner as to give rise to numerous and 

 very varied forms of double gastrulas in which the 

 axes and respective blastopores of the twin gastrulas 

 w r ere oriented in the most diverse ways in relation to one 

 another. 104 The same thing occurred in the similar 

 double monsters obtained by Oscar Schultze from frogs' 

 eggs, which were produced by compressing the egg be- 

 tween two horizontal plates and turning them over 

 immediately after the first segmentation. 105 



If these double monsters, and Roux has remarked 



104 E. B. Wilson: Amphioxus and the Mosaic-Theory of Devel- 

 opment. Journ. of Morphology, vol. VIII, No. 3. Boston, U. S. A., 

 Ginn. August 1893; P. 591595. Table XXXIV. 



106 O. Schultze: Die kiinstliche Erzeugung von Doppelbildungen 

 bei Froschlarven mit Hilfe abnormer Gravitationswirkung. Arch. f. 

 Entwicklungsmech. d. Organismen Bd. I. Heft 2. Leipzig, Engel- 

 mann, 1894. P. 276284. Tables XI and XII. 



