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 
were oriented in the most diverse ways in relation to one 
another.1°* 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.*°° 
If these double monsters,—and Roux has remarked 
10% 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. 591—595. Table XXXIV. 
260, 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. 276—284. Tables XI and XII. 
