249 



tlie divisions gradnailj becomes subject to nioi-e variation, jet tlie 

 equatorial direction just as in former cleavages — though with a 



a'" b"2 



I 112 H'2I 



Fig. 12. Stage 32, animal 

 side. 



d'2' ^222 



Fig. 13. Stage 32 (the same 

 egg), vegetative side. 



deviation caused by the torsion — continues to predoininate. That 

 the torsion still proceeds is evident from fig. 15, which shows that 

 it is already more than 90°. 



At the beginning of this investigation 1 almost expected to find 

 that Volvox divides according to the spiral cleavage type. The figures 

 given by some investigators seemed to me to point in this direction. 

 No doubt tlds result would have been interesting with regard to the 

 derivation of the different cleavage types of Metazoa and their 

 mutual relation. A more direct relation between Volvox and the 

 lowest forms with a spiral cleavage type would not then appear 

 improbable, since, as shown above, there are other points of agreement. 

 That Volvox possesses chlorophyll would be no insuperable obstacle 



IcL' 



Fig. 14. Transition 32—64, 

 animal side. 



(a^ 



Fig. 15. Transition 32—64, 

 vegetative side. 



since it can hardly be doubted that animals must descend from 

 organisms with chlorophyll. No production of oi'ganic from inorganic 

 substance would have been possible otherwise. 



