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water current can easily be demonstrated by watching the little 

 particles suspended in (he water. If further we assume that by the 

 dexiotropic torsion during the cleavage the direction of the main axis 

 of (he cells undergoes a dexiotropic deviation and the flagella (hus 

 beat in the direction of (he arrows in fig. 16b, (hen the dexiotropic 

 rotation of the colony follows directly from (his assumpdon. Tha( 

 indeed the tlagella beat in this way needs no further proof, but 

 follows from the rotation itself. 



It would be intei-es(ing no doub( if a variety of Volrox globator 

 rotating to (he left, were discovered. It can haidly be expected 

 odierwise than (hat the cleavage here will equally l)elong to (he 

 inverse type. 



Have we accounted now for the rotating movement of Volvox 

 by (he torsion presenting itself during (he cleavage? In a causal 

 sense we have, if our suggestion is right. But how is the torsion of 

 (he cleavage cells to be accounted for? Phylogeneticaliy now I 

 should feel inclined to consider the torsion during the cleavage 

 rather as a consequence of the rotation of the adult animal than as 

 its cause. The study of ontogeny ever anew teaches us that we 

 mnst not consider the structure of the adult animal phylogeneticaliy 

 as a product of (he developmental processes, bnt we rather must account 

 for the latter by (he s(ructure of (he adult animal. Thus I would 

 see also in the torsion during the egg cleavage of Volvox nothing 

 bnt a very precociously appearing character of the adnlt form related 

 to the movement of the latter. This character, which- cannot be 

 demonstrated in the adult form, could be revealed only by the study 

 of its development. 



