60 Indications of a Central Zone of Development 



"However great," says Whitman quoting Gruber "the 

 difference between an infusorian and a highly organized 

 animal it cannot be a qualitative one. We can assume 

 that the same vital elements serve in both as the founda- 

 tion, only in ever new combinations. This kinship 

 declares itself very clearly in the correspondence of many 

 organs of the Infusoria with those of the higher or- 

 ganisms. We mention only the membranellae of the 

 Infusoria which are quite similar to the corner cells of 

 the mollusk Cyclas cornea." 34 



But we have already seen that when one cuts the 

 infusorian into several nucleated fragments the membra- 

 nellae can be formed from any given part of the proto- 

 plasm of the original individual, and can be arranged in 

 definite relation to one another under the influence of the 

 nucleus as a center from which the formative activity of 

 the entire organism radiates. It is then probable that the 

 formation and manner of disposition of the corner cells 

 of the mollusk Cyclas cornea may be due also to a similar 

 process of centroepigenetic nature. But this justifies us 

 in suspecting that in all pluricellular organisms whatso- 

 ever, every formative process commencing with normal 

 ontogeny is of centroepigenetic nature. 



This hypothesis is supported for example by the ex- 

 periments of King upon regeneration in Asteria vulgaris. 

 These have given among others the following results : 

 each of the arms cut off close to the body can remain liv- 

 ing by itself for two weeks but is incapable of regenerat- 



34 Whitman : The Inadequacy of the Cell-Theory of Development. 

 Biol. Lect. at the Mar. Biol. Lab. of Wood's Holl, Summer Session 

 1893; Boston U. S. A., Ginn, 1894. P. 118; and Journal of Morphol- 

 ogy, Boston U. S. A., August 1893. Vol. VIII, No. 3, P. 651 

 652; Fig. 2 and 3. 



