FASCIOLARIA. 



883 



mode b)- which the embryonic gut enclosure is \aV\\y^ i)lace, if 

 not the only mode. In their case neither senescence nor metab- 

 olism can be urged as the cause of the amitosis. Under ordi- 

 nary circumstances we should find the endoderm increasing by 

 mitosis, but here the mode of growth is very extraordinary, and 

 the case only finds explanation on the principle I have been 

 indicating. I do not know just what particular cause should be 

 assigned in the case of the endoderm, which is to be considered 

 as interfering with the mitosis ; perhaps it is the pressure condi- 

 tions existing in the enteron owing to the presence of such a 

 large amount of inert and foreign matter ; perhaps it is the 

 absence of the most favorable food for the endoderm, since the 

 food-ova have not yet begun to be consumed. 



Note. — Since revising the last proof of this article, the writer 

 has read with interest a i)assage in Dr. Uavis' article (Am. Xat. 

 38, p. 434) containing much the same idea vid.— - " It is possible 

 that direct division in the higher plants is in a sense a re\ersion 

 to early ancestral conditions, a reversion that comes on only wlitit 



