EARLY DEVELOPMENT OF HYDRA. 27 



servations seriously opposing it. He described the growth of a 

 coelenterate egg as taking place by the fusion or blending of the 

 egg with its neighboring cells, and pointed out further, that 

 vacuoles do not form about the engulfed cells in the case of those 

 eggs described by the supporters of the theory, but only about 

 their persistent nuclei. He concluded, therefore, that the amoeba 

 likeness was a misconception. Ciamician ('79) had previously 

 described the enlargement of an egg by the coalescence of the 

 egg and the cells surrounding it. 



The present conception may perhaps best be indicated by 

 quoting from Wilson ('oo) ^ who states that the egg cell in coelen- 

 terates may move actively about in the neighboring cells like an 

 amoeba and " in such cases (hydroids) the egg may actively feed 

 upon the surrounding cells, taking them bodily into its substance, 

 or fusing with them and assimilating their substance with its own. 

 In such cases {Tiibiilaria, Hydi^d) the nuclei of the food cells 

 long persist in the egg cytoplasm forming the so-called 'pseudo- 

 cells ' but finally degenerate and are absorbed by the egg!' 



It does not seem necessary to assume any active amoeboid pro- 

 pensities on the part of the egg of Hydra to account for the proc- 

 esses concerned in its growth. That the egg in its early history 

 is entirely devoid of any similarities to an amceba is evident from 

 the account given above of its growth at that time. The coales- 

 cence of the primitive ova is surely not comparable to any 

 amoebic activity. Nor do the ova migrate from one part of the 

 body to another as in the case of certain hydroids. The growing 

 egg does not, at first, at any rate, feed upon the surrounding cells 

 after the manner of an amoeba engulfing food particles. That 

 the surrounding cells become a part of the egg is true, but the 

 process by which the union is accomplished is simply a coales- 

 cence of a group of cells to form a larger mass over which a 

 single nucleus comes in time to hold sovereignty. Possibly but 

 one nucleus is functional from the beginning of the process. 

 Possibly one cell is at all times the controlling factor in all of the 

 processes, but this is difificult to prove. 



Nor does it seem necessary to assume any active amoeboid 

 properties on the part of the egg in order to account for the fact 



1 " The Cell in Development and Inheritance," p. 150. 



