48 THE EVOLUTION OF CONTINUITY 



It may be added that in the hsemamceba Individual's 

 development we have the exhibition in a Discontinuously 

 Multicellular Individual of the phenomenon known as 

 Alternation of Generations in its true sense. For before 

 the sexual elements can be reproduced there must be inter- 

 vening stages, " asexual," or containing only potentially the 

 temporarily lost plans of the originally combining gametes. 

 The alternation is that of the intermediate stages with the 

 terminal sexual forms. 



SPH-SIRELLA. 



Another example of Discontinuously Multicellular Indi- 

 vidual is Sphaerella, usually termed a " unicellular alga." 

 Its growth-cycle is fundamentally similar to that of the 

 haemamceba, but it is mentioned here for one point of special 

 interest. For one finds it stated that at times if the gametes 

 of Sphaerella fail to conjugate they may behave like zoogonidia 

 (spores) and originate motile vegetative cells. There is, 

 it is suggested, an error here. In normal conjugation there 

 is, as it were, a shattering of " plans," and an institution of 

 complete disequUibrium, and all subsequent growth is for 

 the restoration of what has been lost — gamete characters 

 or identity. It may well be that a gamete which has failed 

 to conjugate may lose its equilibrium of identity in a non- 

 specific manner — and the cases of the punctured unfertilised 

 ovum of the frog, and the chemically fertilised egg of the 

 sea-urchin are parallel cases in point — but if such a gamete 

 did give rise to vegetative growth it would not really be 

 comparable to a spore in its behaviour. It would start an 

 abnormal Individual cycle. The spore, on the other hand, 

 is always an intermediate cycle-stage and can only originate 

 a part of an Individual. This matter is referred to again at 

 the close of the chapter dealing with Parthenogenesis. 



