THE NUCLEUS 



91 



Camptonema nutans, in which a pseud opodium arises directly from 

 each nucleus (Fig. 47).* In Acanthocystis (Fig. 18) an example 

 is seen of the second type, the evolution of which can be traced 

 in the actual development ; in the buds of Acanthocystis a centriole 

 is contained in the karyosome of the nucleus, but during the growth 



of the bud into the adult condition the centriole passes out of the 

 nucleus, and becomes the so-called "central grain" of the adult, 

 a corpuscle which occupies the centre of the body, and upon which 



* In Aclinosphcerium, however, there is no relationship between the pseud opodia 

 and the nuclei. From the researches of Hertwig (64), it is evident that in this 

 form the centrosomes are lost altogether during the vegetative life, and are formed 

 only in certain phases of the development (p. 115). 



