WEISMANN'S THEORY OF THE GERMPLASM 41 



the corollary by no means follows that mother- and 

 daughter-cells must appear identical from the 

 beginning. For the identity under consideration 

 belongs only to the substance that is the bearer of 

 specific characters, to the hereditary mass ; besides 

 that, a unicellular organism contains other sub- 

 stances, substances that change from time to time 

 during its life. Many unicellular organisms pass 

 through a regular series of developmental stages ; 

 the stages themselves being inherited, and follow- 

 ing each other as infallibly as in the case of 

 embryonic stages of higher animals. 



The following will serve as examples of this. 

 Podophrya gemmipara, an Acinetan, in the adult 

 condition is attached by a long stalk, while the 

 free end, at which is the mouth, is provided with 

 suctorial tentacles. It reproduces by giving rise to 

 many little buds, ciliated on the upper surface like 

 free-swimming, hypotrichous infusoria. These, in 

 appearance, are quite unlike the parent organism, 

 and, after a vagrant existence in the water for some 

 time, they attach themselves to a surface and pro- 

 duce a stalk, tentacles with suctorial pseudopodia, 

 and so for the first time attain the maternal form. 



Some Gregarines are large, jointed cells, divided 

 into two pieces, a protomerite and a deutomerite ; 

 they are clad with a cuticle, under which lies a layer 

 of muscular fibrils. After conjugation they encyst, 

 the nucleus divides, and they break up into 

 numerous peculiarly-shaped boat-like structures, 

 (pseudonavicellffi), which afterwards are set free as 

 small, sickle-shaped embryos. These exceedingly 



