580 THE POPULAR SCIENCE MONTHLY 



swarm of gametes found in other Gregarines. Here, also, the internal 

 or " nursed ' ; condition of the gametes is a new development or 

 adaptation. 



Similarly in Paramecium the three divisions of the micronucleus 

 may be interpreted as representing an ancestral brood of conjugating 

 gametes, only two of which are now functional, the one representing a 

 macrogamete or female form, the other a microgamete or male cell. 

 Unlike Ophryocystis, the Paramecium individual does not become a 

 nurse for the conjugating gametes, but remains, as before, the mechan- 

 ism for the performance of the various physiological activities and the 

 vehicle of the somatic and germ plasms. 



The widely accepted view, therefore, as first formulated by Weis- 

 mann and repeatedly stated in general works on biology, that Protozoa 

 differ from Metazoa in having no equivalent of the somatic cells and 

 therefore no somatic, or natural, death, must be abandoned. In the 

 vast majority of Protozoa there is a clearly defined equivalent of somatic 

 cells and an equivalent of natural death. The conditions in Para- 

 mecium and its allies are different from those of other protozoa, the 

 old individual does not die at conjugation but is completely reorganized 

 and built up of parts derived from the product of fertilization exactly 

 as in Metazoa. The protozoon is not a potential germ cell, but like the 

 metazoon is the carrier of the racial germ plasm which, in the great 

 majority of protozoa is differentiated from the somatic plasm. As the 

 germ cells of the metazoon become segregated into a germinal epi- 

 thelium, becoming functional at maturity, so the germ plasm of the 

 protozoon becomes segregated as chromidia or granules of a specific kind 

 of chromatin, in the cell and is likewise functional at maturity. 



