VITALITY L>7:> 



proceeds to form a number of gametes which may be isogamous 

 or anisogamous. After the gametes are formed the gametocytes 

 degenerate and disappear while the gametes fuse two by two in 

 copulation. In the coccidian Adelea the phenomena are more 

 nearly like those of the filiates. Here a microgametocyte and a 

 macrogamete become associated in conjugation and without the 

 formation of a cyst membrane (gametocyst). The former produces 

 four or more microgametes by division and one of these penetrates 

 the macrogamete and fuses with its nucleus (Fig. 140). One of the 

 conjugants thus resembles a ciliate while the other one, the micro- 

 gametocyte, resembles a gregarine in that it degenerates and dis- 

 appears. In ciliates there is a mutual formation of gametic nuclei, 

 a mutual interchange and a mutual fertilization. Here both indi- 

 viduals correspond to the macrogamete of Adelina and fertilization 

 is mutual. 



B 



Fig. 140. — Adelina dimidiata A. Schn. .1, association of macrogametocyte and 

 smaller microgametocyte. B, nuclear divisions in microgametocyte and formation 

 of gametic nuclei. X 1400. (From Doflein after Shellack, Arbeit, aus d. kaiserlichen 

 Gesundheitsamt, courtesy of J. Springer.) 



It is possible that the peculiar conditions existing in present-day 

 ciliates may have resulted from conditions of pseudo-conjugation 

 as illustrated by the present-day gregarines, and that originally, 

 a group of gametes were formed which united to form zygotes 

 outside of the parent cells, or inside as in the case of Ophryocystis 

 mesnili 1 (Fig. 120, p. 281). On this hypothesis which has been 

 very generally accepted by protozoologists, the fusing nuclei of 

 conjugating ciliates are interpreted as the nuclei without cell bodies 



1 Some of the parasitic ciliates suggest the gregarines in their conjugation phe- 

 nomena. Thus in Balantidium coli, according to Brumpt (1909), two individuals 

 come together and form a common enveloping cyst membrane within which the 

 two cells now completely fuse. 



