VITALITY 497 



incompletely fused and this is only temporary (Fig. 206). To this 

 phenomenon the term conjugation is given. A conjugating ciliate, 

 however, is physiologically different from a vegetative indi\'idual and 

 may be distinguished by the general designation gamont. These 

 considerations lead to the following classification: 



(a) ConJ2tgation.—Tem\:>OTaTy cell fusion of gamonts; permanent 

 nuclear fusion. 



(b) Cop«/fl^zt»n.— Permanent fusion of cell bodies and cell nuclei 

 of gametes. 



[ (fl) Similar macrogametes or 



A. Isogametes \ gamonts (hologametes) . 

 [ (h) Similar microgametes. 



Gametes \ 



f (a) Dissimilar microgametes. 



B. Anisogametes | (b) Macrogametes and microgam- 

 [ etes (oogametes). 



(a) Hologametes and ConjiKjanfs.— The nearest approach to 

 conjugation of the ciliates is to be found in the fertilization phe- 

 nomena (pseudo-conjugation) of the Sporozoa, particularly in the 

 Gregarinida. Here, two gamonts (gametocytes) come together 

 but do not fuse; after the formation of a common cyst each cell 

 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 ciliates. Here a microgametocyte and a 

 macrogamete become associated in conjugation and without the 

 formation of a cyst membrane. The former produces four or 

 more nuclei by division and one of these penetrates the macro- 

 gamete and fuses with its nucleus. One of the conjugants thus 

 resembles a ciliate while the other one, the microgametocyte, resem- 

 bles a gregarine in that it degenerates and disappears. In ciliates 

 there is a mutual formation of gametic nuclei, a mutual interchange, 

 and a mutual fertilization. Here both indi\iduals correspond to 

 the macrogamete of Adelea. 



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* (Fig. ISO, p. 425). On this hypothesis which has been 



* 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. 

 32 



