THE SPOROZOA 



In the Diplocystis found in the body -cavity of the cricket, 

 young trophozoites become associated in couples almost immedi- 

 ately after leaving the host-cell, and, according to Cue"not, no 

 solitary individuals are to be found above a certain size, since 

 all the old maids die off. In Diplocystis major the two associates 

 retain their distinctness, but in Diplocystis minor each couple 

 becomes surrounded by a common membrane (Fig. 22). In 

 CystoUa holothwiae early association has still more far-reaching 

 results, since a fusion, complete except as regards the nuclei, of 

 the two trophozoites takes place, so that the appearance of a 

 single Gregarine with two nuclei is produced, with no trace of 



FIG. 22. 



Precocious association in Diplocystis 

 minor, Cuen., of the cricket. TO, 

 common membrane uniting the two 

 associates ; g, grains of albuminoid re- 

 serve material. (After Cuenot, x about 

 120.) 



Fio. 23. 



Adult trophozoite of Cystobia holo- 

 thuriae (Ant. Schn.) (par. Holothuria 

 tubulosa), showing the two nuclei, 

 derived from the fusion of two indi- 

 viduals, but not separated by any 

 septum. (After Minchin.) 



any septum between them (Fig. 23). While in the cases 

 mentioned the association is undoubtedly a preliminary to the 

 conjugation of gametes, it is more difficult to interpret the 

 peculiar aggregations known as syzygies commonly seen in many 

 species, especially amongst Cephalina. Free Gregarine individuals 

 become attached to one another, the anterior extremity of one 

 adhering to the posterior end of the other (Fig. 24, a). Usually 

 such a syzygy consists of two individuals, but may be composed 

 of a chain of half-a-dozen or more (Fig. 24, c). The most anterior 

 individual is termed the primite, those behind it the satellites. The 

 latter are always individuals which have lost their epimerites, if 

 they belong to the Cephalina. The syzygy does not necessarily 

 take the form of a simple chain. Two satellites may be attached 

 side by side to the hinder end of the individual, primite or satellite, 

 in front of them (Fig. 24, b). In some cases the individuals com- 

 posing a syzygy are loosely attached and easily separated from 

 one another, and the members of it are not modified in any way. 

 In other cases the association is more intimate, and the satellite 



