90 



THE INVERTEBRATA 



Suborder EUGREGARINARIA 



Gregarinidea which have no schizogony. 



The adult trophozoite has a stout cuticle and the ectoplasm contains 

 myonemes, longitudinal or transverse, or both. Partitions of the 

 ectoplasm without myonemes may (Fig. 80 F) divide the body into 

 three segments — the epimerite or fixing organ, protomerite, and deuto- 

 merite, which latter contains the nucleus. When ripe the trophozoites 

 become gamonts, joining in syzygies of two which together form a 

 gamocyst and give rise to gametes (iso- or anisogametes according to 



Fig. 77. Stages in the life history of Ophryocystis mesnili, A, Agamont, on 

 the epithelium of a Malpighian tubule of the host. B, Syzygy. C, Formation 

 of a cyst (gamocyst) and multiplication of nuclei. D, Formation of gametes. 

 E, Zygote. F, Spore case with sporozoites, still enclosed in residual proto- 

 plasm of gamonts. gam. gamete ; nii. nuclei of agamont; nu.' gamete nucleus ; 

 nu." nuclei of enveloping (residual) protoplasm; spz. sporozoites; str. striated 

 border of epithelium of Malpighian tubule; zyg. zygote. 



species) by multiple fission in which residual protoplasm remains. 

 Syngamy takes place within the cyst between the gametes of one 

 parent and those of the other. The zygotes secrete small oocysts 

 (pseudonavicellae) of their own, and within these divide into several 

 sporozoites ("falciform young"). Passing out of the host these are 

 swallowed by another of the same species, within which their cysts 

 are digested and a new infection begins by the sporozoites invading 

 cells of the host. These they eventually outgrow, and lie in a cavity 

 of the host, either entirely free or attached by an epimerite. 



