540 BIOLOGY OF THE PROTOZOA 



to spread of the infection in the same host. Under the term " multi- 

 plicative reproduction" Doflein distinguishes this phase from the 

 reproduction following fertilization which he calls "propagative 

 reproduction." A relatively simple, but very interesting life cycle 

 is described by Leger in the case of Ophryocystis mesnili found in the 

 Malpighian tubules of the beetle Tenebrio molitor (Fig. 120, p. 231). 

 Here the asexual cycle is reduced to a process of equal division or 

 multiple division whereby a number of gamonts are formed. These 

 gamonts unite two by two in pseudo-conjugation. The nucleus of 

 each divides twice and one only of the resultant four nuclei becomes 

 the nucleus of a gamete. The two gametes become freed in a brood 

 chamber where they unite and in which the zygote gives rise to a 

 single sporoblast forming eight sporozoites. 



In Schizocystis sipunculi and in Eleutheroschizon dubosqui the 

 asexual cycle is represented by a process of multiple unequal divi- 

 sion, the agametes being formed by a process of internal budding 

 (Fig. 119, p. 230). 



In some cases, particularly in the cephalont gregarines, special- 

 ized sporoblast disseminating tubes known as sporoducts are formed 

 by the gametocysts. These are developed as ingrowths from the 

 cortical protoplasm which in the ripe gametocyst and under the 

 influence of moisture are evaginated as tubular processes through 

 which the sporocysts are emitted (Fig. 125, p. 240). In Gregarina 

 ovata they are quite short but reach a considerable length in other 

 species of Gregarina and in Clepsidrina. 



Gamete dimorphism is highly variable in different species of greg- 

 arines. Isogametes are produced by some species of Monocystis, 

 anisogametes by others although here the differences are slight. 

 Well-marked anisogamy is found in Pterocephalis nobilis (Duboscq 

 and Leger) and in Schaudinnella henleae (Xusbaum), but in gen- 

 eral differences in gametes are much less pronounced than in the 

 Coccidiomorpha (Fig. 215). 



The sporocysts in different species vary widely in form and in 

 sculpturing. The capsule is usually double, consisting of an inner 

 (endospore) and an outer (exospore) capsule, the latter sometimes 

 provided with short spines (Acanthospora) or long filaments (Cerato- 

 spora, Fig. 210). The typical number of sporozoites in a sporocyst 

 is eight, but this is not invariable. They are liberated by action of 

 gastric juices and emerge through preformed openings or by sepa- 

 ration of the two valves of the sporocyst. They creep out of the 

 endospore and make their way to epithelial cells within which the 

 first stages of their development occur. 



Order 1. Eugregarinida Doflein Emend. 



The great majority of known gregarines belong to this Order, the 

 agamous individuals living for long periods in the host before unit- 



