SPOROZOA, GREGARINIDA 407 



Genus Geneiorhynchus Schneider. Epimerite a tuft of short 

 bristles at end of neck; spores cyUndrical. 



G. aeschnae Crawley (Fig. 183, w). Sporadins 420/i long; cysts 

 and spores unknown; in Aeschna constricta. 



Family 13 Porosporidae Leger 



When naked or well-protected sporozoites enter the stomach 

 and midgut of a specific crustacean host, they develop into typi- 

 cal cephahne gregarines; 1, 2, or more sporadins become associa- 

 ted and encyst. Repeated nuclear and cytoplasmic division re- 

 sults in formation of an enormous number of gymnospores in 

 hindgut. Some observers consider this change as schizogony, and 

 hence include the family in the suborder Schizogregarinaria. 

 When the gymnospores are voided in the faeces of crustaceans 

 and come in contact with molluscan host, they enter, or are taken 

 in by phagocytosis of, the epithelial cells of the gills, mantle or 

 digestive system. These gymnospores are especially found in 

 abundance in the lacunae of the gills. Presently they become 

 paired and fuse (Hatt) ; the zygotes develop into naked or encap- 

 sulated sporozoites within the phagocytes of the molluscan host, 

 which when taken into a crustacean host, develop into cephaline 

 gregarines. 



Genus Porospora Schneider. Sporozoites formed in molluscan 

 phagocytes without protective envelope (Hatt). 



P. gigantea (van Beneden) (Fig. 184, a-f). Sporadins in Ho- 

 marus gammarus, up to 10 mm. long; cysts 3-4 mm. in diameter; 

 gymnospores spherical, 8)U in diameter (Hatt), containing some 

 1500 merozoites; in molluscan hosts, Mytilus minimus and Tro- 

 chocochlea mutahilis, develop into naked sporozoites {17 /jl long) 

 which are usually grouped within phagocytes. 



Genus Nematopsis Schneider. Development similar to that of 

 Porospora (Hatt); but each sporozoite in a double envelope. 



N. legeri (de Beau champ) {Porospora galloprovincialis Leger et 

 Duboscq) (Fig. 184, g-n). Hatt (1931) carried on a very careful 

 study of its development. Sporadins in a crustacean, Eriphia 

 spinifrons, in linear or bifurcated syzygy, 75-750jLi long; cysts 

 about 80iu in diameter; gymnospores 7m in diameter, composed of 

 fewer, but larger merozoites; permanent spores with a distinct 

 one-piece shell (endospore) and a less conspicuous epispore, about 

 14-15^ long and circular in cross-section, develop in numerous 



