THE GREGARINES AND COCCIDIA 353 



Leger proceeds to divide the two sections further by the number of sporozoites 

 produced in the oocyst, but we venture to doubt if this is a method of classi- 

 fication which is natural. In the section Adeleidea, Leger includes the hsemo- 

 gregarines as a family, Hcemogregarinidce, characterized by producing one 

 octozoic spore ; but this is true only of two species, so far as is known at 

 present, and certainly not of many others (see p. 378, infra}. 



There remains for mention the family Aggregatidce, comprising certain 

 organisms, generally regarded as coccidia, parasitic upon Cephalopods of 

 various genera (Sepia, Eledone, Octopus, etc.). These parasites fall into 

 numerous species, of which Moroff (94) enumerates . twenty-one, but they 

 are comprised in a single genus which has gone through many vicissitudes of 

 nomenclature, having figured at different times under the names Benedenia, 

 Legeria, Legerina, and Eucoccidium ; but when it had, apparently, settled 

 down under the last of these names, it was discovered that the schizogony, 

 formerly supposed to be absent in this genus of parasites, occurs in a distinct 

 host namely, a crab where it had been seen by Frenzel and named by him 

 Aggregata ; this name stands, therefore, as the " correct " name of this genus 

 of parasites. 



Not less debatable than the name of these parasites is their systematic 

 position. While, up to a comparatively recent time, their schizogonous 

 phases in crabs had been regarded as those of coelomic gregarines, their 

 sporogonous cycle in Cephalopods was accepted as that of a coccidian. 

 Siedlecki (652) investigated the sexual phases, and found a type of sporogony 

 quite in accordance with that of coccidia namely, sporonts (gametocytes) 

 separated from one another, the male gametocyte producing a great number 

 of microgametes, one of which fertilized a macrogamete, with subsequent 

 division of the zygote to form a number of sporoblasts and spores. 



Recently, however, Moroff published a note in which he maintained that the 

 fertilization was of a type quite different from that described by Siedlecki. 

 He asserted that the macrogametocyte gave rise before ; not after, fertilization 

 to a number of sporoblasts, and that the sporoblasts in question were the true 

 macrogametes, each of which, after being fertilized, gave rise to a single 

 spore. In other words, Moroff described the fertilization as being of the 

 gregarine-type, and not that characteristic of coccidia. Consequently these 

 organisms have been classified by Fantham and by Leger and Duboscq (645) 

 amongst the schizogregarines. 



In his latest work, however, Moroff (94) acknowledges that the proofs of 

 the process of fertilization alleged by him are inadequate to establish the 

 point at issue, and that further investigations are necessary ; he is no longer 

 prepared to insist on the gregarine-nature of these organisms. Until, there- 

 fore, the question has been settled by fresh observations, the account of the 

 sporogony and sexual phases given by Siedlecki must stand. These parasites 

 may be regarded as a distinct family of the coccidia, the Aggregatidce, 

 characterized by an alternation of hosts corresponding to an alternation of 

 generations. The life -cycle in its general outline is as follows: The spores 

 are produced in the bodies of Cephalopods ; the dead bodies of the Cephalopods, 

 killed in various ways ( by porpoises, for example), are eaten by crabs, which 

 thus infect themselves ; the spores germinate in the intestine of the crab and 

 liberate the sporozoites, which traverse the wall of the intestine and come to 

 rest in the subepithelial connective-tissue layer. There the parasite grows 

 to a large size, forming a cyst which bulges into the body-cavity, and repro- 

 duces itself by schizogony, a process which has been studied exhaustively by 

 Leger and Duboscq (645). The final result is a vast number of merozoites. 

 If now the crab be eaten and digested by a Cephalopod, the merozoites resist 

 the digestive juices and establish themselves in their new host. 



The cycle in the Cephalopods has been studied by Moroff. The merozoites 

 grow into sporonts or gametocytes which are not sexually differentiated, but 

 when their growth is complete sexual differences are seen in the mode of 

 gamete-formation. Whatever the method of fertilization, a number of 

 sporoblasts are formed from which the spores arise j each spore has a tough 



23 



