858 THE ANIMAL KINGDOM. 



attain a fair size, e. g. Monocystis magna of the Earthworn \ in. (5 mm.) ; 

 but the giant of the group is Porospora gigantea of the Lobster, which may 

 attain { in. The adult is sometimes quite inert, sometimes active, gliding 

 evenly along, but the mode in which locomotion is effected has not been 

 discovered. Changes of shapes have been observed, especially in the 

 young form ; they are apparently due to movements or local accumu- 

 lations of protoplasm, which may or may not cause movements. The sub- 

 class is divisible into two orders, the Monocystidea, in which the body is 

 simple, and the Polycystidea^ in which it is divided by two septa into three 

 segments, with the doubtful exception of Porospora and the certain one of 

 Gamocystis, which has two segments, one large, the other very minute in 

 size, corresponding probably to the two first segments of other forms. 

 The first segment is the epimerite ; it is the part from which the other 

 two segments bud out, and is in later stages an organ of fixation in the 

 cell-host It is either immersed in the protoplasm of the cell-host, or if 

 cup-shaped, as in Lophorhynchtis insignis, grasps the ends of a number of 

 intestinal epithelial cells. The second segment is the protomerite, the 

 third and by far the largest, the deuteromerite, in which the nucleus is 

 lodged. A Polycystid possessing all three segments is known as a 

 Cephalin or Cephalont. Sooner or later it loses the epimerite, more or 

 less completely, and is then known as a Sporadin or Sporont 1 . 



Klossia alone among Coccidiidae has a distinct cell-membrane. The 

 remaining Gregarinida have a delicate cuticula, which is often finely 

 striated in a longitudinal direction. The striae in Lophorhynchus insignis 

 are due to the cuticle consisting of delicate vertical lamellae set on edge 

 side by side. Delicate hair-like processes are present in Callyntrochlamys, 

 lobular processes in Conorhynchus 2 . The retinacular processes of the 

 epimerite, when present, are probably formed by the ectoplasm. The pro- 

 toplasm of the body, except in Coccidiidae^ is usually divisible into a clear 

 exoplasm and a granular fluid endoplasm or entocyte. The former is 

 best developed at the two extremities of the body and constitutes the 

 chief bulk of the epimerite ; an outer firmer layer, the sarcocyte, is very 

 commonly differentiated from it. In the Polycystidea it is frequently 

 traversed by fine fibrils, usually transverse, rarely reticular, homogeneous, 

 or in Porospora^ composed of granules apposed in linear series. To these 

 fibrils a muscular function was at one time assigned, and they were 

 supposed to constitute a special contractile layer or myocyte. But the 



1 Schneider entertains the idea apparently that the epimerite i the equivalent of a monocystid 

 Coccidiidan, the proto- and deutero-merite, the equivalent of its spores. See his Tablettes Zoolo- 

 giques, p. 113 et seqq. 



2 The species of Monocystis which inhabit the vesiculae seminales of the Earthworm live within 

 the spermatospores. When the latter give origin to spermatozoa the Gregarine appears to be 

 coated with cilia ; and the moult that was supposed to take place merely signifies the escape of the 

 parasite from the sperm-blastophore. 



