64 Iniroductwn to Animal ]\'lorphotogy. 



common stock of vacuolated protoplasm, with no skeleton 

 (CoUozoum), or a few needle-like, tangential spicules 

 (Sphserozoum). Raphidozoum has four-rayed, differentiated 

 spicules, znd. Collosphaeridse, each central capsule sup- 

 plied with a perforated sphere whose openings are simple 

 (Collosphasra) or tubular (Siphonosphasra). 



Class 7. Gregarinina. — Mostly parasitic, there- 

 fore degraded, forms,* one- or spuriously two-celled, f 

 with a distinct imperforate cuticle, on which may be 

 striae, knobs, ciliiform threads (Monocystis agilis), 

 hooks or spines. They have no pseudopodia, but the 

 ectosarc shows undulatory contractions from behind 

 forwards. There is always a nucleus, often fat 

 particles in the endosarc, but no contractile vesicle.^ 

 Sometimes there is a differentiated sub-cuticular layer 

 of transverse moniliform fibres (in G. gigantea of the 

 Lobster^). Food enters by endosmose or by invagina- 

 tion. Reproduction is by encystation, sometimes pre- 

 ceded by conjugation.il In the one-celled forms, the 

 body becomes globular, the nucleus vanishes, and the 

 contents form roundish, lanceolate bodies (pseudona- 

 vicellse), which become free, and each bursting emits 

 an active amoeboid plastide, which by degrees be- 

 comes developed into a Gregarine [Licberkuhn). In 

 G. gigantea, the amoeboid bodies are first gymno- 

 cytodes, which become quiescent and spheroidal ; then 

 a tail-like process projects, or sometimes two, which 



• A few free in decajdng timber {Huhner). 



t The cuticle does not dip in between the cells, but the septum consists 

 of ectosarc alone. 



X In Dicystidean forms, the nucleus is in one compartment alone, the 

 posterior. 



§ Lankester regards this as only thickened cuticle. 



II In G. longissima three have been found united. 



