Introductio7i to Animal Alorphology. 



65 



Fig. 5- 



are close together : one slender, shorter, and im- 

 movable ; the other, stouter and movable. The latter 

 becomes detached, and looks like a nematode, and the 

 rest of the body also elongates into a worm-like form. 

 (These pseudo-filarise have, perhaps, been taken for 

 nematodes by Bnich and Leydi'g.) Both these worms 

 dilate at one end, and narrow at the other ; their 

 movements slacken, a nucleus and nucleolus appear, 

 and an outer membrane forms : thus 

 they become perfect Gregarines. 



They are found in the intestines of 

 Invertebrates, chiefly Arthropods,rarely 

 in Vertebrates. Allied forms called 

 Psorospermia may be stages of un- 

 known Gregarines, and consist of 

 spindle or pear-shaped cells, often 

 tailed, with clear rounded bodies atA.Monocystisiumbrici. 



,1 . ,. . - - B. Pixinia rubecula. 



their smaller end, and a protoplasm c. Pseudonaviceiia of 



, . 1 . . , , Zygocystis sp. 



mass which sometimes is emitted as d. Amoebiform stage. 

 an amoebiform body. They occur abundantly in the 

 muscles, &c., of Fishes and other Vertebrates. 



Two families exist: — i. Monocystidea {Siei'n), with one 

 compartment and a central nucleus ; including Mono- 

 cystis, found in worms (Fig. 5, A), the valves of the 

 human heart, human kidney, pine-wood, beetles, Eunice, 

 Nemerteans, &c. 2. Dicystidea, having two compartments, 

 with a septal layer of ectosarc between, and the nucleus in 

 the posterior; including Stylorhynchus, with hooks round the 

 head, found in Calopteryx ; Didymophyes, with three parts, 

 head, fore, and hind body ; Actinocephalus, with spines 

 round the head ; Gregarina, with no hooks, found in Ephemera 

 Lobster, &c. ; Pixinia, with hooks and a head separate from 

 the front segment of the body (Fig. 5, B). 



Leuckart and Diesing have shown that gregariniform 

 bodies are developed from the eggs of Echinorhynchus 

 Proteus (Gregarina miliaria and diffluens). 



F 



