208 



PEOTOZOA. 



the central mass. The structure of the body may be complicated by the pre- 

 sence of a partition wall which parts off the anterior end from the main mass 

 of the body. The anterior portion of the body gets in this way the appearance 

 of a head, upon which there may be formed here and there prominences in 

 the form of hooks and processes for the purpose of attachment. Nourishment 

 is effected by endosmosis, through the external walls. Motion is confined to 

 slow gliding forward of the feebly contractile body. 



In their full-grown state the Gregarina are frequently seen fastened to one 

 another, two or more together. This connected state precedes reproduction 

 (fig. 149). The two individuals lying with their long axes in the same straight 

 line contract and surround themselves with a common cyst, and after undergoing 



a process resembling segmentation, 

 divide into a number of small spore- 

 like balls, which become spindle- 

 shaped bodies (pseudonavicellse). 

 The cyst secreted round the conju- 

 gating individuals, or, as is often the 

 case, round a single individual, be- 

 comes a pseudonavicella cyst, and by 

 its bursting the spindle-shaped bodies 

 reach the exterior. The contents of 

 each Pseudonavicella sometimes gives 

 rise to a small amoeboid body, as may 

 be inferred from Lieberkiihn's obser- 

 vations on the Psorospcrnis of the 

 pike. In other cases (Monocystis, 

 Gonoxjiora, etc.) sickle-shaped bodies 

 arise in the spores, which, without 

 passing through an amoeboid stage, 

 give rise to young Gregarines. Mono- 

 cystis agilis from the testis of the 

 earth-worm. Greyarina L. Duf. 

 (Clcpsidrina Hammersch.) Body 

 with flat partition wall and wart-like 

 head at anterior end. In the young 

 stage the anterior end of Gr. llat- 

 taruni v. Sieb. is fixed in the cells of 

 the intestinal epithelium of Blatta. 

 Gr. polymorpliCL Hammersch. in the 

 meal- worm. 



[The Gregarines are found mainly 

 in Invertebrata. They may be divided 

 into two main groups, the Polycystidca and the Monocystldea. In the former, 

 which are found for the most part in Arthropods, there is a partition dividing 

 the body into two parts ; in the latter, which are found chiefly in Vermes, there 

 is no such partition.] 



The structures long known as Psorospcrms from the liver of the rabbit, the 

 slime of the intestine, the gills of fishes, and the muscles of many Mammalia, 

 etc., present a great resemblance to the Psei d jnavicellae ; but we are not yet 

 fully enlightened as to their nature. The cr.se is the same with the structures 

 known as Rainey'sor Mischer's corpuscles from the muscles of, e.g., the pig ; aud 



FIG. 150. Rainey'g corpuscles from the 

 flesh of a pig. a, An animal inside a mus- 

 cle fibre, b, Posterior end of the same, 

 strongly magnified ; C, cuticular layer ; 

 , spores. 



