76 PBACTICAL PARASITOLOGY 



Coccidium, and this in spite of its concentric stratification and 

 compact non-cellular structure. Similar errors have been made by 

 reporting the presence of Coccidia in the sweat - glands of swine 

 suffering from the so-called Schrotausschlag. 1 Errors such as these 

 show the necessity for caution, though where the details of technique 

 are faithfully carried out they are unlikely to arise. Schaudinn's work 

 on the Coccidia of Lithobius will be found a valuable aid to the study 

 of Coccidia in general. 2 



Order 2. Gregarinida. 



Gregarines occur exclusively in the invertebrates. They are 

 generally long, but may be oval, in shape. In their young stages 

 they are wholly or in part cell parasites, but the older forms live free 

 in the hollow organs (gut, body cavity). They are motile in both the 

 young and the adult stages. Unlike the Coccides, they possess a 

 cuticle, and there is a marked differentiation between the ecto- and 

 the endoplasm. Their life- history rarely (Schizogregarines) includes 

 an alternation of generation and never a change of host. The body 

 may be homogeneous (monocysts), or it may be separated, by means of 

 a membrane thrown out from the ectoplasm, into two divisions, which 

 are placed one behind the other (polycysts). The best subjects for 

 preliminary study are the monocysts of the seminal vesicles of the 

 earthworm, and the polycysts of the intestine of the mealworm. 



(a) Gregarines of the Earthworm. 



The mature cysts of Gregarines are nearly always present in the 

 seminal vesicles of large earthworms. Young cysts and the free 

 Gregarine forms occur with less regularity, though they generally 

 make their appearance in the spring and are rarely absent in about 

 the month of May. 



Earthworms are prepared as follows : The worm is stretched out 

 in a shallow dish with its darker dorsal aspect uppermost. The body- 

 tube is split at the anterior end with a sharp scalpel along the middle 

 line, and, after separating it from the intestinal canal by severing the 

 septa, it is turned back and pinned down. Three pairs of large 

 whitish-yellow bladders lying between the llth and 13th segments 

 will then become visible. These are the seminal vesicles. A small 

 portion should be cut off with the scissors and its contents diluted 

 with a normal saline previous to examination. 



1 M. Liihe, " Ueber den Schrotausschlag der Schweine und das sogenannte 

 'Coccidium fuscum,'" Centralbl. f. Bakt. u. Paraskde., part i, vol. xxix, 1901, 

 pp. 693-698. 



2 F. Schaudinu, " Zoolog. Jahrb.," Abt. f. Anat., vol. xiii, 1900, pp. 197. 



