219] STUDIES ON GREG ARINES— WATSON 9 



cessive days. A little safranin, erythrosin, or other stain may be added 

 to the mixture and will be taken up by the parasites. The colored solu- 

 tion can be removed from the slide as the glycerine applications are 

 made stronger. 



The study of totos should be supplemented as far as possible with 

 sections. In the instance of the small species not visible to the eye, sec- 

 tions afford the only means of studying the exact location in the host. 

 The whole alimentary tract is fixed and sectioned intact. Sections must 

 be cut very thin, about two micra for the smaller species. Ehrlich's 

 hematoxylin has been found the most satisfactory stain; it may be used 

 alone or counter-stained with either erythrosin or eosin. Sections reveal 

 the relation of the young parasite to the host cell, whether attached by an 

 epimerite or intercellular, the position of the free sporonts in relation to 

 the cell walls, and various points in structure of the sporonts. By means 

 of sections the position of the sporont can be determined, whether inside 

 or outside of the alimentary tract or its appendages. If the parasite is 

 able to bore through the walls of the intestine into the coelom, the actual 

 burrowing process is often depicted in a series of sections; Avhether the 

 pyloric caBeca are a seat of infection is also revealed in this manner. 



PREVIOUS WORK ON GREGARINES 



In 1903 Minchin adequately summarized the history of gregarines 

 from the time of Redi, who in 1708 recorded the discovery of what was 

 possibly a gregarine, through Dufour, who gave in 1828 the first authen- 

 tic account of these forms and named the genus which he found Grega- 

 rina, up to the beginning of the present century. 



Other historians of the gregarines have been Lankester, in 1863, 

 Butschli, in 1882, and Leger, in 1892. 



Like all groups of which little is known, much of the literature of 

 the gregarines is purely systematic in character. Since Minchin 's synop- 

 sis was written in 1903, as well as previously, work on the gregarines has 

 been chiefly systematic. Many new species, a dozen new genera, and a 

 very few new families have been named in the last decade. The suborder 

 Schizogregarinae (Minchin) has received considerable attention from 

 such workers as Leger and Duboscq, Fantham, Siedlecki, Dogeil, and 

 Brasil, and they have described many new species from Crustacea, tra- 

 cheate Arthropoda and Holothuroidea. A few new species have been de- 

 scribed among the Eugregarinae by European and South American work- 

 ers, and in the United States Crawley, Hall, and Ellis have contributed 

 considerable data concerning new species, all those in the last named 

 country being parasitic in tracheate Arthropoda. 



