239] STUDIES ON GREGARINES WATSON 29 



always the less dense, being often nearly or quite transparent ; the 

 granular content is sparse and the large irregular granules are often 

 clustered near the septum, the rest of the space being filled with a color- 

 less fluid. The two parts differ in staining reactions also. The deuto- 

 merite contains fairly homogeneous endoplasm always densest at the 

 center of the mass, which is generally in the anterior third of the body. 

 In the posterior part of the attenuated forms, there is often so little en- 

 doplasm that the animal is transparent in the last fifth to third of its 

 body. The deutomerite is generally gray or black in its densest regions 

 and a lighter gray in regions of less density. 



The nucleus may be either spherical or ellipsoidal in the sporonts, 

 and varies considerably in relative size in different species. It generally 

 contains one karyosome in mature sporonts of this family, sometimes 

 more than one, but never many, and the karyosomes stain deeply, often 

 revealing the presence of one or two very small centrioles within. 



Longitudinal striations in the epicyte seem to be characteristic of 

 the family, and myonemes have been observed in a great many instances. 

 See figure 243 for these structures in Leidyana erratica, one of the 

 Gregarinidae. It is probable that both types of structures are invariably 

 present in motile gregarines and form the material foundation for pre- 

 vailing ideas as to the cause of motion. 



The epimerite seems to be an inconstant factor. Sometimes it is 

 well developed and even retained in specimens free in the lumen of the 

 intestine (Stenaphora nematoides, Fig. 15; 8. diplocorpa, and S. lacta- 

 ria). Generally, however, workers who have not sectioned the intestines 

 of hosts have failed to find any trace of an epimerite. This is possible 

 from the fact that development is intercellular and not extracellular as 

 in the Gregarinidae, in which family the epimerite alone penetrates the 

 cell. The whole trophozoite lies embedded and is able to obtain nourish- 

 ment by osmosis, just as it does when it becomes a sporont, taking food 

 in the former instance from the cell originally penetrated and those sur- 

 rounding rather than from the lumen. Often intercellular parasites are 

 found without epimerites (Leger and Duboscq, 1904, PI. XIV, Figs. 1, 

 3, 4) and yet in the same section there may be smaller specimens which 

 show the epimerite. The reason for the presence of an epimerite at all 

 is not evident unless it is an ancestral vestige, for it disappears while the 

 animal is still living an intercellular existence. 



The larger embedded trophozoites are found in various positions in 

 the host cells, generally, however, headed away from the lumen, i. e. 

 with their protomerites contiguous with the mesothelial lining of the in- 

 testine. Infrequently one is met which has the protomerite turned 

 toward the lumen (Leger and Duboscq, 1904, Fig. 6). Individuals of 

 Stenophora lactaria have frequently been found boring their way, pro- 



