i:25] STUDIES ON GREGARINES— WATSON 15 



guished with the eye. I have been able to procure them in this manner 

 from the Acrididae. 



Cross-sections of the host intestine reveal the fact that the sporonts 

 lie close to the epithelial walls and are not scattered through the food 

 masses. In the Myriapoda, they lie deeply seated between the lobes of 

 the intestine where they are not easily dislodgd. Thus the parasites are 

 in position to absorb the richly laden digestive juices just before the lat- 

 ter reach the villi, and are not in danger of being swept along to the ex- 

 terior by the peristaltic movements in the intestine. 



In the Acrididae sporonts and trophozoites are found in the pyloric 

 caeca as well as in the intestine. In the Myriapoda the sporonts are able 

 to bore through the walls of the intestine and have been found, though 

 rarely, in the coelom. One species of the genus Steinina was found in a 

 beetle in masses on the outside of the intestinal walls, projecting into the 

 coelom. 



At least one family, the Stenophoridae, is intercellular in develop- 

 ment and the trophozoites are embedded in the intestinal walls of the 

 host ; in the Gregarinidae, however, one end only of the trophozoite is 

 projected into the epithelial cell of the host. 



SEASONAL VARIATION WITHIN THE HOST 



Investigation of the seasonal variation of gregarines was confined to 

 the Acrididae and the Gryllidae, of the order Orthoptera. It extended 

 over a period of two years. Locusts were collected around Urbana from 

 early spring until about June 20, and were then very generally para- 

 sitized but the number of parasites per host was small, averaging from 

 one to ten. The nymphs of the Acrididae which hatch in the early spring 

 were not infected in April but showed a slight infection when examined 

 in June. 



In the fall, observations were again made at Urbana and disclosed 

 a considerable increase in parasitism. Nearly every locust examined was 

 heavily infected, fifty parasites being an approximate minimum. 



The same increase in the fall was found to be true of the gregarines 

 in crickets. About fifty adults were examined at Urbana in June and it 

 was found that only five or six were infected, and these with very few 

 parasites. In the fall of the^ same year practically every cricket exam- 

 ined revealed a heavy infection. 



Crickets were examined frequentlj^ throughout July and August of 

 two successive summers at the Biological Laboratory, Cold Spring Har- 

 bor, L. I. The parasitism here steadily increased from sparse to heavy 

 inside of two months. Conditions there were particularly favorable to 

 the rapid increase. The crickets were collected on the Sand Spit, a long 

 narrow peninsula separating the inner and outer harbors, and were taken 



