1911.] NATURAL SCIENCES OF PHILADELPHIA. 457 



OBSERVATIONS ON SARCOCYSTIS RILEYI (STILES). 

 BY HOWARD CRAWLEY. 



On March 22, 1911, there was received at the laboratory of the 

 Zoological Division of the Bureau of Animal Industry, Washington, 

 D. C, a piece of the breast of a Mallard duck, in which were Sar- 

 cosporidian cysts. A preparation of the spores of this parasite, made 

 for purposes of identification, showed it to be Sarcocystis rileyi (Stiles). 

 This form is by no means rare in Mallards, Shoveller ducks and domestic 

 ducks. The preparation, however, showed certain morphological 

 details in the so-called spores which do not appear to have been 

 described. In consequence, a number of preparations were made, 

 the study of which brought to light the facts set forth below, which 

 are believed to be of considerable interest and of some theoretical 

 importance. 



The duck from which the material was obtained had been shot 

 near the mouth of the Illinois River, probably very shortly before 

 March 20. The specimen was handed to one of the veterinary inspec- 

 tors of the Bureau of Animal Industry, at Chicago, and by him for- 

 warded to Washington. The meat had merely been sprinkled with 

 borax, and reached Washington in good condition. It was quite 

 liberally parasitized. The cysts were confined mainly to the more 

 superficial portions of the breast of the duck, a good many lying 

 immediately beneath the connective tissue covering the muscle. 



It is believed that the parasites were still alive, or, if not, had been 

 dead for so short a time that they had not suffered any degeneration. 

 Examined fresh, they presented a picture characteristic of living- 

 organisms. They fixed well, and gave good stained preparations. 

 On the other hand, attempts to stimulate them to display movement 

 failed. Mounts were kept for several hours in the incubator, and 

 brought at once under the microscope. Others were kept for a con- 

 siderable period over the dark field illumination, since this procedure 

 heats the preparation. But in no case were any of the spores 1 seen 

 to move. 



1 The propagative bodies found in the cysts of Sarcosporidia are' conven- 

 tionally designated spores, and hence that term is used here. It is much more 

 likely, however, that they are the homologues of the sporozoites of Gregarines, 

 Coccidia and Hremosporidia. 

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