242 RESEARCHES IN HEI.MINTHOLOGV AND PARASITOLOCxY . 



The body of the worms was most narrowed in advance, from pale 

 red to nearly colorless in the largest and deeper to blood red in the 

 smaller ones ; with the intestine shining through of variable pea 

 green to greenish-brown and dark brown in the latter, and with the 

 tortuous ovaries and testes milk white. Cephalic extremity lighter 

 colored, strongly tapering and with distinctly trilobate mouth. Tail 

 very short, conical, the length about equal the breadth at base. The 

 male of more slender proportions, with the caudal end incurved and 

 the tail more pointed, with a row on each side of ten preanal papillae, 

 one on each side of the anus and two rows of two on each side of the 

 tail. Spicules of the penis long, linear, curved and equal. Pharynx 

 long, cylindrical clavate ; rectum very short. 



Worms closely agreeing with those of the Python I have observed 

 from two of our common snakes, the Hog-nose Snake, Heterodon 

 platyrhiniis, and the other, from the accompanying description, sup- 

 posed to be the Milk-snake, Ophiholus friangjdus. A portion of the 

 stomach of the latter, preserved with the worms, shows them to have 

 the same habits as those of the Python ; partially occupying the 

 recesses of the tumefaction of the mucous membrane. 



[No. 99. See Bibliography.] 



ON THE ORGANIZATION OF THE GENUS GREGARINA OF DUFOUR— 

 CHARACTER OF THE GENUS.* 



1. Gregarina Juli Marginati. 



Gregarhia /arvata, Leidy. Proc. A. N. S., vol. iv, p. 232. 



2. Gregarina Juli Pusilli. — White, translucent, oval. Cephalic 

 sac hexahedral, with the sides rounded or forming a double cone 

 base to base, with the upper apex subacute or truncated in younger 

 individuals. Posterior sac robust, oval ; granular contents fine, 

 translucent ; interior corpuscle globular, transparent ; nucleus trans- 

 parent, without nucleolus. Whole length from the i- 1500th inch 

 to the i-275th inch. Breadth of largest the i-5ooth inch. Diame- 

 ter of head of largest i-r 500th inch. 



Habitaiio7i. — Intestine of Jiilns pitsilliis. 

 Movements. — Its movements are not frequent. 



3. Gregarina Polydesyni Virginiensis. — White, tran.slucent, cla- 

 vate or oval. Cephalic sac campanulate, globular, or prolate, or 

 oblate spheriod, surmounted by a papillary thickening of the in- 

 tegument ; interior granular mass very fine and translucent. Pos- 



* Transactions American Philosophical Society, 1851. 



