OF DENISON UNIVERSITY. 59 



GENUS PTERODINA, Ehr. 



The lorica is flattened, round, or ovate in outline and flexible. Head funnel, 

 shaped, entirely withdrawn into the body when at rest, furnished with two lines of 

 cilia. Stomach sac-like with large cilia. The foot is ventral and consists of a 

 ringed basal portion and a short terminal joint which bears no claws. The intes- 

 tine is said to be continued through the tail having the anal opening at its end. 



The Pterodina is a good subject for use in obtaining a knowledge 

 of the rotifers as the viscera are quite distinct, the cross striation of the 

 muscles and the ciUated or beaker-cells of the lateral vessels being 

 particularly distinct. 



Pterodina patina, Ehr. 



{Plate I, Fig. III.) 



The form is circular with a slight emargination in front for the 

 withdrawal of the head. The head is funnel-shaped and bears a 

 double disc having good sized cilia. When extended, the eyes are 

 seen to occupy a position about one-third the width of the disc from its 

 sides. The pharynx is closely ciliated and leads into a comparatively 

 large maxtax in which a partial fusion of parts has taken place. The 

 stomach follows upon a very narrow oesophagus and is a curved sac 

 composed of large cells, each of which is filled with granular contents 

 and has fatty spheres within it. On either side the stomach is a strong 

 muscle passing from the sides of the head to the posterior third of the 

 body where it is fastened. When the head is withdrawn the muscles 

 are curved, but upon the protusion of the head become straight. On 

 either side the stomach is a large glandular mass composed of numer- 

 ous lobes made up of fused cells with large translucent flecks which 

 may be globules of the secretion. These glands open back of the 

 maxtax. While the stomach is curved to one side, the intestine lies 

 behind the tail and is curved upon itself, opening, as claimed by Eck- 

 stein, into a canal excavated in the tail. It is indeed certain that the 

 tail contains a canal and is ciliated at the distal extremity but we have 

 never been able to verify the statement referred to. The tail seems 

 to be more slender in our specimens than figured by European writers, 

 though it is exceedingly contractile. The contractile vessel seems to 

 be absent but two very distinct lateral canals are to be seen. The 

 breaker vessels are long and the cilia active. The ovary occupies one 

 side of the body, while the egg nearly fills the other when mature. 

 Large nuclei are discernible imbeded in a granular mass of yolk. The 



