526 On some new and little-known Trematodes. 



constricted again. They very nearly reach the extreme tip 

 ot the tail. 



The testes are large, irregularly-sliaped bodies, situated one 

 behind the other about '45 mm. from the posterior end of the 

 body. Their long axis is transverse and is included between 

 the gut-diverticula. The ovary lies just in front of the 

 anterior testis, is smaller than the latter and of somewhat 

 oval shape. The vitelline glands extend along each siile of 

 the body, ventral to the intestinal diverticula; they almost 

 reach the ventral sucker anteriorly, and are only a short 

 distance from the end of the tail posteriorly. The lobes are 

 fairly large and are particularly voluminous in some parts. 



The ova are not numerous (about 30), but are of con- 

 siderable size, -078 to -081 mm. X -040 to •042 mm. The 

 genital aperture is in front of the ventral sucker, but some- 

 what to the left side of the middle line, a feature characteristic 

 of the genus. 



At the extreme tip of the tail is the excretory aperture, to 

 which a long, narrow, straight tube runs down. At the top 

 of this tube there was in the living specimen a distinct 

 yellowish refractive body, oval in shape, measuring '014 x 

 •012 mm. After death this became less distinct and on 

 keeping some time it almost entirely disappeared. 



The only three species of this genus are all described by 

 Muhling *. P. redactum agrees with them in their 

 characteristic features, viz. (I) absence of oesophagus, 

 (2) position of testes and ovary, (3) disposition of vitelline 

 glands, (4) situation of genital aperture. It differs in habitat, 

 however, for the others are described from the intestine of 

 marine birds, Harelda glacialis and Fuligula nyroca [Nyroca 

 ferina) . 



In another three-spined stickleback a specimen (PI. XIII. 

 fig. 10) differing in many respects from the foregoing was 

 found. It presented the following features of difference : — 



Length 2*54 mm. ; breadth, comparatively uniform, '40- 

 •65 mm. Pharynx proportionately small. 



The testes are circular in outline and measure •28 mm. 

 and ^35 mm. in diameter respectively. The greatest differ- 

 ence occurs in the character and disposition of the vitelline 

 glands, which in this specimen extend in front of the ventral 

 sucker. The lobes also are smaller and much denser. 



Tiie ova are more numerous, but their size remains practi- 

 cally the same, viz. -075 to '081 mm. X '040 to -044 mm. The 



* Arcli. f. Naturg. Ixii. p. 243, and Ixiv. p. 96. 



