516 Mr. W. Nicoll on some 



on a different level from the rest and are smaller in size. 

 Thev measure '026 mm., while the others have a length of 

 •050-053 mm. 



The month opens in tlie oral sucker and is followed by a 

 narrow cesopliairus "50 mm. long. At a distance of '03 mm. 

 from the oral mucker there is a small muscular oesophageal 

 bulb (pharynx) measuring "10 X "05 mm. The oesophagus 

 divides into two intestinal diverticula just in front of the 

 ventral sucker. The diverticula extend the whole length of 

 the body. 



The testes, a pair of egg-shaped bodies, are situated in the 

 posterior third of the body, one behind the other, the posterior 

 being at a distance of "O-i mm. from the hinder end. They 

 measure '66 X ■40 mm. and •SOX'42 mm. respectively. 

 Further forward is the ovary, measuring '27 x '20 mm., the 

 long axis being transverse. The shell-gland lies behind the 

 ovary, two folds of the uterus intervening. The uterus is 

 much convoluted and the ova are numerous. The latter 

 vary in size and colour. Those nearest the ovary are largest. 

 They are colourless and measure '093 x "062 mm. Further 

 forward they assume a yellowish tint and their size is "087 x 

 "056 mm. The most anterior ova are brown in colour and 

 measure only "082 x 053 mm. 



The genital aperture is closely apposed to the anterior 

 border of the ventral sucker and lies slightly to the left of 

 the middle line. It is elliptical in outline. The vitelline 

 glands are lateral in position and extend from a distance of 

 "52 mm. behind the ventral sucker to the posterior extremity 

 of the body. They are dark in colour. 



The excietory system consists of a pair of narrow tubes, 

 one on each side, ruiming the whole length of the body. 

 'J hese give off numerous branches. At the posterior end 

 there is a large, distinct, excretory aperture, having the 

 appearance of being surrounded by a series of longitudinal 

 muscular fibres. 



A species of Echinosfomum {E. sj^hiulosurn) has already 

 been observed in Larus ridihundus. This is noted by 

 Diesing * and Bellingliam f- Echinosfomum spinulosum is 

 one of the commonest species of the genus and occurs in 

 Colymhus sf'pfetitrionah's, Podiceps crisiatus, Carlo graculus, 

 JS'umem'us arquatiis, Larus argentatus, capistratus, glaucus, 

 and som.e others. It has been described and figured by 



* Syst. Helm. i. p. 392. 



t Aui). & 3Jag. Isat. Hist. 1844, xiii. p. 426. 



