18 Dr. W. Nicoll on the 



sucker, as in Goldschmidt's figure and my own. Botli Looss 

 and Odhner represent the diverticula as elongated sacs 

 arising from a point in front of the ventral sucker ; but in 

 reality they are short, oval, club-like structures, the 

 ajipearance of which is almost unique. Olsson's figure gives 

 an indication of this. 



The testes are two large globular bodies situated one on 

 each side of the ventral sucker at the level of its posterior 

 border. The ovary is situated further back near the ends of 

 the intestinal diverticula, median in position and of globular 

 or ovoid shape. The minute yolk-gland lies just in front of 

 the ovary and the fairly large receptacnlum serainis lies a 

 little behind atid to the right of the ovary. The genital 

 aperture is situated at the left margin of the body on the 

 level of the aperture of the ventral sucker. The cirrus- 

 pouch is moderately large, retort-shaped, and extends barely 

 beyond the posterior border of the ventral sucker. Its 

 ])03terior part lies dorsal to the outer portion of the sucker, 

 not, as Odhner and Goldschmidt represent it, entirely to the 

 lelt side of the sucker, except in compressed specimens. It 

 contains a bipartite vesicula seminalis, of which the posterior 

 part is considerably the larger, a small but distinct pars 

 prostatica, and a short ductus ejaculatorius, not lined by 

 spines. The uterus is confined mainly to the space behind 

 the ends of the intestinal diverticula and contains Miracidia 

 in all stages of development. A full description of these is 

 given by Looss and Goldschmidt. 



Looss's Zoogonus n^irus is in all probability identical with 

 Odhner''s Z. rubellus — at any rate, features sufficient to 

 distinguish them are not at present apparent. 



Derogenes various (Miiller). 



To the list of hosts in which I have already found this 

 species must be added Callionymus lyra (frequently in the 

 intestine), Trigla gurnardus (an immature specimen in the 

 stomach), Oadus callarias (occasionally in the stomach), and 

 Clupea sprattus (an immature specimen in the cajca). This 

 brings the number of British hosts of this species up to 15 

 and it is still to be found in many others. Although evi- 

 dently very widely distributed it very probably occurs most 

 frequently in Pleuronectidae and Gadidae. 



Lecilhoster gihhosus (Rud.). (PI. I. fig. 5.) 



= Derogenes cacozelus, mihi, Ann. & Mag. Nat. Hist. (7) xix. pp. 90-91, 

 pi. iii. tig. 10. 



This was e "^eously described as a new species from 



