74 Mr. W. Xicollo7j the 



apparatus, the vitelline glands, testes, and ova, all point to 

 its being a member of the genns Alloci'cadium. The ova are 

 excessively large and the ovary is absent, and on this aeeount 

 it is impossible to assign this form to any of the already 

 known memlKn-s of the genns, so that the dillicnlty of 

 proving the identity of Dist. simplex, Rnd., still remains. 



Olsson found this parasite oceurriug in Sebastes noi'veijicvs 

 (one or two fairly often), Gadus mtlanostumus (frequently 

 \\\xn\Qro\\^) , Rimiceps uiger (once, in great imml)crs), ^//^m/7/« 

 rulgar'is (a single specimen). Levinscn found it fairly often 

 in Coitus scorpius and Coitus gobiu {Phobetor ventralis) from 

 Greenland. Rudolphi's specimens were from the stomach of 

 Pleuronectes flesus. Odhner adds that he " has met with it 

 in a very considerable number of other Scandinavian marine 

 fishes from the west coast of Sweden," although I have seen 

 no list of such forms. I have already recorded it from 

 Gaslerosteus aculeatus (var. Iracliurus), and to this I have 

 to add Coitus bubalis, Cotlus scorpius, Gobius liutUensparri, 

 Centronotus gunncllus, Zoarccs viviparus. Mole/la muslela, and 

 Liparis Mo?ilagui. About 70 per cent, of the total number 

 of fish of these species examined were infected, usually with 

 three or more adult parasites and. often a large number of 

 young. Thus it may be understood that this form is ex- 

 ceedingly frequent. 



Olsson determines the length of his specimens at 3-9 mm. ; 

 Leviusen found somewhat smaller examples in Coitus scorpius 

 (3-5 mm.) ; Odhner gives the average length as about 

 2 mm., and is inclined to regard Olssou's larger specimens 

 as a variety. He also differentiates a medium-sized variety 

 corresponding with Levinsen's specimens and also with 

 Disl. rejlexum, Crcpl. My examples only in rare eases 

 exceed 3 mm., the majority being l"5-2"5 mm., so that as 

 far as length is concerned they correspond v/ith Odhner's 

 smallest variety, i. e. with the Rudolphi type. Fully de- 

 veloped adults were found as small as 1 mm. ; one small 

 example from the stickleback measured 1*01 mm., and 

 contained seven ova measuring "081 x "047 mm., i. e. of 

 fully normal size. The largest imruature individual observed 

 was '90 mm. in length; it contained no ova, but the penis 

 was well developed, and the testes were as large as "28 X 

 11 mm. 



The general shape of the body is elongate-OA^oid, depressed, 

 somewhat attenuate anteriorly, more rounded posteriorly. 

 Like the other species of the genus, it is extremely mobile, 

 the ant-acetabular region being capable of great extension 

 and contraction, the post-acetabular part less so, but the 



I 



