Entozoa of British Mtrine Fishes. 77 



from ova as near tic terminal portion of tlie uterus as 

 ])ossible. Linton's fi^'uns for the ov;i of his Ameriean 

 specimens are "OSl X 'Ol' nun., so that they also correspond 

 with other observations. 



This parasite is usually confined to tlic intestine of its 

 host, th()ii<;h occasionally one or two specimens art; to be 

 found in the stomach and in one host (Gadns me I a no a to inns), 

 accordiufi: to Olsson, it occurs in the pyloric c;eca. 



While studying this form, I examined sticklebacks from 

 three diflerent rej^ions, viz. (1) rock-pools, (2) brackish 

 ditches communicating with the sea, (3) streams near their 

 entrance into the sea. lu the first two instances 1 obtained 

 Gaslvruslnts avuleatns, var. trachnrus ; in the third, var. 

 gynutiirns. The river sticklcl)aeks were much smaller than 

 those from the sea, and in no case did they harbour Podo- 

 cotyle atoinofi. The si)ccimens from the pools and ditches 

 were identical and were each equally subject to infection. 



Levinsen asserts that the intermediate host of Distomum 

 sivip/cx is Thcmisto Ubelliila. This crustacean is not recorded 

 from the St. Andrews district, so that it cannot be the 

 iutermecliatc host here. 



Lepodora rach'KBa^ Cobbold*. (PI. I. figs. 3, 4.) 



Distomum rachion, Cobbold, Tians. Liun. Soc. xxii. p. 158, pi. xxxi, 

 ti<j8. l>, 10; Stossicli. Dist. d. Pesci, p. 4o ; Lintun, Proc. U.S. Nat. 

 Wus. .XX. p. o38, pJ. liii. figs. 3-7. 



Lepodora rachiaa, Udbiier, Fauua Arctica, iv, (2^ p. 332, pi. ii. 

 ligd. 12-l.j. 



To reconcile CobbokVs figure of Distomum rachion with 

 the one\>liich 1 herewith submit seems at first sight difficult. 

 The disposition of the genital glands and uterus appears to 

 eftectually separate them. The resemblance in other respects, 

 however, is striking enough, and as it is possible to interpret 

 correctly the structures misrepresented by Cobbokl, I have 

 little doubt that his specimens and mine are identical, and 

 this is endorsed by the facts that the organization of the 

 parasite is definitely characteristic and that Gadus (Cfjlejinus 

 figuics as the host in both instances. 



Cobbold^s description is embodied in a few lines, but this 

 brevity is remedied by a boldly drawn figure. In inter- 

 preting this figure we must supjjose either that he drew from 

 ihe living animal, when the thickness of the body would 

 jirevent him seeing clearly the organs in the posterior part, 

 or that his preserved specimens were not sutUeiently cleared. 



• Odhner's amended descriptions of this species and otLtrs did i:ot 

 come to band until the present paper •was in tlie press. 



