156 DR. T. S. COBBOLD ON ENTOZOA. 



Auk, Alca torda. Rabbit, Lepus cuniculus. 



Red-throated Diver, Colymbus septentrionalis. Dog, Canis familiaris. 



Golden Pheasant, Phasiamts picius. Lion, Felis leo. 



Capercailzie, Tetrao urogallus. Ox, Bos taunts. 



Sheep, Ovis cries. 



Mouse, Mus musculm. Giraffe, Camelupardalu giraffa. 



Cat, Felis catus. Porpoise, Delphinus phoccena. 



In this list, notwithstanding the imfavourable circumstances above alluded to, I have 

 found no less than sixty forms of Entozoa infesting forty-five vertebi-ate species ; and there 

 cannot be the slightest doubt, as subsequent observations wDl show, that this figure affords 

 but a very low estimate of the liability of invasion to which these creatures are exposed. 

 It is also worthy of remark, that out of those species in which Entozoa were not found, 

 only one belonged to the fish tribe ; whereas a very careful examination failed to detect 

 any worms in several kinds of birds and mammals. Among those species not harbouring 

 Entozoa, but in which their presence might have been anticipated, were the following : — 

 WUd Duck, Swan, Woodpecker, Starling, Pheasant, Tawny Owl, large Water Newt, Water 

 Rat, Squirrel, Stoat, Otter, Badger, Fox, and common Brown Bear. 



Six or eight species of Entozoa have been described as inhabitkig Gasterosteus aculeatus, 

 but I have only met with three ; namely the Tmnia filicolUs (PI. XXXI. fig. 1) ; an imperfect 

 specunenof cestoid worm corresponding in some respects vsdth theScMstocejihalus dimorphus 

 of Creplia, and a small trematode presumed to be the Monostoma caryophyllinum in a very 

 young state (figs. 2, 3). The head of T. filicollis, according to the descriptions of Dujardin 

 and others, is simple, globular, unarmed with the usual proboscidiform retractile tubercle, 

 and improvided with lateral suckers. In those which have come under my notice, a very 

 distinct proboscis was to be seen whUe the specimens remained fresh, but there was no 

 indication of hooks ; these may have fallen off. Pour well-developed suckers surrounded 

 the head, and the water-vascular canals were imusuaUy conspicuous throughout the 

 entire segmental series. In an adult individual, these tubes, four in number, terminated 

 superiorly so close to the cup-shaped bothria, that it was difficiilt to divest oneself of the 

 notion that they communicated with the latter. 



After a fruitless search for Entozoa in many specimens of Gasterosteus spinachia, one 

 example at last yielded an extremely minute trematode (figs. 4, 5), enclosed in a cyst of 

 cellular tissue and attached to the subperitoneal surface of one of the ovaries. While 

 under microscopic examination it was accidentally swept off the slide, but an outline of 

 its structui-e has been preserved. A feature in this specimen consists in the presence of 

 an unusually large ventral appendage, the free extremity of which is bifid and each 

 division apparently perforated. The hermaphroditic signification of this organ is evident ; 

 but the cu'cimistance of the ends of the male and female reproductive tubes being thus 

 greatly extended, may in some measuj-e be regarded as accidental. Traces of a bifurcate 

 stomach were plainly discernible, the canals being slightly sinuous. As I am unable to 

 refer this worm to any known species, I recognize it provisionally under the signification 

 of Ilonostoma dubium. 



In Motella quinquecirrata — the Gadus mustela of Linnaeus — Eudolphi mentions the 



