156 : DR. T. S. COBBOLD ON ENTOZOA. 
Auk, Alca torda. Rabbit, Lepus cuniculus. 
Red-throated Diver, Colymbus septentrionalis. Dog, Canis familiaris. 
Golden Pheasant, PAasianus pictus. Lion, Felis leo. 
Capercailzie, Tetrao urogallus. Ox, Bos taurus. 
Sheep, Ovis aries. 
Mouse, Mus musculus. Giraffe, Camelopardalis giraffa. 
Cat, Felis catus. Porpoise, Delphinus phocæna. 
In this list, notwithstanding the unfavourable circumstances above alluded to, I have 
found no less than sixty forms of Entozoa infesting forty-five vertebrate species; and there 
cannot be the slightest doubt, as subsequent observations will 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 :— 
Wild 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 inhabiting Gasterosteus aculeatus, 
but I have only met with three; namely the Tenia filicollis (Pl. X XXI. fig. 1); an imperfect 
specimen of cestoid worm corresponding in some respects with the Schistocephalus dimorphus 
of Creplin, 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 unprovided with lateral suckers. In those which have come under my notice, a very 
distinct proboscis was to be seen while the specimens remained fresh, but there was no 
indication of hooks; these may have fallen off. Four well-developed suckers surrounded 
the head, and the water-vascular canals were unusually 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 difficult 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 structure 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 circumstance of the ends of the male and female reproductive tubes being thus 
greatly extended, may in some measure 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 Monostoma dubium. 
In Motella quinquecirrata—the Gadus mustela of Linnæus—Rudolphi mentions the : 
