CESTODA 



111 



abnormalities of structure, the proglottides frequently displaying 

 double sexual orifices, with corresponding duplication of the 

 reproductive organs internally. For details respecting the 

 anatomy of Bothriocephalus I must refer to the works of 

 Kiichenmeister and Leuckart ; and more particularly to the 

 memoir of Drs F. Sommer and L. Landois, who have supple- 

 mented the previous researches of von Siebold, Leuckart, 

 Bottcher, Stieda and others by beautiful investigations of their 

 own. In the pages of ' Nature/ for 1872, I gave a resume of 

 Sommer's memoir, which will be found quoted below. 



Bothriocephalus cordatus, Leuckart. This species is identical 

 with a worm long ago described by Pallas and Linneus. At 

 present it is only known to infest the residents of North Green- 

 land, but it is probably distributed throughout the north gene- 

 rally. It attains the length of about one foot, and has a small 

 heart-shaped head, whose apex is directed 

 forwards. The neck is so obscure that it 

 may be said to be altogether wanting, the 

 segmentation of the body being well marked 

 immediately below the head. Though so small 

 a species, Leuckart, who first described it, 

 counted between six and seven hundred joints. 

 As in the broad tapeworm, the reproductive 

 orifices are serially disposed along the centre 

 of the ventral line, but a close inspection 

 shows that the folds of the egg-bearing organ 

 are comparatively more numerous. This 

 worm does not appear to be a frequent 

 resident in the human body, though it is by 

 no means uncommon in the dog. Possibly 

 it may yet be found in the inhabitants of 

 some of our northern and western isles. 



Bothriocephalus cristatus, Davaine. This 

 cestode measures between nine and ten feet 

 in length, and is characterised by the 

 presence of two remarkable prominences, 

 together forming a sort of rostellum or 



, . , . T T FIG. 28. Head of Bothrio- 



crest which is covered by numerous minute cep hains /</*, viewed 

 papillse. The full-grown segments are less JgJJJ 8 ' 

 than half an inch in breadth; the body 

 of the parasite being narrower than that of the broad 

 species. The original description of the parasite by Davaine 



