UNCINARIA. 167 



inability to absorb nourishment, due to the diseased condition of the intestinal 

 mucosa. Whether the parasites produce a specific poison which affects the host is 

 still an open question ; the intense inflammation of the small intestine can easily be 

 explained by the wounds produced by the buccal armature. 



We at present see no possible outlook either in the line of treatment or prevention, 

 so far as this disease in the seals is concerned. In man thymol is a specific. It is 

 difficult to disinfect against the eggs of the genus. 



The symptoms and pathological lesions in various animals will be described in 

 the later paper.^ 



Life History. — In the case of two species ( U. vulpis and U. duodenalis) it has 

 been experimentally demonstrated that these worms are autoecious parasites — that is, 

 that they require no intermediate host for their development. The life cycle, which 

 will be given more in detail later, is essentially as follows: The eggs laid by the 

 parasitic females are in the first stages of segmentation; upon being passed with the 

 faeces they develop into a rhabditiform embryo, the time required varying from twelve 

 hours to twelve days or more, according to the conditions of the medium in which they 

 are found, the temperature and the accessibility of air; the eggs find their most 

 favorable conditions in the superficial portion of rather compact faecal matter. The 

 embryos, which measure about .0.3 mm. in length, take nourishment, and after about 

 two or three days undergo the first ecdysis, during which the pointed tail is partially 

 lost. A second ecdysis begins about five to seven days after the escape from the egg, 

 and the worm is soon ready to enter upon its parasitic life; it has lost its rhabditiform 

 character and with its ability to take food during its free life. About five days after 

 entering their host (by means of drinking water or contaminated food) the worms 

 submit to a third ecdysis, during which a provisional buccal capsule is formed. A final 

 (fourth) ecdysis then occurs, four to ten days later, which transforms the parasite into 

 its definite form. About four to five weeks appear to be necessary for the development 

 from the egg to the fully mature stage. 



There is no reason to assume that the, life history of the seal Uncinaria will be 

 materially different from the life history of U. vulpis and Z7, duodenalis, but slight 

 variations in the length of the different stages may occur because of the colder 



climate. 



IV.— Family BOTHRIOCEPHALIDAE. 



DiAGsrosis.^Cestoda ; head provided with two groove or slit-like suckers; rostellum wanting; 

 uterus with special pore; genital pores generally dorsal or ventral. 

 Type. Bothriocephalua Kudblphi, 1808. 



Subfamily BOTHRIOCKI'II^LIlSrA.K. 



Diagnosis. — Bothriocephalidae with distinct external segmentation ; head with two elongate 

 slit or groove-like suckers. 



Type. Bothriooephalus Rudolphi, 1808. 



Genus BOTHRIOCEPHALUS' Rudolphi, 1808, emend. R. Blanehard. 



Diagnosis. — Bothriooephalinae with two suckers; penis, vulva, and uterus open ventro-niedian. 

 Type. S. latus^ (Linnaeus, 1758) Bremser. i 



' See pp. 77-82 of this volume, where the subject is discussed by Lucas. 



* We fail to see how this generic name can be held for the group to which it is now assigned; 

 certainly B. latus can not be taken as the type of Bothriocephalua. We refrain from attempting to 

 straighten the synonymy, as a number of names are involved and ii proper interpretation of the 

 genera demands a most cautions revision of the entire family. 



