the Domestic Animals in Iceland. 181 



7". cosnurus in 1, T. serrata in 02, T. echinococcus in 0-4, T. cu- 

 cumerina in 48, Bothriocephnlus, sp., in 0-2, Ascaris marginata in 

 24, and Dochmius trigonocephalus in 2. 



The distinctive characters of the first three species, established 

 by Kiichenraeister and Leuckart, have been disputed by other 

 distinguished helminthologists ; but, by examining these Tsenias 

 carefully (as was done by M. Baillet at Toulouse), without know- 

 ing beforehand whence the worms originated, I convinced my- 

 self of their differences. In France M. Baillet has most com- 

 monly found T. serrata in dogs, and also frequently T. marginata; 

 but he never found T, ccenurus except in animals which had been 

 experimented upon. In Denmark T. serrata occurs but rarely, 

 which is explained by the fact that few rabbits are bred there. 

 Moreover, as regards the worms most commonly observed, I was 

 able to ascertain the influence exerted by the age and size of the 

 dogs, by the place which they inhabited, and their state of health. 

 Thus the frequency of Tania marginata increases considerably 

 with age, and in a still higher degree with the size of the dogs; 

 it is more common in the dogs of the suburbs than in those of 

 Copenhagen, and is less frequently met with in sickly than in 

 healthy dogs — facts which are explained by the mode in which 

 those animals acquire the T. marginata. 



The frequency of T. marginata^ ccenuruSj and echinococcus in 

 Iceland depends especially upon the great number of sheep 

 which the inhabitants possess, as their vesicular worms are the 

 cause of the development of these Tsenias in the dogs. Tcenia 

 canis lagopodis is a very remarkable species ; besides the dog, it 

 is found in the cat and the Isatis ; and, although mentioned by 

 Abildgaard, it has not yet been described. This worm has the 

 head unarmed, and is not furnished with genital orifices at the 

 edges of the joints, by which, combined with a peculiar con- 

 formation of the internal organs, it approximates to T. angus- 

 tata, T. litterata (a species still but imperfectly known), and 

 Mesocesto'ides ambiguus of Vaillant. As to the Bothriocephali, 

 those which 1 met with in the dogs of Iceland not only differed 

 from B. latus and cordatus, but also varied so much among 

 themselves that it is not without doubt that I venture to refer 

 them to the same species. Some of these worms, which, al- 

 though of considerable size, were completely destitute of genera- 

 tive organs, presented a mode of development of the joints quite 

 unknown among the Taenias, but which has been indicated in some 

 Bothriocephali by Eschricht and Siebold. I refer to the increase 

 of the number of joints by means of the secondary transverse 

 division of the formed joints, a division which may even be re- 

 peated. Something analogous to this occurs also in various 

 species of Bothriocephali inhabiting the intestines of the Seals, 



