SPECIFIC AND INDIVIDUAL DIFFERENCES. 733 



We must, however, remember that the specimens of Bothriocephalus 

 latus occurring in the dog and cat not only develop much more slowly 

 than in man, but differ more or less strikingly in size. It is true that 

 the worms in man have not always the same appearance. This is 

 sufficiently evident from the fact that, besides the real and typical 

 Bothriocephalus latus, or in place of the latter, both the earlier and 

 more recent Helminthologists have thought themselves justified in 

 distinguishing several different species. Thus Linne* spoke of Tcenia 

 vulgaris and of T. lata ; Pallas of T. grisea, T. lata, and T. tenella ; 

 Goze of T. memlranacea and T. lata all of which, although regarded 

 as Tcenice, belong to Bothriocephalus latus. 



These species were distinguished, not only on account of the false 

 ideas which then prevailed regarding the structure of the head in 

 Tcenia lata, but especially on account of the different physiognomy of 

 the worms, and the structure of their joints and uteri. Although 

 Grassi * has lately tried to identify with Linnets Tcenia lata the Both- 

 riocephalus cordatus discovered by me, which we shall afterwards more 

 specially consider, I must continue to regard it as a distinct species. 

 On the other hand, I think that, notwithstanding its inconsiderable 

 length (1-8 metre), and the smallness of its joints, the form described 

 by the latter (without name), and also the Bothriocephalus cristatus of 

 Davaine, ought to be regarded as belonging to B. latus. 



The differences which can be observed in the worm are to be re- 

 ferred partly to an unequal state of contraction, and partly and more 

 especially to differences in age, growth, and food. As Botticher has 

 already noted, there are " well-fed " worms, and others which are 

 extremely emaciated and appear as thin as paper. The former are 

 more or less coloured, yellowish or yellowish-brown, according to the 

 distention of the yolk-glands, while the latter are colourless, and have 

 but slightly developed sexual organs with few eggs. In the same 

 way there are large and small Bothriocephali ; some, with a size of 2 

 metres or even less, attain their full development, as is evident from 

 the fact that in them the greatest breadth and greatest distention of 

 the uterus do not coincide with the end of the chain, but usually 

 occur some distance anterior to this, at least if a number of proglottides 

 have not previously been cast off. Moreover, such examples are not only 

 shorter than the average, but their joints are smaller, having a length 

 of 2 to 2'5 mm., and a breadth of perhaps 5 to 6 mm., while usually 

 the latter is double this, or even more (as much as 20 mm.). Thus it 

 happens that the relations of length and breadth in the joints often vary 

 throughout considerable portions, or even throughout the whole of the 

 body ; and under some circumstances the length of the joints becomes 



1 " Intorno ad un Bothriocephalus dell' uomo," Ann. univ. di Meet., vol. cell., p. 8. 



