goze's two varieties of tape-woem. 417 



solium — he mentions, after Pallas' example, besides the "large and 

 strong " and the " ilat, delicate, and transparent " varieties, a third 

 one, namely, " the cucumber tape-worm of the dog " {T. serrata, Eud.), 

 which " ought not to be omitted, if the other two are explained as 

 mere varieties." The differences between these forms, and especially 

 between the first two, are, he teUs us, very constant, and noticeable even 

 in the formation of the branch-like division of the ovary, " although he 

 wQl not venture to define them." He adds, further, that they have 

 no connection with the constitution of their host, but that it rather 

 appears as though the degree of frequency of both varieties were 

 determined by the locality. 



Later helminthologists have devoted less attention to the fore- 

 going varieties of form, partly indeed because (being for the most part 

 North Germans, especially Eudolphi) they lived and collected in 

 districts where they mainly came across only one form. Their Tcenia 

 solium is pre-eminently the hook-bearing species still designated by 

 this name. It is true that the great variability in the size and nature 

 of the joints was sometimes noted, but it was not perceived that these 

 divergences always occurred only in certain individuals, and charac- 

 terised particular " genera " or " varieties," which we are now accus- 

 tomed to regard as distinct species. 



But of course the less this circumstance was noted, the more sur- 

 prising did it seem that reports multiplied, according to which the 

 head of the human Tcenia was sometimes destitute of the circlet of 

 hooks. It gradually began to appear as though there were, as Batsch 

 had already conjectured, districts, or even whole stretches of country, 

 in which Tcenia solium was never, or only very seldom, found with an 

 armed head. 



Thus Bremser, the famous Viennese helminthologist, reports in 

 liis great work^ that, in opposition to the general descriptions and 

 figures of Tcenia solium, he had sought in vain for the circlet of hooks, 

 and that, in spite of the most minute examination of a great number 

 of tape-worms (in Vienna), he had only seen it in a head sent by 

 Eudolphi from Berlin. A worm with a hook-bearing head was after- 

 wards sent to him from the general hospital. If Bremser had paid 

 attention to the fact that the unarmed worm which he had observed 

 also differed from the armed one in size and structure of the joints 

 (all of his drawings very closely represent Tcenia saginata), the 

 explanation of the lack of hooks might perhaps have been sought in 

 another direction than in the supposition (adopted by other investi- 

 gators, and especially by my uncle, F. S. Leuckart, and Mehlis) that 

 the tape-worm lost its armature with age, as a man loses his hair. 



