398 FAMILY T^NIAD^-. 



almost all the instances. We shall afterwards return to these structures, 

 and will only now note that they have occasionally been described as 

 distinct species, as, for example, the Twnia froni the Cape of Good 

 Hope distinguished by Ktichenmeister, and the Tcenia lophosorm of 

 Cobbold. 



Whether these malformations are hereditary, as Kiichenmeister 

 supposes, must remain undecided till it is settled experimentally. But 

 what we know of the occurrence of six-rayed bladder-worms is only in 

 favour of a spontaneous origin, since they are always found singly among 

 normal specimens which probably originated from the same brood. In 

 Ccenurus the six-rayed heads are found even on the same bladder as 

 the four-rayed,^ as one may conclude from the fact that, after "feed- 

 ing" I found in a dog one six-rayed (or triangular) tape- worm — but 

 one only — among the numerous specimens with foiir suckers.'' 



Even the hooks sometimes undergo sundry malformations besides 

 the variations in number above referred to. These concern both the 

 root-like processes and the claws, and are sometimes so marked that, 

 instead of the proper hooks, only more or less irregular chitinous 

 knobs, in which one can at first glance hardly recognise the charac- 

 teristic and beautiful head armature. In the cases I have seen these 

 malformations mostly concern the whole circle of hooks, so that their 

 conditions must be sought rather in the common place of attachment 

 than in the individual papillae. Even a total abortion of the circle of 

 hooks has been observed. 



The numerous abnormalities of the proglottides we shall have further 

 opportunity of studying. They are abundant enough, especially in 

 Tcenia saginata, but may be for the most part reduced to a sometimes 

 luxuriant, sometimes imperfect, or even wholly absorbed segmentation. 

 Occasionally one meets with tape-worms in which a second segment 

 is found laterally attached. The supernumerary segment is in such 

 cases usually partly abortive, though the contrary also occurs. Moniez 

 describes a case of Tcenia marginata which forked in two places,^ 



1 This fact contradicts Moniez's supposition (BvU. Sci. dep. du Nord, p. 202, 1878) 

 that such a head might result from a twelve-hooked embryo, such as he had often observed 

 (see p. 330). 



^ My experience of trianglar tape-worms is not exclusively limited to this one 

 case, but also includes two other cases of Tcenia saginata. One of these, viz., Kuchen- 

 meister's T. capensis, I have formerly described (First German edition of this work, 

 Bd. i., p. 308). 



" " Observations t^ratologiques chez les T6nias," loc. eit., p. 201. I may also mention 

 that Moniez has at different times observed that T, expansa, and once the T. denticulata 

 found along with it, were infested with Psorospermiae. What Moniez has so designated is 

 not, however, in any way a Sporozoon (see p. 191), but a so-called Micrococcus {Panhisto- 

 phyton), and therefore a fungus, similar perhaps to those which I once found in Oxyuris 

 see Vol. II.), and which Biitschli has also found in free-living Nematodes. Moniez also 

 reports finding his Psorospe^^ffg^jl^/^^/g.^igjIgO^s. 



