558 DR. F. E. BEDDARD ON 



me that we must come to the conclusion that a growth of the 

 medullary parenchyma between the individual eggs produces the 

 final result seen in the terminal and penultimate proglottid of 

 the specimen which I have studied. It might be argued that 

 this process is really comparable to the formation of paruterine 

 organs which are growths of medullaiy tissue encapsuling the 

 eggs though with histological change. In Dipylidimn we have 

 no histological change, but all the same encapsuling growths of 

 parenchyma. 



Having given an account of the structure of this D'qyjjlidium, 

 it remains to be decided whether it be a new species or identical 

 with one of those already described. It is, as I think, hardly 

 necessary to say much of D. cctninum, with which there can be no 

 possibility of confusing the present species. The much greater 

 size of that species and the form of its uterus at once distinguish 

 it from that which is the subject of our present communication. 

 It seems indeed to me that the genus Dijjylidhmi I'equires really 

 division into two genera — D. caninum belonging to one, and all 

 the other species that are adequately known to the other. It is 

 from the latter that it is not so easy to distinguish D. dongolense 

 of the present paper. If D. geneitce of Gervais * and B. gervaisi 

 of Setti were not much larger .species than mine, I should have 

 been inclined to identify it with one or possibly both of them. 



D. echinorhynchoides (from Megcdotis cet'da) is much larger than 

 my species, has a much longer rostellum and a longer neck. 

 D. trinchesii is a smaller species, but still considerably larger 

 than D. dongolense, measuring 2*5 cm. ; it has, however, a 

 short rostellum, like that of my species ; but it is to be 

 distinguished by the greater length of the mature segments, 

 which do not ovei'lap, and the invariable inclusion of each ripe 

 ovum in a separate compartment. Though a receptaculum 

 seminis is said to be present, it is hardly represented in the 

 figure t. D. pasqualii, on the other hand, has an obvious recep- 

 taculum J, but it is a much larger species, i.e. 200 mm. The 

 uterus is as in the last, and therefore differs from that of D. don- 

 golense ; but it is to be noted that the ripe ova extend into the 

 cortical layer, as do the egg-chambers of D. dongolense. Occurring 

 as it does in the intestine of a closely allied species, it might be 

 expected that D. gervaisii of Setti § would be more closely allied 

 to D. dongole7ise than the other species of Dipylidium referred to. 

 It is not, however, as it would appear, any nearer in structui-e. 

 For in this species, as in most others, the ripe ova are figured as 

 embedded sepai-ately in the parenchyma, without any previous 

 inclusion in larger cavities. It is also rather larger, being from 

 1-4 cm. in length. 



Nor can the present species be confused with D. zschokkei \\. 



* Mem. Ac. Sci. Moiitpellier, 1847. 



•f Diamare, loc. cit. pi. i. fig. 9. % Loc. cit. pi. i. fig. 8. 



§ " jDijii/lidium gervaisii," Atti Soc. Lig. Sci. Nat. vi. 1895. 

 II Hungei-biihler, "Studien au Gyrocotyle iind Cestoden," Denkschr. Ges. Jena, 

 xvi. 1910, p. 516. 



