1000 MR. F. E. BEDDARD OX 



if we are to regard the ovary as ventral, they lie to the dorsal 

 side. 



The vaginal pore lies behind the opening of the male duct 

 into the genital cloaca. The vagina is a perfectly straight, delicate- 

 walled tube as in so many tapeworms. Posteriorly and close to 

 the lateral water-vessel, the vagina expands into a somewhat pear- 

 shaped receptaculum seminis, from the wider, posterior end of 

 which the vagina emerges again abruptly and runs a curved oblique 

 course towards the ventral side of the body. This latter region 

 of the vagina is of the same calibre and appearance as the 

 terminal section which opens into the genital cloaca. The 

 swollen receptaculum seminis (text-fig. 206, p. 998) has on the other 

 hand thick glandular walls. The ovary and the yolk-gland lie 

 anteriorly in each proglottid and very nearly in the middle of 

 the proglottid, verging however to the pore side, the position 

 being therefore quite difi'erent from that which characterises 

 Thysanotcenia gambiana. The ovary is not large, neither is the 

 yolk-gland. 



Whether a uterus exists as a definite structvire at any period in 

 the development of the sexual organs, I am not able to state with 

 certainty. But I am disposed to think that a distinct uterus 

 does not exist. At the most, it must have a very brief existence, 

 for I can find nothing intermediate between eggs scattered in the 

 parenchyma and in the paruterine organs. I foiuid nothing like 

 what has been described in Thysanosoma. In this genus thei-e 

 are stated to be outpocketings of the uterus round each of which 

 is formed a paruterine organ. I found in the present species a 

 condensation of the parenchyma round eggs or groups of eggs, 

 precisely as I have desci'ibed in Thysanotcunia gambiana. These 

 latter became more marked, and were then to be described as paru- 

 terine organs. In fact, the state of affairs which characterises the 

 genus Thysanotfenia is to be looked lapon as a further stage in 

 the development of such a genus as Oochorisiica with the inter- 

 mediate formation of a uterus dropped out, or at least rendered 

 of very little importance. It is also like Davainea 



Text-figure 207 represents a transverse section through a fully 

 mature proglottid of this worm. It may be compared with a 

 corresponding illustration of the other species of the genus, 

 Thysanotcenia gambiana*, when certain differences will be 

 apparent coupled naturally with fundamental points of agreement. 

 In both species, the greater part of the medullary region of the 

 segment is occupied by the numerous paruterine organs, which 

 are only one layer deep. They extend between the excretoiy 

 vessels and up to those vessels on either side. In Thysanotcenia 

 lemuris, however, the transverse row of paruterine sacs is at most 

 thirteen to sixteen, while they are much more numerous in 

 Th. gambiana. Furthermore, in a given section the greater number 

 by far — ^very often all — of the paruterine organs are seen to be 



* P. Z. S. 1911, text-fig. 158, p. 058. 



