DEVELOPMENT OF THE GENERATIVE ORGANS. 711 



this heap of cells soon grows into the form of a longitudinal band, 

 while in the cystic tape-worms it extends transversely in correlation 

 with its subsequent structure. 



This growth continues for some time without any other modifica- 

 tion. In stained preparations of the larger tape-worms (both Tcenia 

 saginata and Bothriocephalus latus) this structure is seen some centi- 

 metres behind the head, shining through the cortical layer of the 

 body. In this state the rudiment in Bothriocephalus was formerly 

 detected and examined by Eschricht. It seemed at first, however 

 and with this my account of the rudimentary reproductive organs in 

 T. saginata (p. 446) should be compared as though the rudiment 

 directly formed the efferent apparatus alone, and as though the germ- 

 producing organs originated independently, and became afterwards 

 associated with the former. 



Subsequent investigations have, however, convinced me that this 

 opinion is not correct, but that the germ-producing organs also owe 

 their origin to the cells of the primitive rudiment. I can, it is true, 

 affirm this with perfect certainty only of the ovary and yolk-gland of 

 Tcenia, but the fact that the vasa efferentia, or at least their larger 

 branches, owe their origin to radiations from the vas deferens, suggests 

 that the above statement holds true also of the testes. That the genetic 

 connection between the germ-producing organs and the primitive 

 rudiment is less distinct than that between the latter and the efferent 

 ducts, as is certainly the case, is due to the fact that the latter appear 

 as more massive structures, and exhibit at an early stage a definite 

 boundary. 1 



What I have to communicate with regard to Bothriocephalus in 

 this connection is unfortunately very incomplete, and indeed little 

 more than a repetition of the results of Eschricht. 



I would first note that the primitive state of the reproductive 

 rudiment persists for some time without marked change. At a distance 

 of about 10 cm. behind the head, the rudiment is still seen as a dark, 

 indistinctly defined, longitudinal streak, extending in the median line of 

 the joints. Three or four centimetres farther back the contours become 

 sharper, and one can detect at the anterior end of the streak, close 

 behind the margin of the joint, a roundish aggregation of cells seated 

 on the others like a sort of head. This structure mainly represents the 

 hitherto incompletely separated rudiment of the genital ducts and the 

 associated efferent apparatus, organs whose differentiation and forma- 

 tion occupy a length of 15 cm. Fifty centimetres behind the head, 



1 From this one can see how inconsistent it is for Moniez to deny the morphological 

 independence of the germ-producing organs in the Cestodes, and to refer both ova and 

 spermatozoa to the direct modification of ordinary parenchymal cells. 



