THE VASA EFFERENTIA. 509 



extremely hazardous. If, however, this body really is the 

 remnant of a segmental opening, it would be reasonable to con- 

 clude that the vasa efferentia are buds from the segmental tubes 

 as opposed to their openings ; a mode of origin which is not 

 incompatible with the discoveries of Dr Spengel. I have noticed 

 a remnant, somewhat similar to that in the Scyllium embryo, 

 close to the hindermost vas efferens in an embryo Squatina 

 (PI. 20, fig. 8, r. st ?). 



With reference to the development of the longitudinal canal 

 of the Wolffian body, I am without observations, but it appears 

 to me to be probably a further development of the outgrowths 

 of the vesicles of each segmental tube, which were described in 

 connection with the development of the segmental tubes, p. 492. 

 Were an anterior outgrowth of one vesicle to meet and coalesce 

 with the posterior outgrowth of the preceding vesicle, a longi- 

 tudinal canal such as actually exists would be the result. The 

 central canal of the base of the testes and the network connected 

 with it in the adult (PI. 20, fig. 4), appear to be derivatives of 

 the vasa efferentia. 



I am thus compelled to leave open the question of the real 

 nature of the vasa efferentia, but am inclined to regard them as 

 outgrowths from the anterior segmental tubes, though not from 

 their open terminations. 



My views upon the homologies of the various parts of the 

 urinogenital system, the development of which has been described 

 in the present chapter, have already been expressed in a paper 

 on Urinogenital organs of Vertebrates 1 . Although Kolliker's 2 

 discovery of the segmental tubes in Aves, and the researches of 

 Spengel 3 , Gasser 4 , Ewart 6 and others, have rendered necessary 

 a few corrections in my facts, I still adhere in their entirety to 

 the views expressed in that paper, and feel it unnecessary to 



1 Journal of Anatomy and Physiology, Vol. X. [This edition, No. vn.] 



2 Entwicklungsgeschichte des Menschen u. der hoheren Thiere. 



3 Loc. cit. 



4 Beitrage zur Entwicklungsg. d. Allantois d. Muller 'schen Gange u. d. Afters. 



6 "Abdominal Pores and Urogenital Sinus of Lam prey, "Journal of Anatomy and 

 Physiology, Vol. X. p. 488. 



