104 Mr. H. J. Carter on Microscopic Filaridae. 



two parallel halves if cut in two in the centre ; but at the same 

 time, the ovisac being continuous, uniform in size, and without 

 constriction or projection throughout (fig. 2), besides extending 

 with the ovarian tubes from one end of the body to the other, 

 the whole differs very considerably from the organs of genera- 

 tion of Urolabes palustris, which only occupy the middle half, 

 are inflected upon themselves, present a line of demarcation 

 between the ovary and ovisac and the fallopian tube, and a con- 

 striction in the latter where it unites with its fellow to form the 

 vagina (fig. 8). 



Such are the identities and differences between Filaria Medi- 

 nensis and Urolabes palustris. We have now to consider how 

 far the latter are real, or the result of the circumstances under 

 which Filaria Medinensis is developed, — that is, compelled to 

 receive support from the surrounding tissues of that part of the 

 human body in which it may be situated, and to retain the 

 whole of its progeny until they are all equally and sufficiently 

 developed for delivery. 



Undoubtedly the shrunken state of the alimentary canal 

 throughout, together with the insignificant development of the 

 parts about the mouth, to which I have already alluded, and the 

 apparent obliteration of the anus in the adult Filaria Medinensis, 

 compared with the enormous development of the tegumentary 

 and muscular systems, and that of the organs of generation, 

 indicate that the former has not only not kept pace with the 

 latter, but that it has hardly been called into action at all for 

 the development of the organs of generation, &c. ; and this is 

 further confirmed by the fact that the head of the adult Filaria, 

 always projecting first and perishing, obliterates the mouth, and 

 thus leaves the rest of the body to be nourished and kept alive 

 (which it is, with all the remaining part of the progeny, up to 

 the last inch) through its surface, which nourishment must 

 come from the tissues of the body, and still further by the pre- 

 sence of delicate filaments of cellular tissue adherent to the body 

 of those worms which are extracted by surgical operation before 

 they have begun to protrude of themselves. For the same 

 reason, viz. the want of use, probably arises the diminutive and 

 inflected state of the tail, fixed also to the body by an adven- 

 titious membrane ; while the instinctive power which presides 

 over the development of the body generally, knowing that a 

 vaginal orifice for impregnation and the exit of the ova would 

 not be required, seems to have arrested the form of the organs 

 of generation at that point where they consisted merely of a 

 cylindrical sac with ovaries, though it allowed the increase in 

 size of these to go on up to that degree which would be suffi- 

 cient to accommodate the whole of the progeny. 



