Mr. H. J. Carter on Microscopic Filaridse. 109 



males perish, for a male Guinea-worm here is unheard of; and 

 from whence the one figured by Prof. Owen came is not men- 

 tioned. 



Mr. Lubbock's obseiTations*, however, show that the female 

 organs of generation may throw oiF buds at one time and ova at 

 another ; so that Filaria Medinensis may not require to be im- 

 pregnated to bring forth its progeny. 



However this may be, Filaria Medinensis is viviparous, and all 

 her progeny are of the same size when she puts forth her head 

 from the surface of the body; while Mermis albicans, which is 

 closely allied to Filaria Medinensis, enters the larvse of the Le- 

 pidoptera as an embryo, and leaves them at full growth, but 

 before it has acquired the organs of generation f. The Filaria 

 which I saw in Nais albida were all females ; and their oviducts 

 were filled with ova in successive stages of development, each of 

 which was provided with its germinal vesicle and nucleus, and 

 none without it ; so that while these Filarice thus difi^ered from 

 Mermis albicans, they too might nevertheless have been about 

 to leave their host, in some way or other, for impregnation. 



If Filaria Medinensis be propagated by its young ones, and 

 these enter the human body directly after they leave the parent, 

 they must enter it unimpregnated, for there is no trace of the 

 generative organs to be seen at the time of their birth ; while, 

 if they enter it afterwards, they must be born in water (for they 

 would die out of it), and remain there until the organs of gene- 

 ration are developed, — to which, again, their want of power in 

 sustaining life is opposed. 



On the other hand, if it be one of the Urolabes which becomes 

 Filaria Medinensis, and it enters the body after the organs of 

 generation have become developed, this is quite contrary to what 

 takes place with Mermis albicans and other free Filaridse, which 

 enter the bodies of the animals or insects which they infest in 

 their embryo state, and leave them before the organs of genera- 

 tion are developed. But supposing that one of the Urolabes 

 which I have described entered in a mature state, the smallest 

 would have to bore directly through the skin ; for it is twice the 

 diameter of the mouth of one of the sudorific ducts, estimating 

 the latter at the 1200th part of an inch in diameter, — and if 

 Urolabes palusiris, this is three times the diameter at least. It 

 is true that there may be still other species of Urolabes which 

 are much smaller, and in their mature state do not exceed the 

 diameter of the orifices of the sudorific ducts ; but even then 

 it must be remembered that they have to take in with them a 

 sufficient number of spermatozoa to impregnate the whole of 



• " On the Hybernating Eggs of Daphnia," Phil. Trans. 1857. 

 t Ann. des So. nat. t, iv. p. 68, 1855. 



