Mermis Parasitic on Ants of the Genus Lasius. 



367 



similar organ has been seen in a stained whole preparation of a 

 newly-emerged larva. This is the only evidence we have been 

 able to obtain, up to the present, of the existence of males. No 

 adult males have been found among the individuals that we have 

 succeeded in rearing to maturity. The females, however, produce 

 numbers of fully-formed eggs capable at least of going through 

 the process of segmentation, and the question arises whether we 

 have here a case of protandrous hermaphroditism, or whether, in 

 the absence of males, the females are capable of reproducing 

 parthenogenetically. Instances of both these conditions are to be 

 found among nematodes, though we know of no record of them in 

 this comparatively little-known family. It should be mentioned. 



Olmnv. 



Fig. 8. — Mermis myrmecophila. Head of same individual as in Fig. 1 ; lateral 

 view. Lettering as in Fig. 1, with the addition of vi, mouth, and s.v.p. 

 subventral papilla of right side. 



however, that in the present species no evidence is available of 

 the existence of both male and female organs or germ-cells in the 

 same individual ; while the evidence for the total absence of males 

 among the adults cannot yet be regarded as conclusive. 



The larvte, which emerge from the ants during the month of 

 July, enter upon a period of free existence lasting for six or seven 

 months, during which they probably undergo at least two moults. 

 Our specimens completed their last moult during the month of 

 January. 



It is a curious fact that the female organs are fully developed, 

 and contain many eggs apparently ready for laying, some time 

 before the last moult. That is, the worms are to all appearance 

 sexually mature and capable of reproduction while still in the 



