NEMATODA MERMITHIDAE 



the intestine, and leaving the body of their host through the 

 anus, find their way to the earth. Here, according to zur 

 Strassen, the females die without playing any part in the per- 

 petuation of the species. The males, on the other hand, having 

 developed spermatozoa whilst in the larval stage (paedogenesis), 

 afterwards form ova, and are in fact protandrous hermaphrodites, 

 and become the mature parasites of the beetle, though how they 

 enter the body of the host is unknown. 



FIG. 74. Allantonema 

 mirabile Leuck. (From 

 Leuckart.) A, Male 

 Rhabditis stage, sexu- 

 ally mature, x 100 ; 

 B, the mature female 

 parasitic form, x 17, 

 showing at the upper 

 end part of the cap- 

 sule richly supplied 

 with the tracheae of 

 the host, a beetle ; C, 

 female Rhabditis stage, 

 sexually mature, x 

 100 ; D, the larva de- 

 veloped from the 

 Rhabditis form, x 

 102. 



The phenomenon presented by the hermaphroditism of Brady- 

 nema is, as far as we know, at present unique, as, though some 

 other Nematodes are hermaphrodite, in their case the her- 

 maphrodite form alternates with a bisexual generation. It is 

 further interesting as showing a means by which hermaphro- 

 ditism may arise, by the suppression of the females and the 

 assumption of their functions by the male. In the case of 

 Rhdbdonema nigrovenosum, no females appear in the alternate 

 generation. 



