152 



NEMATHELMINTHES 



A similar protandry exists in the parasitic forms of Allantonema, 1 

 of which there are several species A. mirabile in Hylobius pini, 

 A. sylvaticum in Geotrupes sylvatica, A. diployaster in Tomicus 

 typographies ; but in their case the male and female forms which 

 leave their host pair in the damp earth and give rise to larvae 



FIG. 75. Atractonema gibbosum Leuck. (From Leuckart.) 1, Female with commenc- 

 ing prolapsus of the uterus and neighbouring parts, x 130 ; 2, a further stage, the 

 female being now sexually mature, x 15 ; 3, a still older stage, with commencing 

 degeneration of the body of the female, x 15. 



which make their way into the body of the beetle-grubs. Here 

 they undergo very extensive retrogressive change. The body of the 

 female, which becomes the shape of a thick sausage, is encapsuled 

 and surrounded by a curious hypertrophied network of tracheae 

 (Fig. 74). As is usually the case with the degenerate parasitic 

 forms, there are practically no organs but the ovary, and this is 

 1 Kud. Leuckart, Alh. Sachs. Ges. vol. xiii. 1887, p. 567. 



