170 



NEMATHELMINTHES 



THAI' 



of the Nematoda, and it must therefore be placed with it in the 

 Nematomorpha. 



On the other hand, it ought to be mentioned that Camerano 1 

 found that the chief details of the fertilisation and development 

 of the egg in Gordius closely conform with what is known of the 

 same processes in Nematodes, and he is of opinion that these 

 resemblances are sufficiently important to justify the retention of 

 the group among the Nematoda. 



Life -History. The life -history of Gordius comprises four 

 stages the early development of the egg, the first larval form, 

 the second larval form, and the sexually mature form. Both 

 larval forms are parasitic, and during their life they are actively 

 engaged in feeding ; the free form, on the other hand, takes in no 

 nourishment, and is exclusively engaged in reproduction. 



Von Linstow 2 gives the following account of the life-history 

 of G. tolosanus, a form which has been more 

 fully worked out than any other. In the 

 month of April numerous specimens of the 

 beetle Pterostichus niger were found float- 

 ing on the surface of the ditches and 

 small ponds in the fields surrounding 

 Gottingen. Some were found dead or dying ; 

 others appeared quite healthy, and these 

 were swimming actively, endeavouring to 

 reach land. Within the abdomen of these 

 beetles, in about 20 per cent of those 

 collected, the second larval form of the G. 

 tolosanus was found. The longest larvae 

 were 122 mm. in length, and very soft, 

 partly snow-white and partly brown in 

 the Gordius larva within, colour ; traces of the boring apparatus of 

 (From von Linstow!) * ' tne fi rs t larval form were still to be seen, 

 but in other respects the larva only 

 differed from the free form in the immaturity of its sexual organs. 

 Besides the parasite hardly anything was to be found in the 

 abdomen of the beetle, the larva having eaten up all trace of the 

 fat body and the generative organs of its host. The larvae bored 

 their way out of the body of the beetle and became adult animals. 

 It is rather difficult to say what brings these essentially 



1 Mem. Ace. Torino, 2nd ser. vol. xl. 1890, p. 1. 2 Centrlb. BaTcter. Bd. ix. 1891, p. 760. 



Fig. 88. Abdomen of Ptero 

 stichus niger with th< 

 terga removed to expose 



