248 ANIMAL PARASITES AND MESSMATES. 



The ordinary crab of our coasts, Carcinus mmnas, is 

 the vehicle of a nematode which becomes a CoroniUa 

 robusta in the stomach of a ray. 



The Heteroiira androphora is another nematode which 

 lives in the stomach of tritons. The male is always 

 rolled round the body of its female. The two sexes are 

 always free, contrary to that which is observed in the 

 S3mgami. The Blattse, coleopterous insects, also harbour 

 sexual nematodes. Kadkewisch saw two species of an- 

 guillulae, the Anguillida 7nacrou7'a Siiid appendiculata, in 

 the Blatta orientalis, and an Oxyuris brachyura in the 

 Blatta germanica. These eggs leave the body with the 

 feces, and resist the action of deleterious agents. 



Ileterodera Shachti is the name given to a nematode 

 which Mons. Schacht discovered on beet-root. This is 

 also a dimorphous worm ; the male has the usual form, 

 the female resembles a lemon. The Leptodera appen- 

 diculata inhabits the foot of the Arion empiricorum, in 

 the larva state, and becomes sexual (male .and female) 

 in the decomposed body of the snail. The next genera- 

 tion has the sexes united, and lives in damp earth. The 

 Leptodera pellio lives in the same way in the bodies oi 

 lumbrici; another Leptodera inhabits the intestine of 

 the snail, and a third the salivary glands. The ne- 

 matode so generally known under the name of Ascaris 

 nigro-venosa also belongs to this genus. It lives in the 

 lungs of the frog. There is one also in the lungs of the 

 toad, but it differs from the preceding. 



Leuckart looks upon these worms as females, and 

 their reproduction as parthenogenetic. Schneider con- 

 siders that the male exists by the side of the female sex, 

 and that they are consequently hermaphrodites. These 



