408 



GENERAL ZOOLOGY 



CLASS II. NEMATOMORPHA. Hairworms. In the adult 

 state they resemble thick horsehairs. The integument consists 

 of a thick cuticula, beneath which is a single layer of epidermal 

 cells (hypodermis). The mouth and esophagus are closed in the 

 adult state in some species. The body cavity is lined with a 

 peritoneum and is provided with dorsal and ventral mesen- 



Fig. 236. Fig. 237. 



Fig. 236. — Ascaris lumbricoides. {After Beneden.) A, male three-fourths 

 natural size; B, female, three-fourths natural size; c, head, enlarged, ventral side 

 showing excretory pore; d, head, front view, three lobes surrounding the mouth; 

 e, posterior end of the body of male greatly enlarged showing penial setae. 



Fig. 237. — Acanthocephalid, male. (After Leuckart.) b, bursa; g, cement 

 glands; l, lemnisci, two saccular organs of unknown function; li, ligament; n, 

 nerve ganglion; p, proboscis and sheath; pe, penis; t, testes. 



teries. A pair of eyes and a number of tactile bristles are pres- 

 ent. The animals are dioecious and the fertilized eggs are 

 deposited in the water, where the larvae develop and later 

 parasitize aquatic insect larvae. If the host is eaten by a 

 predaceous insect, or if the host dies, the larva may enter the 

 body of a grasshopper or other insect. In either case, develop- 

 ment is completed in the second host, from which the adult 

 escapes through the body wall and eventually reaches water. 



