1 84 NEMATHELMINTHES CHAP. 



Hamann places three species in this family : Gigantorhynchus 

 echinodiscus, G. spira, and G. taenioides ; but as he points out 

 that E. gigas resembles these in its more important structural 

 features, it seems advisable to include it here under the name 

 G. gigas. The members of the first family often present a trans- 

 versely ringed appearance after death, but the Gigantorhynchidae 

 are ringed when alive, and the circular canals in the skin show 

 a certain regularity, being arranged one between each two rings. 

 There is no lumen in the proboscis-sheath, which is not attached 

 to the boundary between the proboscis and the trunk, but to the 

 inner surface of the proboscis, and the whole can be retracted 

 within the anterior portion of the body, which is invaginable. 

 There are always eight cement-glands, and other differences exist 

 in the musculature, hooks, and position of the nervous system. 



G. gigas occurs in the adult state in the small intestine 

 of swine ; in Europe its first or larval host is believed to be the 

 grubs of Melolontha vulgaris and Cetonia aurata, but these beetles 

 are absent from America, though the parasite infests American 

 hogs. Stiles * has recently made some experiments which tend 

 to show that in the United States the source of infection is some 

 species of the beetle Lachnosterna, and he has succeeded in in- 

 fecting the grub of L. arcuata by feeding it on the eggs of the 

 parasite; from one larva he took 300 parasites six weeks after 

 feeding it. L. arcuata is, like M. vulgaris, phytophagous, but 

 the grubs of both the beetles are fond of frequenting manure 

 heaps and patches of dung, and thus are much exposed to the 

 dangers of infection. 



G. echinodiscus inhabits the intestine of ant-eaters, having 

 been found in Myrmecophaga jubata and Cycloturus didactylus. 

 G. spira lives in the king vulture Sarcorhampus papa, and G. 

 taenioides in Dicholophus cristatus, a species of Cariama. 



Family HI. Neorhynchidae. Sexual maturity is reached in 

 the larval stage. The proboscis-sheath has a single wall. A 

 few giant nuclei only are found in the sub-cuticle ana in the 

 lemnisci. The circular muscle layer is very simply developed. 

 The longitudinal muscle-cells are only present in certain places. 



This family includes two species, Neorkynclms clavaeceps and 

 N. agilis, which afford interesting examples of paedogenesis. 

 The sub-cuticle and the lemnisci are dominated by a few giant 

 1 Zool. Anz. vol. xv. 1892, p. 52. 



