196 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.50. 



tapers only slightly toward the anterior end and attenuates abruptly 

 behind the anus to form the conical tail (fig. 253). The shape and 

 appearance of the anterior extremity is similar to that of the adult 

 worm. The tail often terminates in two papillalike projections 

 of variable size. Occasionally there are three, or there may be a 

 wing-shaped prominence with fringed or serrate edges. The 

 pharynx is relatively longer than in the adult worm and has rela- 

 tively thicker chitinous lining. The esophagus is about as long as 

 the intestine, or even somewhat shorter, and has the two-part struc- 

 ture of the adult worm. For a time the anterior portion of the body 

 and the esophagus grow faster than the posterior portion and the 

 intestine. Later the growth rates are reversed. The nerve ring is 

 distinct and the excretory pore is halfway between the nerve ring 

 and the union of the two portions of the esophagus. The primor- 

 dium of the genitalia appears as a small egg-shaped body, consist- 

 ing of a number of cells or a syncytium with several nuclei, located 

 near the region where the vulva will later develop in the female. 



When cockroaches containing encysted larvae are fed to primary 

 host animals, all of which are rodents, the larvae will be found to 

 have entered the mucous membrane on the following day. They 

 invade the mucosa of the stomach and not infrequently that of the 

 esophagus and tongue. In the next 10 days they grow slowly and 

 only double their length. Then they grow more rapidly and in a 

 few weeks are ten times as long as an encysted larva. At the end of 

 the first 10 days the larva has a tail identical with that of the adult. 

 About this time a molt occurs and the resultant larva has a simple 

 tail. After tAvo months females begin to pass eggs. 



In rodents these worms set up marked pathological alterations. 

 These begin as a circumscribed or diffuse hypertrophy^ of the mucosa, 

 go on to the formation of papilloma, and terminate in carcinoma 

 with occasional metastases. 



Hosts. — Epirnys norvogicus {Miis dccumanus), Epirnys rattus 

 {Mus rattus), Mus muscidus, O^'yctolagus cuniculus (Lepus cunicu- 

 7ns), Cavia porcellus {Cavia cohaya). 



Location. — The squamous-celled anterior porti(m of the digestive 

 tract. 



Localities. — Denmark, Danish West Indies. 



This worm is of very considerable interest from zoological and 

 medical standpoints. 



It is quite possible that Seurat (lOllc) has described this species 

 from Dipodillus campestris under the name of GongyloncTna hrevis- 

 piculum, a possibility which is commented on at length in the follow- 

 ing notes on that species. 



