184.9.] 231 



situated about twenty-four rings above the anal aperture, which latter is placed 

 between the last two annuli of the body. Ovary double ; ova l-333d in. long, by 

 1-400 in. broad. 



Length of body from 1-13 to 1-llth inch ; breadth at commencement of vcntri- 

 culus l-118th inch ; at middle of body l-97th inch. Tail from 1-16 to l-15th inch 

 long, by 1-888 in. broad at its middle. 



2nd stib-gniHs, — TheJastoma.* 



Body cylindrical, attenuated anteriorly, strongly marked with moderately 

 broad annuli. Mouth small, opening at the extremity of a small papilla. (Eso- 

 phagus divided into two distinct portions, the first long and cylindrical, the second 

 constituting the true cesophageal bulb. Tail more than half the length of the 

 body. 



Tkelastoma attenuatum. — Female. Body attenuated anteriorly to commence- 

 ment of the ventiiculus, opalescent white, divided into from 140 to 160 annnla- 

 tions, of which there are from fifty-two to fifty-seven from the mouth to the com- 

 mencement of the ventriculus. Tail very straight, or very slightly curved or 

 bent, slender, inflexible and brittle, and sharply pointed. Mouth always pro- 

 jected, small, surmounting a small papillary elevation formed by the first annul us 

 of the body. Pharynx very short and narrow ; cesophagus strongly muscular, 

 cylindrical, l-47th in. long, by l-533d in. broad; cesophageal bulb pyriform, 

 l-17Sth in. long, l-222d in. broad. Ventriculus dilated alaeform at com- 

 mencement, cylindrical throughout. Rectum short, pyriform. Generative aper- 

 ture 42 annulations above the anal. Ovary double, ova l-333d in. long, by 

 l-400th in. broad. 



Length of body from 1-lOth to l-8th in. ; breadth at middle l-95th in. Tail 

 l-14th in. long, by 1-lllth in. broad at middle. 



Habitat, and Remarks. — Streptostoma agile and Thelastoma attenuatum are 

 found together principally in the commencement of the large intestine of Julus 

 marginatus, in numbers of from one to fifteen, and less frequently in the small 

 intestine with Ascaris infecta, in numbers of from one to six. It is remarkable, 

 that although I have found from one to fifteen of these two genera, in nine-tenths 

 of the animals examined, I have never yet been able to detect a single male. 



Thelastoma always has the mouth projected, whilst Streptostoma has it retracted, 

 producing, in some measure, but by no means wholly, the difference in size of 

 the oral aperture. 



At first I was inclined to think these two animals were difl'erent stages of the 

 same species, but the adults uniformly correspond to the descriptions given, and 

 in all cases contained more or less perfected ova. 



Their movements are active, wriggling the body in a sigmoid manner and 

 vibrating the delicate spiculated tail, which in sun-light resembles a shining 

 acicular crystal. 



Thelastoma, from its form of oesophagus and narrower annulations and shorter 

 tail than Streptostoma, occupies a position between the latter and Oxyuris. 



Gregari?ia Dufour. 



Body consisting of two distinct cells. Inferior cell the larger, marked 



* QtjXT} et otofia' 



