RESEARCHES IN HELMINTHOLOGY AND PARASITOLOGY. 21 



Tail very straight or very slightly curved or bent, slender, inflex- 

 ible and brittle, and sharph' pointed. Mouth always projected, 

 small, surmounting a small papillary elevation forn^ed by the first 

 annulus of the body. Pharynx very short and narrow ; oesophagus 

 strongly muscular, cylindrical, i-47th inch long, by i-533d inch 

 broad; oesophageal bulb pN^riform, i-iySth inch long, i-222d inch 

 broad. Ventriculus dilated alaeform, at commencement cylindrical 

 throughout. Rectum short, pyriform. Generative aperture 42 an- 

 nulations above the anal. Ovary double, ova i-333d inch long by 

 I -400th inch broad. 



Length of body from i-ioth to i-8th inch; breadth at middle i-95th 

 inch. Tail i-i4th inch long b}' i-iiith inch broad at middle. 



Habitat and Remarks. — Strcptostoma agile and Thelastoma attemi- 

 atum are found together principally in the commencement of the 

 large intestine of Julus ))iargi)iatHS, in numbers of from one to fif- 

 teen, and less frequenth' in the small intestine with Asearis 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 yel been able to detect a 

 single male. 



Thelastoma always has the mouth projected, whilst Streptostoma 

 has it retracted, producing, in some measure, but b}^ no means 

 wholly, the difference in size of the oral aperture. 



At first I was inclined to think that these two animals were dif- 

 ferent stages of the same species, but the adults uniformly corre- 

 spond 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 sunlight 

 resembles a shining acicular crystal. 



Thelastoma, from its form of oesophagus and narrower anuulations 

 and shorter tail than Streptostoma, occupies a position between the 

 latter and Oxynris. 



Greg a rin a, D u f o u r . 



Body con.si.sting of two distinct cells. Inferior cell the larger, 

 marked with delicate parallel, longitudinal lines, (muscular?) and 

 filled with a fine granular matter, obscuring one or two nucleolo- 

 nucleated organic cells. Superior cell placed in a depression of the 

 inferior, surmounted by a slight papilla in which may be detected 

 two lines, apparently outlines, of an oral canal to the interior of the 

 cell which is filled with granular matter ; cell wall amorphous and 

 transparent. 



