American Representatives of Distomum variegatum. 909 



serving the worm, I thouglit I liad D. cylindraceum, a species which 

 I liave never yet found represeiited in any of our amphibia. 



In form this worm appears long and narrow, broadest near the 

 posterior end wliicli is rounded and lieavy, but tapering gradually 

 towards the anterior end which is usually thin. »Sections show the 

 greatest depth in the region of the ovary, where the vertical and 

 transverse diameters are to each other as 2:3. My longest moimted 

 preparation measures 11 mm by 1*25 mm. Living ones may reach 

 15 or 16 mm in length. 



The ventral sucker is very small and difficult to see but may 

 be found in alcoholic specimens by a lens. It is situated a little 

 more tlian one third from the anterior end and is less than one-half 

 the diameter of the oral sucker. In a worm 9 mm long it measured 

 •12 mm across as compared with 'Sl mm for the mouth-sucker and 

 was 3-33 from the anterior end. Sections of a worm but slightly 

 shorter than this show the sucker to be '062 mm in depth. 



The cuticle is only half as thick as in the preceding species; 

 its spines are similar in shape but only half as long, very thin and 

 at least four times as numerous, so that, under a high objective 

 and low ocular, they appear very much like a dense coat of short liair. 



The ovary is generally round or oval, but sometimes distinctly 

 lengthened and, in a few cases, with two or three shallow in- 

 dentations on the outer side and short, rounded lobes between them. 

 As in the preceding species the number of cases in wich it is 

 situated on the right side seems to be slightly the greater. In 19, 

 examined at the one time, 12 were on the right. It is a little 

 farther separated from the ventral sucker than is usual in this 

 group of forms and has the large receptaculum seminis immediately 

 behind it, but more in the centre. 



The festes are at a greater distance from the ovary than is 

 usual. Sometimes they are perfectly round in appearance but at 

 other times they are slightly lengthened and, in one preparation 

 I have, they show slight lobings, which may, however, be due to 

 contraction. Their arrangement, right or left, depends rigidly upon 

 he Position of the ovary — the one nearest the ovary being on 

 the other side, that farthest away on the same side. 



The vitellaria have the usual position and arrangement of ten 

 to twenty large follicles in a group. 



The most characteristic part of the Uterus is that behind the 

 last testis ; the descending limb forms folds, loops, or coils do\Vn one 



58* 



