86 Mr. H. A, Bay lis on a 



balsam. Tlie various series of sections that liave been cut 

 have proved useful mainly in confirming conclusions at 

 wliich I had previously arrived from the examination of the 

 whole preparations. 



Ileterorchis cnmienifer, gen. et sp. n.* 

 External Features. 



The contour of the animal, as seen from above or below, is 

 oval, tapering slightly towards either end. Anteriorly the 

 body is flattened, but posteriorly the ventral side is much 

 swollen by the development of the uterus, so that the body 

 is more cylindrical in this region. The total length of the 

 animal (without pressure) is about 3 mm., and its maximum 

 width, under the same conditions, 1 mm. 



The exterior of the body is armed with small, flattened 

 scales, semicircular in outline ; they occur on the oral and 

 ventral suckers and on the anterior part of the body, both 

 dorsally and ventrally, extending backwards for a short 

 distance behind the ventral sucker. Somewhat larger scales 

 also occur along the sides of the body for about three-quarters 

 of its length. The posterior end of the body is without 

 scales, and in some of the older individuals many of the 

 scales on the more anterior parts appear to have fallen off, 

 leaving almost the entire body smooth. 



Tiie oral sucker measures 0*38 to 0*46 mm. in diameter, 

 and has a small opening. The ventral sucker is larger, 

 liaving a diameter of 0"55-0"72 mm., and has a wide aperture. 

 On an average, obtained from the measurements of nine 

 individuals, the ratio of the diameter of the oral to that of the 

 ventral sucker is nearly as 2:3. The ventral sucker is 

 situated almost entirely within the anterior third of the body, 

 its distance from the oral sucker being only about 0'4 mm. 



The genital aperture is situated anteriorly and ventrally, 

 almost on the extreme left side of the body ; it is about equi- 

 distant from the oral and ventral suckers. The cirrus is 

 sometimes seen protruded from the aperture. 



On the dorsal side of the body there is a structure wliich 

 is the most remarkable feature of the species. At a short 

 distance from the posterior end there is a very large circular 

 or transversely elliptical aperture, extending sometimes 

 almost completely across the body from side to side, in speci- 

 mens which have not been flattened by pressure. This 

 opening leads forward into a spacious sac or pouch. The 



* A generic diagnosis is given on p. 95. 



