134 DR J. F. GEMMILL AND DR R. T. LEIPER 



Brain. The brain lies in front of the mouth, at the junction of the first and second 

 body fifths. 



Sucker. The sucker, which is large and slightly elevated, lies a little in front of the 

 middle of the body. It rests on a pad of muscular tissue which is continued into the 

 walls of the posterior part of the pharyngeal sac. Here the tissue in question is 

 permeated by fine mucous canals which open into the sac. 



The older specimen (specimen a) is much injured dorsally, and has its pharynx 

 retracted to an extreme degree. Partly owing to the injury and partly to the 

 extremely hard nature of the tissues below the pharyngeal sac, a satisfactory series 

 of sections of this specimen was not obtained. This circumstance is all the more to 

 be regretted seeing that the smaller specimen, though it furnished a good series of 

 sections, was quite immature as regards the genital organs. 



Digestive System. The mouth lies in front of the brain and opposite the tentacles, 

 at one-sixth of the body length from the anterior body margin. The pharyngeal sac 

 is long and narrow, with a backward diverticulum above the position of the sucker. 

 In specimen (b) the pharynx, which is long, tubular, and tapering towards the apex, 

 lies fully extended within the pharyngeal sac. (Plate fig. 4.) In specimen (a) the 

 pharynx is completely retracted within the posterior part of its sac, the mouth leading 

 first into a slightly dilated part from which the sac is continued backwards as a narrow 

 canal to the posterior dilatation in which the pharynx lies. The cavity of the pharynx 

 opens into the gut a little behind the junction of the first and second thirds of body 

 length. 



The main gut is spacious, extending forward for a considerable distance in front of 

 the internal opening of the pharynx. The lateral gut roots are five in number on either 

 side, and some of their branches anastomose near the margin. The anterior gut root 

 extends forward over the middle part of the brain and divides without anastomosing 

 with any of the branches of the first lateral gut roots. 



Genital Organs in Specimen (a). The male opening lies close behind the mouth 

 and leads into a penis sheath cavity of considerable size. (It must be stated here that, 

 owing to the injured condition of the specimen, the succeeding part of this description 

 of the male organs may not be quite complete or accurate, and it is therefore liable to 

 correction should further specimens be obtained.) At the bottom of the penis sheath 

 cavity is a small conical elevation, above which is a muscular backward diverticulum 

 of the penis sheath cavity. (Plate fig. 5.) The elevation is perforated by a 

 fine passage which appears to be continuous with the central canal of an oval organ 

 lying close behind. The walls of this organ are so hard and dense as to show 

 practically no histological structure. Into the posterior end of its central cavity opens 

 a short canal formed by the union of the two vasa deferentia. These last are full of 

 spermatozoa and irregularly dilated, each exhibiting a very large swelling just before 

 its first main branch is given off. The lobules of the testis are numerous, large, and 

 scattered throughout the lateral parts of the body. 



(ROY. soc. EDIN. TRANS., VOL. XLV., 824.) 



