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



breadth, while the pharyngeal sac and the pharynx are contained within the second 

 body fifth. In specimen (6) the pharynx is longer and more cylindrical. In both 

 specimens the lumen of the pharynx is dilated just in front of its oblique opening into 

 the gut. 



The main gut is spacious and extends to near the posterior end of the body, giving 

 off five lateral roots on either side and a median anterior root. All the roots branch 

 freely without apparently anastomosing. The main gut opens to the external surface 

 by a ciliated pore in the mid-dorsal line near the commencement of the last body fifth 

 in specimen (a), and rather further forward in specimen (b). 



Brain. The brain is large and lies close in front of the wall of the pharyngeal sac. 

 With the anterior gut root it occupies the entire depth of the interior of the body in the 

 middle line. 



Eyes. Immediately beneath the basement membrane and overlying the brain are 

 two groups of eyespots each containing about fifteen ocelli. These groups are separated 

 from one another by the anterior gut root. Deeply sunk in the parenchyma, on the 

 outer anterior surface of the brain on either side, is a single ocellus similar to that 

 described by LANG in Aceros inconspicuus (l); there are also eight to nine eyespots 

 scattered along the anterior body margin on either side of the middle line. These may 

 be described as tentacular eyes, though actual tentacles are absent from this as from the 

 other species of Aceros. 



Genital Organs. The male aperture lies immediately behind the mouth in specimen 

 (a), while in specimen (b), owing apparently to differences in muscular contraction, it 

 might almost be described as having a common opening with the mouth. 



The male organs consist of penis, " granule gland," seminal vesicle, vasa deferentia, 

 and testes. 



The penis is large, of an elongated, pyriform shape, almost equal in length to the 

 retracted pharynx in specimen (a), but slightly shorter in specimen (b). The lumen of 

 the penis is dilated posteriorly, and is lined by a single layer of greatly elongated 

 cells. Its relatively thin muscular wall forms a uniform sheet round the dilated 

 part of the lumen and tapers off gradually towards the apex. The lumen of the penis 

 is connected posteriorly by an extremely fine passage with the large " granule gland " 

 (prostatic vesicle). This passage receives from behind the minute canal from the 

 seminal vesicle. The " granule gland " vesicle is lined by a single layer of cubical, non- 

 ciliated epithelium covered by a thin muscular wall. The seminal vesicle has a strong 

 muscular wall and is filled in both specimens with spermatozoa. It lies behind the 

 " granule gland " and below the gut, and ends in a pair of vasa deferentia which by 

 rapid and repeated branching come into connection with the small and very numerous 

 lobules of the testis. These lobules are scattered throughout the lateral parts of the 

 body in the septa between the gut branches, ventral to the ovarian tubes. 



The female apparatus consists of aperture, shell-gland portion, duct of uterus, 

 uterus, oviducts, and ovarian tubes. 



(ROY. soc. EDIN. TRANS., VOL. XLV., 820.) 



