POLYCLAD FLATWORMS — ^HTMAN 73 



occur between the basement membrane of the epidermis and the sub- 

 epidermal musculature or, in short, the epidermis is elevated into a 

 hillock, thinned at the summit, by each tubercle. The tubercle con- 

 sists of an amorphous fibrous material with a number of nuclei; in 

 the present species its periphery is filled with dark pigm.ent granules. 

 Both the dorsal and ventral musculature, especially the latter, are 

 strongly developed in Ommatoplana. The tubercles lie directly upon 

 the dorsal subepidermal musculature, which probably has some 

 relation to the tubercles, but I was not able to see any strands of tissue 

 extending from the interior of the tubercles through the muscle 

 layer to the parenchyma, as described by Laidlaw (1903b). The 

 muscle layers of the ventral musculature do not seem to correspond in 

 the present species with those described by Laidlaw for tuberculata, 

 but it is not clear that the arrangement of the muscle layers is of 

 taxonomic significance. Under the thick basement membrane of 

 the ventral epidermis is a thin layer of circular muscles, followed by 

 a heavy longitudinal layer. This is followed by two layers of diagonal 

 muscles at right angles to each other and, finally, the innermost layer 

 is again a thick stratum of longitudinal fibers. However, I have only 

 longitudinal sections available, and possibly transverse sections would 

 reveal further details. 



CopuLATORY apparatus: All parts of the apparatus were found but, 

 as a fold is present at the site of the apparatus making it impossible 

 to obtain sagittal sections, the spatial relations of parts is difiicult 

 to ascertain. Figure 3,6 is therefore to be regarded as pieced together 

 from sections that cut the apparatus diagonally. The copulatory 

 apparatus is plainly that of a member of the Stylochidae. The 

 apparatus lies at the posterior end of the pharynx with the male 

 apparatus, in fact, beneath the last pharyngeal folds; however, the 

 spatial relation to the mouth was not clear. The sperm ducts, coming 

 from in front, acquire muscular walls, becoming spermiducal bulbs. 

 These unite with the seminal vesicle, forming a tripartite structure; 

 all three parts are closely similar histologically and are provided with 

 a fairly thick wall of circular muscle fibers. The tubular median part, 

 which is the true seminal vesicle, continues posteriorly to the penis, 

 narrowing to an ejaculatory duct, and before reaching the penis 

 papilla it joins the prostatic duct from the prostatic vesicle. The latter 

 is an oval body with a thick muscular wall of fibers paralleling its ex- 

 ternal contour and a relatively small lumen lined by a wavy epithelium. 

 Prostatic glands are not in evidence. The prostatic duct, encircled 

 by circular muscle fibers, joins the ejaculatory duct and the common 

 duct extends through the penis papilla to its tip. The penis papilla 



338100—55 



