292 F. F. LAIDLAW. 



The body is characterized by its tenuity, its average thickness is only from '3 to '4 mm. 

 Along the middle line there is of course a considerable thickening over the pharynx and 

 genital apparatus, forming a ridge such as usually occurs in a Polyclad. 



On the dorsal surface the epidermis contains large numbers of rhabdites about '01 mm. in 

 length. These are absent from the ventral surface. In addition to the rhabdites, pseudo- 

 rhabdites occur numerously in both the dorsal and ventral epidermis. They are pellet-like 

 bodies composed of a coarsely granular material, and are rather longer and at the same time 

 thicker than the rhabdites. They are of sufficient size and number to give the whole surface 

 of the body a granular appearance when viewed with a simple lens. On the dorsal surface of 

 the tentacles the character of the epithelium differs markedly from that found elsewhere (see 

 fig. 17). No rhabdites and only a very few small pseudorhabdites occur, and the whole ejjithelium 

 has a very regular columnar arrangement, the nuclei all lie at the same level, viz. at about 

 the middle of the cell. The cilia are not modified in any way, nor does there appear to be 

 any special sensory apparatus. On the ventral surface of the tentacles the arrangement of 

 the epidermal nuclei is quite irregular, and pseudorhabdites are fairly numerous, though not 

 so abundant as over the general surface of the body. 



The basal membrane lying below the epidermis is moderately thick; immediately below 

 it lies the pigment, which to a great extent obscures the dorsal musculature. On the tentacles 

 the pigment presents the appearance of being contained in chromatophores, whilst over the 

 general dorsal surface of the body it is more diffuse and may be intercellular. In the 

 flattened lateral parts of the body the inner longitudinal ventral muscle-layer is very 

 strongly developed and extends dorsalwards for fully one-half of the thickness of the body. 

 The muscles are but feebly developed in the tentacles; the space lying below the body- wall 

 is almost entirely occupied with nerve-tissue. The " sucker " has its disc covered with a non- 

 ciliated columnar epithelium ; the nuclei are scarcely distinguishable, and the basal membrane 

 very thin. Amongst the muscles below the basal membrane lie elongated gland-cells, full of 

 a finely-granular secretion. Processes from these cells pierce the basal membrane and make 

 their way through the epithelium to the surface. No pseudorhabdites are found in the epi- 

 thelium of the disc. The pharynx is much folded and of considerable size, resembling in its 

 arrangement that of Anonymus viridis. 



Genital apparatus. In the two specimens from which sections were prepared the genital 

 apparatus was well developed (Fig. 65). The vagina (va.) is of the type usually found in 

 the Cotylea; that is to say, it runs upwards from the gonopore ($), dilating at the point where 

 it receives the shell-gland secretion {sh. gl.), further on narrowing again. It then turns back 

 and downwards for a short distance, finally terminating in the uteri (ut). 



It is in connection with the uteri themselves that some of the most interesting characters 

 of this species occur. In the first place there are a number of small rounded vesicles (ut. v.) 

 each connected with the uteri by a short stalk-like duct. These vesicles in some cases 

 contain quantities of spermatozoa, suiTounding what appear to be fragments of eggs (cf. Wood- 

 worth [20], p. 66). In addition at intervals along the uteri are gaps in the walls, through 

 which project into the lumen of the uteri cells, bearing a close resemblance to the yolk-cells 

 of Dendrocoelum lacteum figured by Ijima [8] (see especially PI. XXI. figs. 7-10, loc. cit.). This 

 character is of importance, as hitherto no Polyclad possessing any organs comparable to the 

 Triclad yolk-glands had been described. 



