22 -^I't 2. — T. Kaburaki ; 



Colouration. — The colour of the dorsal surface is usually 

 blackish or dark olive-like brown, especially dark in the median 

 parts. Small individuals, in which the pigments are not greatly 

 developed, may reveal the guts more or less distinctb/ in various 

 colours. The ventral surface is of a much paler colour than the 

 dorsal. 



Eyes. — The two eyes, each lying in a half-moon-shaped 

 colourless spot, are of a crescentic form. The distance between 

 them is equal to about one-fourth their distance from the frontal 

 margin, and somewhat less than the distance of either eye from 

 the lateral margin of the same side. 



The eye consists of a pigment cup and some visual cells. The 

 pigment cup is of an ovoidal shape with its opening at the side 

 and is, as usual, formed of very minute closely packed granules, 

 of a dark brown colour. Enclosed in the cup are visual cells which 

 are three in number. Each cell presents a fibrillous structure and 

 contains a large nucleus in the proximal part. 



Body Wall. — The epidermis, resting upon a fine basement 

 membrane, is not of the same thickness all over the body, being 

 very much thicker on the dorsal than on the ventral surface, and 

 being richly ciliated on the ventral surface. Numerous rhabdites 

 are found in the epidermis, which is perforated by the ducts of 

 rhabdite-forming cells scattered in sparse numbers in the paren- 

 chyma. The epidermic cells, each of a columnar shape, contain 

 an oval or rounded nucleus near the base, the protoplasm being 

 characterised by fine striations which are most prominent at the 

 basal parts of the cells. The dermal musculature consists of three 

 layers of circular, transverse and longitudinal muscular fibres. 

 The circular fibres he immediately beneath the basement mem- 

 brane, and form but a very thin layer. The thick longitudinal 

 layer is composed of a series of muscular bands, being rather more 

 strongly developed on the ventral than on the dorsal surface, 

 doubtless in ralation to the movements. In the parenchyma there 

 exist numerous glandular cells, which open out subm.arginally on 

 the ventral surface as well as at various points of the entire surface 

 of the body. A large accumulation of cells exists at both ends of 



