716 MR. F. F. LAIDLAW ON THE POLYCLAD [June 19, 



of some 20 eye-spots (see text-%. 113, p. 715). Almost at the 

 extreme anterior extremity there projects outwards on either side 

 a fine tentacle-like process devoid of eye-spots, and evidently very 

 contractile, varying much in length in the difierent individuals 

 preserved. 



The brain (6r.) lies about half a millimetre behind the anterior 

 extremity, over it lie a few eye-spots. The pharynx opening is 

 near the middle of the ventral surface ; the pharynx is rather 

 elongate and convoluted. The genital apertures lie close together 

 in the rniddle line, the female behind the male, about a millimetre 

 and a half behind the pharyngeal ape]?ture. At the extreme hinder 

 extremity of the ventral surface is a sucker-like organ (c). 



The cells forming the epidermis are rather flattened and show 

 no i-habdites ; some of them contain irregidar thread-like 

 secretions. The cells at the margin of the body are more 

 columnar than those on the dorsal or ventral surfaces. The 

 ventral cilia are three times as long as the dorsal. 



The muscles of the body- wall consist of an outer, longitudinal 

 layer, and of an inner, circular layer, both feebly developed : on 

 the ventral side there is a second longitudinal layer internal to 

 the circular fibi'es, well developed, and occupying neai'ly one- 

 fourth of the total thickness of the body. 



Gut. — The main-gut extends from just behind the brain to the 

 hinder end of the body, and gives off numerous lateral branches ; a 

 branch also passes forward over the brain. 



Structurally the branches are distinguished from the main-gut 

 by the fact that in them the large gland-cells, which, from their 

 deep staining, are very conspicuous, are scarce or as a rule absent, 

 whilst in the main-gut they are very abundant. 



Genital apparatus. — The testes and ovaries both lie dorsal to 

 the gut-branches, though sometimes the ovaries extend down 

 between them. In the specimen sectionised both testes and 

 ovaries are mature, and, as in other Polj^clads, very numerous. 



The contorted ends of the vasa deferentia run forwards and 

 inwards to open together into the base of the penis. This is a 

 conical organ which projects backwards into a small cavity, the 

 antrum masculinum. This organ is not muscular, but consists of 

 a spongy mass of tissue through which the duct runs to open at 

 its apex. The projecting part of the penis is lined with an 

 epithelium continuous with the lining of the antrum. This latter 

 opens into a small depression or cup on the ventral surface, and 

 on either side of it is the opening of a very remarkable duct 

 leading from a compound racemose gland of a type quite unlike 

 anything I have met with in other Polyclads. These ducts are 

 lined with columnar ciliated cells ; they run upwards and outwards 

 on either side of the penis in a transverse plane, and each 

 terminates by branching into a number of small chambers. These 

 are themselves lined with columnar epithelium of the same type 

 as the ducts, but that forming the roof of each chamber projects 

 more into the knnen of that chamber than does the epithelium of 



