634 WILLIAM A. HASWELL. 



and are so strongly coloured by the hsematoxylin^ that scarcely 

 any intermediate substance is distinguishable. It is in this 

 zone that the wide portions of the superficial unicellular glands 

 lie embedded. Here and there occurs a cell of stellate shape. 

 Below this zone is the inner circular layer of muscular fibres, 

 which is much thicker than the outer ; and below this again 

 is the inner longitudinal layer, which is of great thickness, 

 and extends uniformly over both surfaces. 



The deep integumentary glands lie below the muscular 

 layers, scattered through the parenchyma in all parts of the 

 body. Their ducts, which frequently branch and perhaps 

 anastomose, pass from them with a sinuous course, perforate 

 the muscular layers and the layers of the integument, and 

 open on the outer surface. Each gland consists of a single 

 cell of about •! mm. diameter^ of evenly rounded outline 

 without processes, except where the duct is given off". Enclos- 

 ing the cell is a distinct capsule, in which lies a flattened 

 nucleus as large as that of the cell itself. The nucleus of the 

 gland, situated towards the middle, always has a lobed outline, 

 and contains about six spherical nucleolar bodies of about equal 

 size. The cytoplasm exhibits a strongly marked reticulum, 

 the threads of which have a prevailingly radiate arrangement. 

 The interfibrillar substance appears clear and homogeneous in 

 the great majority of the glands, but in many the cell is full 

 of well-formed rhabdites. The ducts appear as tubes with 

 well-defined walls. When they enter the zone of ducts they 

 become dilated, contracting again as they pass through the 

 superficial layers. The ducts of the glands which contain 

 rhabdites also contain rhabdites, while in the interior of the 

 ducts of those glands in which no rhabdites occur is a reti- 

 culum similar to that of the cell itself. Special strands of 

 ducts of the deep integumentary glands run forwards to open 

 about the anterior margins of the body, and very many open 

 on the extreme lateral margin. The parenchyma completely 

 and closely fills up the interspaces between the organs, and a 

 coelom, such as is described as being characteristic of the 

 Rhabdocoeles in general, is not in any way represented. The 



