ENTOZOA 431 



lining of the former seems to be a structureless cuticle with no cells especially related to 

 it, but the wall of the dorsal vessel is surrounded by a number of small deeply stained 

 cells (fig. 4). I did not see any communication between the vessels of one side, but 

 the larger vessels communicate as usual, one with another, by a transverse vessel 

 running from side to side along the posterior border of each segment. In the head the 

 vessels all communicate. In some of the better preserved sections such structures as 

 are depicted in fig. 10 were seen : these may or may not be flame-cells ; they look 

 rather like them. No valves were seen in the course of the vessels. 



The lateral nerve-cords are well marked, lying externally to the ventral excretory 

 canals ; they fuse together in the head, forming a ganglion which is indicated in fio-. 3. 

 No traces of the nerve-ring described by Tower' as running round the posterior end of 

 each segment of Moniezia, or of the secondary nerves described by the same observer, 

 were to be seen. But these, if present, probably require fresh material and special 

 methods of preservation to make them manifest. Special nerve-cells, described below, 

 are scattered through the parenchyma of the body. 



The histology — at least in some specimens — could be fairly well made out, and 

 agrees roughly with what Blochmann has described in Ligtila monogramma' . The 

 whole body is covered by a cuticle, the outer fifth of which stains more deeply than the 

 remainder. Within this, with a high power, a number of dots or knobs become visible 

 (fig. 10). These are the swollen terminations of certain strands or processes of the 

 ectoderm cells. The cells themselves, as Blochmann has shown, lie removed to some 

 distance from the cuticle they secrete, but are in contact with it by means of the above- 

 mentioned processes ending in the knobs. 



The ectoderm cells are not all at one level, but on the whole form a fairly well- 

 marked layer. Each cell is fusiform in shape, and produced into two or three processes, 

 which project both peripherally and centrally. They contain large and well-marked 

 nuclei. Neither the cells nor their processes are laterally in contact ; they are separated 

 one from another to varying extents by the intrusion of some of the parenchymatous 

 network which makes up so much of the body of a Cestode. 



This parenchyma consists of a meshwork which permeates everywhere the body of 

 the tapeworm, surrounding all the organs, and often, as is the case with the ectoderm 

 and the muscles, passing in between their constituent cells. In the spaces of the mesh- 

 work there is believed to be a fluid. The meshwork itself is secreted and nourished by 

 certain large star-shaped cells which are irregularly scattered through the parenchyma, 

 and which give off processes in all directions (fig. 10). 



Round the generative glands this parenchymatous network becomes condensed, 

 the spaces disappear, and it forms a close sheath to the ovary, testis, &c. At the 

 posterior end of each segment it is also somewhat condensed, and in section presents 



' Zool. Anz. vol. XIX. 1896, p. 323. 



' Die Epithelfrage bei Cestoden und Trematoden, Hamburg, 1896. 



F. H. II. 56 



