ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 459 



standing the greatest care, in detecting the pore-canals in the cuticle, 

 the presence of which has been so frequently asserted ; instead of 

 ducts he would speak rather of small hairs as investing the cuticle, 

 but he finds no sign of any ciliation. Below the " hairs " he finds a 

 thicker cuticle, then a delicate layer with transverse fibrillge, and 

 another below that with longitudinal fibrils ; and all these he believes 

 are, with rare exceptions, to be found in all the Cestoda. 



Under these, in Tetrarliynchus, there is in the head a special layer 

 made up of bundles of fine non-nucleated muscular fibrillje, which 

 give a diagonal-square pattern, even on the most superficial examina- 

 tion. Below this is an epithelial layer, in which there are some 

 indications of unicellular glands, and under this, and separating it 

 from the proper parenchyma of the body, there is a cellular layer of 

 a remarkable character ; consisting, as it does, of irregular membrane- 

 less cells of various sizes, and containing a homogeneous dirty plasma, 

 which gives off processes in all directions, which unite with those of 

 the neighbouring cells and form a tubular network investing the 

 whole body-parenchyma. These cells, which can only be rendered 

 distinct by treatment with osmic acid, have well-marked nuclei and 

 excentric nucleoli. The connected cells give rise to smaller or larger 

 canaliculi which communicate with one another and run in various 

 directions. 



This system would seem to have the following functions : some of 

 the cells further assimilate the nutriment taken in by the integument, 

 and pass it to the canaliculi of the plasmatic canal system, other cells 

 take up the innutritions material and convey it to the ciliated infundi- 

 bular cells of the excretory system, to be evacuated. 



As to the parenchyma, the author is largely in agreement with 

 V. Kennel's results on 3Ialacobdella ; in the most anterior part of the 

 head he finds a special compact tissue, consisting of a larger central 

 and of four smaller lateral portions ; pale red in colour and containing 

 doubly-contoured fibrillaa which call to mind elastic connective-tissue 

 fibres or the supporting fibres of the gelatinous tissue of the Medusre, 

 it has in its most central portion very pale cells with processes, which 

 resemble the mucous or gelatinous tissue of the higher animals. 



The muscular tissue is either transversely striated and without 

 nuclei ; or smooth and without nuclei ; or smooth with a nucleus in the 

 sheath ; or smooth, with nuclei ; or branched and flattened. As to the 

 nervous system, he finds that it consists of a flattened mass of ganglion- 

 cells which ends in a point posteriorly and is enclosed in a mem- 

 branous sheath, provided with nucleated muscular fibres. Two nerve- 

 trunks are found dorsally and ventrally to this cerebral mass, which is 

 placed between the sucking-disks. At the level of the brain these 

 dorsal and ventral trunks are connected by a transverse commissure ; 

 the trunks on either side unite, to be again separated further down, 

 and thus there is formed a nerve ring which surrounds the cerebral 

 mass. The two outer nerve-cords pass between the water-vessels 

 into the outer parenchyma, and give off at regular distances transverse 

 branches ; the two inner run in the inner parenchyma and supply the 

 proboscis, where they come into connection with some remarkable 



