INVEKTEBRATA, CRYPTOGAMIA, MICROSCOPY, ETC. 267 



Encysted Scolex of Tetrarhynchus.* — Dr. Hoek describes the 

 characters of the Tasnioid cysts found by him in the connective 

 tissue of the mesentery and in the intestinal wall of a codfish. He 

 finds that the descrii^tion given by Van Beneden of the proboscis is 

 very exact, and he was able to observe in the living example its intro- 

 and eversion. When protruded the hooks with which it is provided 

 were seen to vary greatly in form ; except in the inferior region they 

 are set in whorls, and of these whorls there are some hundred and 

 fifty ; in the inferior portion the hooks are long, delicate, and curved ; 

 they may become hooked, broadened, and flatter, or they may take on 

 very remarkable forms. There are four chief water-vessels, but no 

 indication of a vesicle was to be made out, and transverse commis- 

 sures only exist in the region of the head ; in the suckers there is a 

 beautiful system of anastomosing vessels. The water-vessels open by 

 pores on the anterior side of the head, and on the anterior lateral 

 margins of the suckers. 



On the interesting question of the nervous system, the author 

 reminds his readers that Wagoner in 1857 announced the presence of 

 a large central cephalic ganglion with efferent nerves ; but those 

 observations have never been confirmed. What the author found 

 was this — throughout the whole body there extend several longitu- 

 dinal trunks, of which two on each side are the more distinct. They 

 have no connection with one another, are placed directly below the 

 integument, and give off small brandies, which pass into the reticular 

 connective tissue, and, if they are longitudinal trunks, innervate the 

 water-vessels and the sheath of the proboscis. These structures 

 liavc been followed into the head, whence their branches may be 

 followed out to the margin of the head, to the suckers, and so on. 

 As the author points out, they may be comparable to the spongy 

 lateral cords of Stcudinger, which seem to differ from them by forming 

 an anastomosis in the head. 



Dealing with the details of their histology, the author states that 

 the wall of the cyst is a smooth structureless investment of consider- 

 able thickness, and composed of several easily separable layers. The 

 only sjiccial point of histological structure appears to be the radial 

 bauds found in it. The worm itself can only be properly examined 

 by means of transverse sections; thus seen it exhibits from without 

 inwards a cuticle, a matrix from which the cuticle is developed, a 

 layer of longitudinal and a layer of transverse muscles, and an 

 cxtronicly fine connective tissue, the so-called parenchyma. To see 

 this last well it is necessary to remove the calcareous concretions. 



The scolex, like the cystic worm, is provided with a cuticle, 

 but it has ai)pended to it delicate hair-like processes, which are not 

 true cilia ; no pore-canals could bo seen. There is again a matrix, 

 tlie cells of the contained connective tissue vary greatly in size ; the 

 supposed nerve-trunks are made up of elongated elementary parts, 

 which are so far like ganglion cells that at one or both sides they are 

 continued into processes ; the efferent ramules are pale and finely 

 granulated, !So far as their structure is concerned, the author is 



* •Niedtrl. Aich. Zuol.,' v. (IST'J) p. 1 (1 phvlc). 



