458 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Structure of the Cestoda, and especially of Tetrabothriidse 

 and Tetrarhynchidse.* — Herr Theodor Pintner comes to the following 

 conclusions with regard to the water-vascular system : — It consists of 

 numerous ciliated infundibular cells, which are found in the whole of 

 the body, but are chiefly collected into a zone which lies between the 

 epithelium and the parenchyma, and which are provided with very 

 long capillary efferent ducts ; each of them is to be considered as a 

 unicellular gland. The substances collected into these funnels are 

 carried into a system of vessels which extends throughout the whole 

 length of the body, and which opens into a terminal contractile 

 vesicle ; the matrix of the walls of these vessels is a well-developed 

 epithelium containing a number of yellowish drops, insoluble in 

 alcohol. The type from which these longitudinal vessels may be 

 derived is jiresented by a simjile loop, formed of a dorsal and a 

 ventral branch, which extends to the anterior margin of the head, and, 

 by its tendency to form anastomoses, gives rise in various species to a 

 series of comj^licated arrangements. In all the Taeniadee, Tetra- 

 bothriidge, and Tetrarhynchidse there are on each side of the body 

 two longitudinal trunks, while in the Bothriocephalida3, Caryojihil- 

 lidea, and Ligulida these four trunks break uj) into from ten to 

 twenty-four longitudinal trunks, which are connected with one 

 another by transverse anastomoses. In an early stage the four 

 vessels are of much the same size, and all open into the terminal 

 vesicle ; later on, the two ventral enlarge at the expense of the two 

 dorsal vessels ; so that in all the free joints, or in very long chains, 

 the latter appear to be atroiDhied. In addition to their communication 

 with the exterior by means of the terminal vesicle, the vessels open at 

 the hinder margins of the joints ; in Trkenopliorus nodulosus alone 

 there are special orifices on the head and neck. Cfecal or ramifying 

 processes are never developed on the vessels, and they have no com- 

 munications with the lacunae in the tissue of the body. 



The author would agree with Hatschek in ascribing the closed 

 condition of the ciliated infundibula in the Platyhelminthes to the 

 absence in them of any body-cavity. 



In describing the structure of the head in Tetrarhynchus longicolUs, 

 the author points out that the two sucking-disks on it are really 

 formed by the fusion of two on either side. The remarkable flattening 

 of the head in this species makes its '* orientation " a somewhat diffi- 

 cult matter ; consideration, however, of the facts that the water- 

 vessels and nerve-branches are found to the right and left of it, and 

 not on the ventral or dorsal surface, leads the author to think that 

 the plane of flattening is perpendicular to the plane along which it 

 ordinarily takes place in Cestodes ; while the head is not bilaterally 

 symmetrical, but bi-radial, although the proof of this is obscured 

 by the difference in the size of the branches of the two water- 

 vessels. 



After describing in detail the structure and musculature of the 

 proboscis, Herr Pintner comes to histological characters ; it is not in 

 Tetrarhynchus only, but in all Cestodes that he has failed, notwith- 

 * Clans' Arbeiten, iii. (18S0) pp. 163-242 (5 pis.). 



