ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
431 
the anterior part of the body is male, the posterior female. One indi- 
vidual is chiefly male, possessing six distinct testes and three distinct 
ovaries, the other mainly female with a single well-marked anterior 
testis, and the remaining gonads female. Both ovaries and testes have 
usually the appearance of solid masses of protoplasm. 
Gyrodactylus.* — Dr. L. Kathariner gives an account of this ecto- 
parasitic Trematode, found on freshwater fishes. A general description 
is given of the form of the body, of its investment, and of the glands 
that are found on its surface. The muscular system is of the type 
common to most Trematodes. The central nervous system, on which 
earlier authors make no reports, lies in front of and above the pharynx. 
It forms a band which is slightly concave backwards, and its corners 
are produced into two cords which pass to the ventral surface, where 
they may be followed to about the middle of the body. From the 
anterior margin of the brain commissure there arise two nerve-trunks, 
which at first diverge from and then converge towards one another. In 
histological structure the substance of the brain and of the nerve-trunks 
appears to consist of very fine fibres which stain with difficulty. Among 
the fibres there appear a certain number of ganglionic cells. A detailed 
description is given of the digestive canal. The wall of the intestine 
appears to be devoid of muscles, but around the intestine there are 
numerous parenchymatous muscles, some of which pass to it radially 
from the dermomuscular tube, while some form circles around it ; this, 
of course, is not the first Trematode which has been shown to be devoid 
of an enteric musculature. In a living Gyrodactylus the excretory 
apparatus may be distinctly seen to consist of four longitudinal trunks. 
The two larger of these have their orifices in the anterior part of the 
body which is behind the pharynx, and they are provided with an 
enlargement which functions as a contractile vesicle. There are some 
difficulties in demonstrating the course of the vessels, as in preserved 
animals nothing can be seen of them. The animal under investigation 
is hermaphrodite, with well developed male and female organs, as Wagner 
was the first to show. These organs are described by the author in 
detail, and he adds critical remarks on the observations of his pre- 
decessors. Laurer’s canal is absent. After a few notes on the mode of 
life of this parasite the author concludes with enumerating the species 
of the genus. To the G. elegans first described he adds two new 
species which he calls G. medius and G. gracilis. 
Histology of Trematoda.t — Dr. A. Schuberg first discusses the 
peripheral ganglionic cells of these parasites. They are confined to 
the middle and hinder parts of the body where they are more or less 
regularly arranged. Blue-coloured branched cells were more common 
in the anterior third of the body. They are not isolated elements, but 
are specially grouped around the cerebral commissure. Cells that stain 
blue were also found in the suckers and in other muscular organs such 
as the pharynx ; they may be distinguished from the peripheral elements 
by their somewhat smaller size. In good preparations, and with high 
powers, it was often possible to follow the processes of the cells for a 
* Arbeit. Zool. Zoot. Inst. Wurtzburg, x. (1895) pp. 127-64 (3 pis.). 
t Tom. cit., pp. 167-88 (1 pi.). 
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