114 Macieay Memortat VouuMeE. 
excretory character. Unlike similar granules that occur in some Rhabdocceles* they 
are confined to the alimentary epithelium and do not extend to the parenchyma. 
Between the ordinary epithelial cells there are narrow tubular cells with enlarged 
and rounded inner ends, full of granules, which become very darkly coloured with 
carmine or hematoxylin, but are transparent and colourless in the unstained condition. 
These cells frequently bifurcate. Their granular contents are probably of the nature 
of a digestive secretion. Similar cells—the so-called ‘“ Kornerkolben”—have been 
described by v. Graff and others as occurring among the epithelial cells of the 
intestine in some 7x7bellaria; and Kerbertt observed them also in a Digenetic 
Trematode. 
1TX.—Tuer Excretory System. 
When I published my former account of Zemnocephala the mode of opening of 
this system on the exterior by two dorsally and anteriorly placed apertures seemed 
quite exceptional among the Trematodes. It has since been shown, however, that 
this is not the case. A similar arrangement is found to prevail in Polystomum, 
Diplozoon, Octobothrium, Sphyranura, Axine, Microcotyle, Gyrodactylus, Dactylogyrus, 
Pseudocotyle, and Tristomum and other Trzstomide, in tact, as pointed out by Braun,t{ 
the supposition that ventral openings occur was the result of an error, But in 
several other respects the excretory system of 7emnocephala differs widely from that 
of other Trematodes—so far as known. 
Each of the two excretory pores of Zemnocephala and Craspedella leads into a 
thick-walled terminal vesicle or excretory sac (PI. x. fig. 11), which is of pyriform 
shape, but somewhat bent on itself at the apex. The sac is contractile, the contrac- 
tions being brought about by the agency of a complete layer of muscular fibres 
(fig. 13, wzw.). Surrounding the orifice there is also a set of muscular fibres by means 
of which the aperture can be contracted or dilated. The wall of the sac is of 
protoplasmic material, having in the fresh state a yellowish colour; examined in 
sections (figs. 13 and 14) it proves to be finely fibrillated. In the wall of the main 
part of the sac there are no nuclei, but in the wall of the curved narrow apical 
portion is a large nucleus, and a second lies a little further on in the wall of the main 
canal. Those two nuclei were formerly supposed by me to be the nuclei of nerve-cells 
closely applied to the terminal vesicle. The re-examination of series of sections 
(Pl. x. fig. 14) has, however, shown me that this was an error, and that the nuclei in 
question—which are of exactly the same character as the nuclei of the excretory cells 
* Bohmig, /.c. p. 239. 
+ ‘‘ Beitrag. zur Kenntniss der Trematoden.” ‘Arch. f. Mikro, Anat.’ XIX. p. 529 (1881). 
+ ‘*Ueber die Lage des Excretionsporus bei den ectoparasitischen Trematoden.” ‘Zool. Anz.’ XI. (1889), and 
“Ueber Temnocephala.” ‘Centralbl. f. Bacteriologie u. Parasitenkunde,’ VII. Bd. (1890). 
