PARORCHIS ACANTHUS, A NEW TREMATODE. 353 



oval, pretty close in front of tlie testes, almost median. 

 Shell gland well developed. Receptaculum semiuis small, 

 between the testes. Laurer's canal present. Yolk-glands 

 not extensively developed, composed of unequal follicles ; 

 situated for the most part close to the outer side of the 

 intestinal diverticula, and extending between the ventral 

 sucker and the testes. Uterus also confined between the 

 latter limits ; convolutions fairly numerous, and having a 

 transverse direction from side to side of the body. Eggs of 

 large size, with light yellow shell, containing even at some 

 distance from the genital aperture a fully developed Miraci- 

 dium larva. 



Habitat. — The terminal portion of the intestine of birds. 



Type. — Parorchis acanthus, mihi. 



In my previous description of the type I made mention of 

 the remarkable similarity which it bears to Distomum 

 pittacium, Braun, apart from the fact that the latter form 

 entirely lacks spines. Further investigation of Parorchis 

 acanthus has convinced me that the two species are very 

 closely related, and, indeed, differ only in minor details. 

 The outstanding feature of distinction is the absence of 

 spines in Distomum pittacium. I am inclined to believe, 

 however, that this difference does not actually exist, and that 

 the spines have been removed as a result of the method of 

 preservation, and their traces unnoticed by Braun. As far 

 as I can gather, his description is based on a single specimen 

 from the Vienna Museum collection, and he has had no 

 opportunity of examining the living animal. 



Immersion in a weak acid solution for even a compara- 

 tively short time causes the spines to disappear wholly or in 

 great part, and something of this nature has possibly occurred 

 to Braun's specimen. The circum-oral collar, of which one 

 would have expected at least a trace to remain, is not repre- 

 sented in his figure, but, in the absence of spines, it might be 

 apt to be passed over. As sufficient ground for venturing 

 the foregoing supposition I would adduce the remarkable 

 similarity in the internal structure of the two forms. It is 



