MEMORANDA. 115 
very well. The action of the roughened glass is similar to that 
of the paraboloid, but not to the same degree. The screens 
are prepared in a few minutes, by rubbing two glass slips 
together with emery powder and water between them. It is 
well to have two screens, one finely, and the other more 
roughly ground, so as to vary the effect according to the 
subject under examination. The instrument used is one 
of Smith and Beck’s largest size; the objective by Ross.— 
Joun Keares, Liverpool. 
Notes on the Calcareous Corpuscles of Tricuspidaria.—By T. 
Srencer Cossoip, M.D., F.L.S8., Lecturer on Botany, St. 
Mary’s Hospital, London. 
The clear manner in which Claparéde appears to have de- 
monstrated a relation subsisting between the calcareous 
corpuscles and the excretory system of vessels in the Trema- 
toda, induces me to call attention to these bodies in the 
Cestoda, and especially in Tricuspidaria nodulosa. It would 
seem that Dr. Guido Wagener had long ago discerned this 
connexion in the Flukes; but as he had not published his 
views on that point, it is to the former observer that we are 
mainly indebted for this interesting discovery. 
In the Cestode Tricuspidaria—often synonymised Trieno- 
phorus nodulosus—narrow vessels may be easily recognised, 
passing off continuously from the membranous capsules 
investing the sclerous corpuscles; these vascular prolonga- 
tions, however, instead of forming inosculations, as in Tre- 
matodes, are single, and have their very limited course 
directed outwards towards the clear structureless epidermis. 
It is highly probable that they open at the surface, but I 
have never been able to detect the slightest indication of 
such an aperture. 

Portion from the margin of the head of Pricuspidaria nodulosa. The vas- 
cular prolongations connected with those corpuscles which are not in focus 
are either only partially seen or cannot be observed at all. This specimen 
was removed with others from theintestine of a Pike. Drawn with the 
aid of a camera; X 300 diameters. 
Dr. Wagener figures a structure precisely analogous to this 
in plate xxix, attached to his Haarlem Prize Essay, the 
