DUBLIN MICROSCOPICAL CLUB. 339 



Arctic Desmidiese delineating the very form in question. (Ofversigt 

 af Kongl. Yetensk.-Akad. Porhandl, 1875. No. G, t. vii, f. 15.) 

 Its oblong, rectangular zygospores call to mind those of Penium 

 Mooreanum, Archer, but they want the nipple-like prolongations 

 at the angles, as in that species, but like them they often appeared 

 twisted, even so much so that the planes of the opposite ends of 

 the zygospore might be at right angles to one another. 



llth February, 1876. 



Lejeunia ecliinata exliibited. — Dr. Moore showed Lejeunia 

 ecliinata, and pointed out the mode of fructification in this species. 



New species of Tcenia exhibited.— Dr. Macalister showed a new 

 species of Taenia which be named T. Hyracis, and of which he 

 would hereafter publish a description. 



JExhibition of sections of Spine of Phyllacanthus annulifera. 

 — Mr. Mackintosh showed cross sections of the spines of Pliylla- 

 canthus annulifera, A. Agaz., which presented the usual cidaroid 

 characters. 



Ex'hibitio7i of Crystals of Xanthine Sulphate. — Mr. B. Wills 

 Eichardson exhibited a very perfect stellate mass formed of 

 Crystals of xanthine sulphate mounted in Canada-balsam. He, 

 at the same time, reminded the members present that in De- 

 cember, 1872, he exhibited crystals of the hydrochlorate, the 

 nitrate, and also the sulphate of xanthine. An illustrated de- 

 scription of the hydrochlorate appeared not long afterwards m the 

 ' Quarterly Journal of Micr. Sci.' to which he referred those who 

 might require further information about them. The specimens 

 of the sulphate exhibited on that occasion were not so perfect, 

 however, as he could have wished, having been more or less in- 

 jured in the attempt to clean them for mounting. Having 

 originally but little more than a couple of grains of xanthine 

 (from human urine) to act upon, of which only about a grain 

 remained after the formation of the crystals he had described, he 

 determined to try if he could prepare some more crystals of the 

 sulphate and, if successful, to mount them without any attempt 

 to clean them. Accordingly he placed about a quarter to half a 

 grain of the xanthine on an ordinary slide, and then added to it 

 a little pure sulphuric acid. The slide was placed in a cabinet, 

 secured from dust. Crystallization slowly took place which en- 

 ded in the formation of the very perfect stellate mass now under 

 the microscope. It was not until the expiration of two years 

 that the specimen was sufficiently dry to allow of his mounting it 

 in Canada-balsam. During the slow process of drying, if it could 

 be called such, he occasionally removed superfluous acid with small 

 pieces of bibulous paper. The crystalline mass was globular and 

 studded with long projecting crystals, some of which were fa- 

 cetted and appeared to belong to the triclinohedric system, but of 

 this he did not wish to speak too positively. In the polariscope, 



