PROCEEDINGS OF THE SOCIETY. 319 



originals, and from these negatives the plates have been heliotyped. I 

 am aware that the heliotypes have many faults, and I am only fully 

 satisfied with the plate III. fig. 5. However, I should be pleased 

 to have them presented to the Eoyal Microscopical Society if you 

 think them of sufficient interest. My negatives have not all the same 

 power of light, and this circumstance makes it difficult to obtain good 

 prints of more from the same plate ; the double process of photo- 

 graphing the plates — which was rendered necessary because my 

 negative glass plates had not all the same thickness — has also tended 

 to impair the heliotypes. That will easily be seen by comparing the 

 plate III. fig. 5 with the inclosed plate IV., which is heliotyped 

 direct from my negative. In the future I shall only use plate-glasses 

 of the same thickness for my sensitive plates." 



Dr. Braithwaite thought the photographs were very excellent but 

 feared that the plates were not sharp enough. 



Mr. Crisp exhibited a new form of Abbe's condenser, the mounting 

 allowing it to be used with the smaller stands, and the diaphragm 

 consisting only of a sliding plate pierced with four apertures of 

 different sizes. 



Mr. Ingpen, in reply to a question, said there would be no diffi- 

 culty in using this condenser with a proper rotary stage. He could 

 not say that it would be in all respects as convenient as the larger 

 form, but against this must be set the fact that there were many 

 small instruments in use upon which the larger one could not be used 

 at all. 



Mr. Crisp read the leading points in Prof. Thoma's description of 

 his microtome (see p. 298). 



Mr. Groves exhibited and described a new form of frog-plate . 



Mr. Busk's note on Paper Cells was read. 



Dr. Hudson's paper on "Five New Floscules, with a Note on 

 Prof. Leidy's Genera oiAcydus and Dictyophora " was read (see p. 161) 

 and illustrated by drawings enlarged upon the board by Mr. Stewart. 



Mr. Crisp thought it a matter for remark that at this day five new 

 species of such a Eotifer as Floscularia should have been found. 



Mr. Ingpen said that they had been obtained from quite new 

 ground near Dundee. 



Prof. Bell remarked that one of the five had since been found by 

 Mr. Bolton near Manchester. 



Mr. Badcock thought it ought to encourage collectors to search 

 much more carefully in their old localities, though these, unfortu- 

 nately, were becoming more and more reduced in consequence of 

 encroachments. 



Mr. Waddington read his paper on " The Action of Tannin on 

 the Cilia of Infusoria " (see p. 185). 



