PROCEEDINGS OF THE SOCIETY. 1065 



were employed either within or without the focus, a circular diaphragm 

 would cut off more or less of the oblique light : but the central portion 

 used, unless reduced to a very small pencil, would still consist of sensibly 

 oblique rays, because it was part of a solid cone of light. If strictly 

 central parallel rays were to be employed, only a very small pencil 

 would have to be utilised by means of a system of collimating dia- 

 phragms. He was not aware that any important results in microscopy 

 had been obtained by the employment of such a pencil of light. A great 

 deal too much was claimed on behalf of what was termed central light, 

 regardless of the fact that some images could not even be glimpsed with 

 the finest objectives in existence unless the illumination was limited 

 to an intense beam of light of the highest obliquity the objective .would 

 transmit. 



The President said they had received two exquisite photomicro- 

 graphs of Amphipleura pellucida from Mr. E. M. Nelson, which would be 

 found well worthy of inspection. 



Mr. H. B. Brady's paper " On the Keproductive Condition of Orbi- 

 tolites complanata, var. laciniata" (ante, p. 693) was communicated to 

 the meeting by Prof. Bell, who said that the interest of the subject 

 attached to the information given on a vexed point connected with these 

 organisms. Two French naturalists had pointed out that there were 

 what they called two forms, one of which had a small number of large 

 chambers, and the other had a large number of small chambers. These 

 they called form A and form B, and though there was nothing to show 

 that there was any distinction of sex, it had been said that A and B were 

 the males and females of the species. Mr, Brady came to the conclusion 

 that the young forms were the result not of sexual intercourse of any 

 kind, but of a process of gemmation. 



Mr. Dowdeswell's letter was read, accompanying some photomicro- 

 graphs of spermatozoa from the Triton : — 



" I have the pleasure herewith to hand to the Society photographs 

 of the spermatozoa of the Triton, showing with perfect distinctness the 

 minute barb on the extremity of the head, the existence of which, I 

 believe, has been doubted, but is here unmistakably evident. The 

 photographs are admirable, and reflect great credit upon Mr. Andrew 

 Pringle, of Cromwell House, Bexley Heath, Kent, who took them. If 

 the barbs are not shown with absolute sharpness, I can testify that they 

 are at least as distinct as in the preparation from which they are taken, 

 which is five years old, and has become materially altered. 



" I must beg to be allowed a few words of ' personal explanation,' and 

 a reclamation, though not for myself. In my first mention of the 

 existence of this process (Quart, Journ. Micr. Sci., 1882, p, 73), I stated 

 that it had been first observed and pointed out to me, in a preparation I 

 had given him, by Mr. E. M. Nelson ; but in the fuller notice, with 

 drawing of it (ib. 1883, p. 336), which, being sent in late, was printed 

 without a proof being sent to me for revision, I omitted to state this, 

 and overlooked the omission till I saw the barb referred to as a discovery 

 of my own. At the time, intending to publish some further observations 

 on the subject, I omitted to correct this, and take this opportunity of 



