PROCEEDINGS OF THE SOCIETY. 
555 
rays wore symmetrical on both sides of the optic axis, they were figured 
on one side only. Prof. Schellbach’s was recognized as the most perfect 
work of the kind known. 
The President announced the death of Prof. P. Martin Duncan, F.R.S., 
who, as a past President of the Society, was well known to most of the 
Fellows on account of the active and efficient manner in which he per- 
formed his duties during his occupation of the chair, and was equally well 
known to others through his great work on the Echinodermata. His sad 
death occurred on May 29th. 
Prof. Bell said that, as the only officer of the Society present who held 
office during the presidency of Prof. Duncan, he rose to give expression to 
the regret which he felt at the loss the Society had suffered by Prof. 
Duncan’s death. Prof. Duncan was one of the few remaining naturalists 
who were not merely specialists. His early contributions to botanical 
science were succeeded by very important contributions to geology, in 
which he not only dealt with fossils as such, but also in their relation to 
the fauna of Australia and elsewhere. The work to which the President 
had alluded was produced later on. His work as a Fellow of the Society 
was that of one of the older microscopists who laid great stress upon 
the use of the lower powers. The appreciation in which he was held 
was best shown by the fact that the ordinary bye-laws of the Society 
were suspended in order to keep him in office for a longer period than 
usual.' Those who knew him personally would regret that there had passed 
away from among them one whom they could not meet without feeling 
the happier for the meeting, and it would add to the sorrow of those 
who thus knew him in health to know that he lay for many months 
previous to his decease in a condition of almost intolerable suffering. 
His name would be remembered with affection by all who had come 
intimately into association with him. 
A negative of Amphipleura pellucida, recently produced with Zeiss’s 
new 1/10 of 1* 6 N.A. and sunlight, by Mr. T. Comber, of Liverpool, was 
exhibited, and his letter was read suggesting that the want of sharpness 
was due to the employment of a projection eye-piece for a tube-length of 
160 mm., whereas the objective was made for a tube-length of 180 mm. 
The illumination was axial with a Zeiss achromatic condenser of 1 • 2 
N.A. Mr. Comber thought the resolution showed indications of so- 
called “ beading,” and hence he inferred that the ultimate resolution 
would be shown to be similar to that of its congener Amjphipleura Lind - 
lieimeri. The mounting medium had a refractive index of 2*2, but was 
very unstable, granulations appearing in a very short time. The nega- 
tive showed these granulations, though the object had only been mounted 
two or three days. 
Mr. Mayall expressed his surprise at the want of sharpness in the 
definition, especially as the manipulations were conducted by so careful 
and accurate a microscopist as Mr. Comber. He regretted that Mr. 
Comber had not had a projection eye-piece corresponding precisely with 
the tube-length of the objective, so that his trial of that particular objec- 
tive might have been regarded as authoritative. This was the more 
