104 
Nodoubt it is well worthy future research, and to that it must be 
left. Greeff, in a note (p. 402), remarks that, “ Regard being had 
to its peculiar structure, the rhizopod in question cannot be relegated 
to Amcebe proper, nor, on account of its Amceba-like movements and 
want of radiating pseudopodia, to the Actinophryans, but rather 
represents a special form.’ And so it zs, provided only it be not a 
congeries of individuals of Actinospherium ichhornu (called 
Actinophrys Eichhornii by Prof. Greeff—Mr. Archer would venture 
to think wrongly, for that form is something a good deal more than 
an Actinophrys) ; but under such a supposition it must be admitted 
the specimens of Actinospherium would have suffered much modi- 
fication, losing the most characteristic features and gaining others to 
an extent that would be sufficiently surprising. Doubtless Greeff 
will ere long be in a position to shed a light upon this as yet 
enigmatic form, and so must it for the present be left in 
abeyance. 
Royat Microscopican Sociery. 
October 12th, 1870. 
Read papers on the “‘ Coralliospongia, or Anastomosing Sponges,’ 
by Mr. W. S. Kent. 
“On Aplanatic Illumination and Aplanatic Definition,” by Dr. 
G. W. Royston-Pigott. 
At the reading of this paper Professor Huxley was present. 
He said that being practically interested in researches such as 
those which Dr. Pigott was conducting with so much ability, 
and having seen his paper in the ‘ Proceedings’ of the Royal 
Society, he had been much struck by it, and being very much 
in want of means of looking through tolerably thick glass under 
a high magnifying power, he made it his business to ask Professor 
Stokes about Dr. Pigott. The reply was so favorable that he 
wrote to Dr. Pigott for assistance, by whom he was told to apply 
to Messrs. Powell and Lealand, who made an aplanatic searcher 
for him; and he (Professor Huxley) having used it frequently, 
must bear witness that there was no sort of doubt as to the won- 
derful illuminating power it possessed, combined also with the 
great magnifying power which could be got out of a compara- 
tively low object-glass by the use of this instrument. But when 
the attempt was made to go farther, that is to say, when the 
instrument was applied to deeper object-glasses (it might be from 
want of proper knowledge in the use of it), it did not seem to be 
of much use. It was an exceedingly important practical question 
