166 
an inch long; they are ‘2 of an inch in length, and terminate 
each in a double claw, with an expanded pulvillus, clypeus, 
Twice natural size. 
somewhat heart-shaped, lighter in colour than the rest of the 
body, which is deep chestnut-brown ; stigmata ventral at the 
apex of the triangular ventral depression, and in a small 
sulcus posterior ; rostrum small, conical. This specimen is 
thus of very large size and firm and tenacious in the consist- 
ence of its integument. Several species of the genus are 
described from Australia, but they are all, as far as I am 
aware, reptilian parasites with this exception. 
Dr. Royston-Picott’s RESEARCHES.! 
- _ Tue great interest which attaches to all researches directed 
to the improvement of the microscope, and especially to the 
invention by which Dr. Royston-Pigott claims to increase 
magnifying power, without, in the same degree, diminishing 
focal distance, make us desirous of laying before our readers 
as complete an account of them as possible. We have, 
therefore, gladly availed ourselves of the kind permission of 
the Council of the Royal Society, and of Dr. Pigott himself, 
to reproduce the substance of a paper communicated by him 
to the ‘ Philosophical Transactions,’ and the illustrative 
plates, without which, in fact, much of what he has written 
would be unintelligible. 
1*On a Searcher for Aplanatic Images applied to Microscopes, and its 
Effects in Increasing Power and Improving Definition.’ By G. W. Royston- 
Pigott, M.A., M.D. Cantab., M.R.C.P., F.C.P.S., F.R.A.S., formerly Fel- 
low of St. Peter’s College, Cambridge. 
