55 
Inner surface of the inter-ambulacral region of the shell. Its 
spicula (fig. 7) are in the form of triangular perforated plates, 
derived from the enlargement of a tri-radiate spiculum, which 
first forms and subsequently has its angles filled up, leaving 
the holes, which are so constantly found lightening the other- 
wise dense shells of these animals. Mixed with these are 
a few spicula, which from the greater size and length of one of 
their radii, have assumed more the character of spines. 
The spicula of other internal parts vary greatly in the 
species ; as a rule, they are coarser and more numerous where 
the fibrous membranes are themselves thickest, but I will not 
describe their varieties, as the object of the present paper is 
only to indicate the value of the minute structure of these 
animals as an aid to their generic distinctions. 
Briefly in summing up one may say that: 
a. The spines of the recent Cidaride are characterised by 
the dense crust which terminates their growth. 
b. The pedicellariz, by the special chamber foundin each jaw, 
and by the calcareous stem divided into two parts, the upper 
being in immediate contact with the head. 
e. The ambulacral tubes, by being surrounded by the con- 
centrically curved spicula, which give them a ringed 
appearance. 
These three characters are common to, and only found in, 
all recent Cidaride (the fossil forms are not alluded to, as 
they do not admit of a complete and satisfactory examination). 
d. The ovary, strengthened by triangular plate-like or 
tri-radiate spicula (the former most abundant), but not 
retaining the form of its component tubules, in the dry state 
affords a feature constant and peculiar to this genus. 
Notrres on the Metuop of AppiicaTION of NITRATE of 
Sitrver and CHLoRIDE of Gop in the PREPARATION 
of Certain TissvEs for Microscopic INVESTIGATION. 
By Henry N. Mosetey, B.A. Oxon., Radcliff Travelling 
Fellow. 
Iv is hoped that the following notes may be of service to 
some of the readers of the Quart. Journal of Microscopical 
Science. I have this year spent six months in the labora- 
tories of Professor Stricker in Vienna, and have worked with 
the microscopes under his assistant Dr. Klein, to whom 
I am indebted for the greater part of my knowledge of the 
methods here described, 
