12 PROF. E. A. MINCHIN ON THE [May 2, 
considerable time after each washing, the spicules were transferred 
to the slides by means of a pipette. 
“Hach slide, when ready, then had marked upon its under 
surface twenty circular areas, each being brought into the micro- 
scopic field in turn and all spicules in each area carefully counted. 
When all the spicules were counted the circle was erased and the 
next circular area dealt with. 
“The counting was done with the aid of a camera lucida and 
three differently coloured crayons, thus ensuring that all spicules 
were counted and counted once only. 
“Hach quadriradiate spicule had a number in blue marked upon 
it; the triradiate spicules were marked with successive red 
numbers and a green number noted a monaxon. At each 
counting a check could be made, and the counting was complete 
when each spicule was seen to have one number of a special 
colour upon it.” 
The spiculation of Clathrina contorta thus shows, on the one 
hand, comparatively slight variation in the triradiate systems, and, 
on the other hand, extraordinary differences in number and size 
of the monaxons in different specimens. The variability is so 
marked, and the monaxons are frequently so difficult to find, as 
to suggest at once a possible extreme of variation in which the 
monaxons would be totally absent. Were this to occur we should 
have a variety of the sponge characterised by a type of spiculation 
which would lead to its being placed, in many current systems of 
classification, in a genus distinct from the variety in which 
monaxons occur. 
As a matter of fact, I may state at once that the variety of 
contoréa in which monaxons are completely lacking is very common, 
and it has been described by Lendenfeld from the Adriatic under 
the name of Ascetéia spinosa, This is no mere surmise on my part ; 
I have been able to examine, in the collection of Canon Norman, 
a slide obtained by him from Lendenfeld, and bearing in Len- 
denfeld’s handwriting the label “ Ascetéa spinosa.” Text-fig. 4, 
5 a—5 h, vepresents some spicules drawn by me from this slide. 
As will be seen, the spiculation differs in no single particular from 
that of the true contorta, except for the lack of monaxons. Since 
the preparation consists of tubes of the sponge mounted whole, it 
was not possible to obtain profile views of the gastral rays, except 
at the torn ends of the tubes, and in no case was I able to see an 
unbroken gastral ray in side view, but the fragments which I have 
drawn (5/5 h) are sufficient to prove that the gastral rays of this 
specimen attain the degree of length and slendernegs characteristic 
of the species. Lendenfeld’s specimen is, in fact, identical in 
character with other specimens of “spinosa” which I have from 
Banyuls (text-fig. 4, 6 a6 g), and these again differ in no respect 
from the true contorta except for the absence of monaxon spicules. 
If Ascetta spinosa Lend. is to be regarded, as I believe, merely 
as a variety of Ascandra contorta H., how is this variation to be 
explained? The specimens of spinosa that have come under my 
notice agree perfectly in external characters with contorta, but are 
