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. 



" Each 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. 



" Each qviadriradiate 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 difierent 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 

 contorta in which monaxons are completely lacking is veiy common, 

 and it has been described by Lendenfeld from the Adriatic under 

 the name of Ascetta 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 " Ascetta spinosa." Text-fig. 4, 

 5 «-5 h, represents some spicules drawn by me from this slide. 

 As will be seen, the spiculation differs in no single particulai- 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 i^ay 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 slenderness 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, 6a-6^), and these again differ in no respect 

 from the true contorta except for the absence of monaxon spicules. 



If Ascetta sjnnosa Lend, is to be i-egarded, 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 



