1905.] 



SPONGE CLATHRINA CONTORTA. 



11 



moiiaxon or an abnormal triradiate (text-fig. 3, Sf); probably it 

 is both ! My friend Mr, Alford has also found, in the slide of 

 Topsent 12 e, four abnormal monaxons which have additional rays 

 growing out laterally and thus become triradiates (text-fig. 6, 

 9 «-9 c). In one of these (9 b) the three rays are approximately 

 equal in size and meet at the angles of an ordinary triradiate. 

 For all these reasons I consider there is much to be said for 

 regarding the monaxons of contorta as secondary monaxons 

 derived from a triradiate system by suppression of one ray and 

 hypertrophy of the two remaining, wliich become placed in the 

 same straight line, or neai^ly so. 



The numerical variation in the monaxons is not less re- 

 markable. In some specimens scarcely any monaxons are to be 

 found ; in others they are extremely abundant. Thus in a 

 specimen recently examined by me, I took a fairly large piece of 

 the sponge, separated the spicules with Eau de Javelle, and 

 mounted all I could get up with the pipette, covering three slides. 

 After prolonged searching I found five monaxons to many 

 thousands of triradiate systems. In another specimen in which 

 I could find no monaxons, Mr. Alford by careful searching found 

 two. It is often extremely difiicult to be certain if a specimen 

 has monaxons or not. Mr. Alford has kindly undertaken for me 

 the task of counting the numbers of each kind of spicule found 

 in different specimens, with the following results : — 



These results were obtained in the following way : — '' Each 

 specimen was put into Eau de Javelle to separate the spicules, 

 and after careful washing, and being- allowed to stand for some 



