1905.] 



SPONGE CLATHRINA CONTORTA. 



19 



identity of contorta and s^ntiosa, it is liai'dly necessary for me to 

 express my opinion with regard to those systems of classification 

 which define not only species but even genera of Ascons by the 

 presence or absence of monaxon spicviles. Before such a character 

 as the presence or absence of monaxons can be used for systematic 



Text-fig. 6. 



Abnormal gigantic spicules of the class of the monaxons from a specimen of Clathrina 

 contorta from Banyiils (Topsent 12 e). Magnified about 150 linear {i. e. half as 

 much as the spicules figured in text-figg. 2-5). 



purposes, it is necessary to understand clearly what is meant by a 

 monaxon spicule. In calcareous sponges a spicule of this class may 

 be one of two perfectly distinct things. It may be, on the one hand, 



2* 



