40 Journai, of thk Mitchfjj, Society. [March 



As regards size of the spicules, there seems to be noticeable 



variation in all sponge species. The shape of one of the 



macramphidiscs varies considerably in Hyalonema bianchora- 



tum. In Caulophacus schulzei the principal hexacts are 



occasionally tuberculated, and in the same species the tuber- 

 culatum of the pentacts varies. The character of the diact 



ends varies commonly, e. g. in Balky dorus lev is spinosus. 



In Farrea mexicana the pentacts vary in respect to tubercula- 

 tum. In Eurele erectum the character of the distal ray of 



the gastral pinules varies extensively. In Petrosia variabi- 

 lis crassa the oxea sometimes assumes the shape of a stron- 



gyle, or style. In Pefmres foliaformis the triaenes vary 



considerably. In Pachychalina acapulcensis the size of the 



oxea varies within wide limits. — In Phakellia lamelligera 

 the oxeas and the two kinds of styles all vary considerably in 

 shape. 



^. Uncorrelated variation in the microscleres of an indi- 

 vidual. 



The microscleres as well as the megascleres very commonly 

 vary in size and detailed shape, although in them, as in the 

 megascleres, there is a size and pattern which are character- 

 istic of the individual (species), i. e. to which the majority of 

 the spicules of an individual conform. 



Some striking cases of variation are afforded by the micro- 

 oxyhexacts of Hyalonema bianchoratum, plesiasters and spir- 

 asters of Thenea fenestrata, sigmata of lylodesma alba. 



j. Correlated variation in the spicules. 



In some cases the variation of spicules is obviously not 

 ungoverned by the rest of the body, but is correlated with 

 body-locality. 



Thus while the pentacts in Hexactinella labyrinthica vary 

 at large in respect to length of the several rays, the pentacts 

 overlying the larger inhalent canals commonly have noticeably 

 short proximal rays. Such a phenomenon would customarily 



be referred to as "adaptive." The variation of dichotriae- 



nes towards the protriaene type, round the pore areas of 



