1905] Wilson — Sponges. 39 



by specimens of Hyalonema fteteriferu?n, Caulophacus schulzei, 



Thenea fenestrate!, Petrosia variabilis crassa. In Eurete the 



spiral form of body beset with cup-like outgrowths varies 



towards a bilateral symmetry. In Tylodesma alba massive 



and lamellate bodies occur, as parts of one continuous speci- 

 men. In Gellius perforates a uniform habit of growth may 



result in very different body shapes. In Thenea individuals 



the number and size of pore areas vary; also the spicular 



fring-e round the osculum. In Iofihon lamella the character 



of the surface varies in different parts of the same individual, 

 owing- to the divergence in character of the main efferent 

 canals and their apertures, and to the varying- amount of col- 

 lenchyma round such canals. 



2. Variation in same individual in the skeletal framework, 

 or the skeleton in general. 



In Chonelasma calyx the tuberculation of the beams of the 



dictyonal framework varies. In Hexactinella ventilabrum 



there is considerable variation in the way in which the hex- 

 acts combine to form the dictyonal framework. In Thenea 



fenestrata there is variation in the development of the spicu- 

 lar fringes round the pore areas. In Petrosia variabilis 



crassa and in Petrosia similis densissima a skeletal reticulum 



remains undeveloped in spots. In Pachychalina acapulcen- 



sis the skeletal framework in places is fairly regular, although 

 in general irregular. In Phakellia la?nelligera the skeletal 



lamellae vary in respect to branching-. In Petrosia similis 



densissima over seme parts of the surface there are no projec- 

 ting spicules, while over other parts such spicules are present 

 in consideral number. In Gellius perforatns there is consid- 

 erable variation in the character of the spicular tufts which 

 project from the surface. In lofthon la?nella there is varia- 

 tion in the number of spicules which combine to form the 

 side of a skeletal mesh. 



j. Uncorrelated Variation in the megascleres of an Individ' 

 ual, i. e. variation apparently not correlated with the structu- 

 ral peculiarities of the body-locality. 



