bY E. F. HALLstANJi. - 53d 



niejrascleres scattered between the fibres are relati\elv fev, and 

 consist of styli only, similar to those composing the fibies. But 

 at some distance from the surface, — usually a somewhat con- 

 siderable distance, megascleres of a second kind make their 

 appearance,- Hexuous strongyla and tornota, — which increase 

 in number towards the deeper portions of the sponge and eventu- 

 ally become very abundant; indeed, it is almost as much to the 

 increased multitude of the latter, as to augmentation in tlie 

 quantity of the spongin, that the greater density of the skeleton 

 in the stalk and other older portions of the sponge is due. A 

 considerable proportion of the latter spicules are developed in 

 close contiguity to the fibres, and ultimately, owing to tlie sul)- 

 sequent formation of additional spongin, become completely 

 united to them. The presence of these flexuous megascleres, 

 owinir to their extreme rarity in, or total absence from, those 

 portions of the sponge usually selected for examination, hitherto 

 has escaped notice. 



Through all parts of the sponge there are scattered small 

 sigmata singly in moderate abundance, trichodragmata of three 

 kinds, and single trichites of similar size to those composing the 

 larger trichodragmata. The trichodragmata of two kinds are in 

 the form of neat sheaves of extremely slender trichites, and 

 differ from each other onlv in length: the shorter of these are 

 almost as numerous as the sigmata, while the longer are rela- 

 tively scarce. The dragraata of the third kind are composed of 

 trichites equal in length to those of the just-mentioned longer 

 dragmata, but stouter and more fusiform, and occur for the 

 most part in dense masses of irregular shape and size, which 

 refract the light in such a way as to appear blackish and opaque, 

 and are, therefore, very noticeable although comparatively 

 scarce; some of the largest of these aggregations exceed 200/x in 

 breadth. The singly scattered trichites, or microxea, are moder- 

 ately scarce in the interior, but more plentiful near the surface. 



Megascleres. — (i.)The styli are invariably more or less curved, 

 are usually evenly rounded at the base and of uniform or nearly 

 uniform diameter therefrom to beyond the middle of their 

 length, and almost invariably taper throughout the remainder 



