and Physiology of the Spongida. 19 



scopically, we shall find that its base is composed of a granu- 

 liferous, almost transparent, living substance like jelly. It 

 is this living, locomotive, apparently structureless substance, 

 to which I have before alluded, which holds all the rest to- 

 gether, and, originating in its simplest form in the ovum, as 

 will be shown hereafter, finally evolves all that is subsequently 

 developed in the sponge. 



Of its living nature we, of course, can have no idea except 

 from its manifestations ; and of these I can offer no better 

 description than I gave in the 'Annals' for 1849, vol. iv. 

 (pp. 87 & 91, pi. iv. fig. 2), in the following passage, which 

 will be found at p. 91 : — 



"If a seed-like body [of Spongilla] which has arrived at 

 maturity be placed in water, a white substance will, after a 

 few days, be observed to have issued from its interior through 

 the infundibular depression on its surface, and to have glued 

 it to the glass ; and if this be examined with the microscope, 

 its circumference will be found to consist of a semitransparent 

 substance, the extreme border of which is extended into digital 

 or tentacular prolongations, precisely similar to those of the 

 Protean, which in progression or polymorphism throws out 

 parts of its body in this way (pi. iv. fig. 2, c). In this semi- 

 transparent substance may be observed hyaline vesicles of 

 different sizes, contracting and dilating themselves as in the 

 Protean (fig. 2, d) ; and a little within it the green granules, 

 [germs] so grouped together (fig. 2, e) as almost to enable the 

 practised eye to distinguish in situ the passing forms of the 

 cells [" spherical cells " of the seed-like body] to which they 

 belong. We may also see in the latter [these "cells"] their 

 hyaline vesicles with their contained molecules in great com- 

 motion, and between the cells themselves the intercellular 

 mucilage (fig. 2,/)." The "intercellular mucilage" is the 

 " semitransparent substance " above noticed, and for which I 

 have above used the term " intercellular sarcode." 



For another description of the " intercellular mucilage" see 

 p. 87 of 'Annals ' (I. c). Thus in 1849 attention was directed 

 to this primordial plasma. 



The sarcode proper (for thus the " intercellular mucilage " 

 might be designated) envelops the whole of the fibre, and, 

 filling up the interstitial spaces of the skeleton, forms an 

 areolar structure, which is densely charged with the " ampul - 

 laceous sacs," the " ova of the sponge," " muscular cells," 

 together with various other kinds of cells not yet described 

 if even recognized, and the " flesh-spicules ;" while the mass 

 generally is traversed by the inhalant and exhalant or excre- 

 tory tubular branched systems — the former descending from 



9» 



