and Physiology of the Spongioid. 31 



skeleton, so there is one as exclusively connected with the 

 sarcode of the sponge ; hence the latter has been called " flesh-" 

 in contradistinction to the " skeleton-spicule." They are 

 objects for the most part of singular beauty, from their often 

 complicated and symmetrical forms, of infinite variety, of 

 microscopic minuteness, and dispersed, without any appreciable 

 regularity or constant quantity, more or less abundantly through- 

 out the sarcode. One or more forms may exist in the same 

 sponge, and thus they become of much importance in specific 

 distinction ; but as they do not exist in all sponges, this ad- 

 vantage is not general; while their extreme minuteness, causing 

 them to fall through the skeleton when the sarcode in which 

 they are imbedded putrefies and becomes washed out, as small 

 pebbles pass through the meshes of a large net, still further 

 deprives us, as before stated, of their specific aid in most of 

 the sponges, which never come to hand in any other form than 

 the skeleton. 



Where they are present, they may be of use in giving greater 

 firmness to the sarcode — that is, by acting as a kind of sub- 

 skeleton ; hence Dr. Bowerbank has called them " retentive 

 spicules :" but as they are frequently absent, and, indeed, the 

 skeleton-spicules, too, in some sponges, the latter can evidently 

 do without them, so we must look for some other bond of 

 union for the sarcode ; and this, which may be found in the 

 contractile power that it possesses during life, but which 

 immediately disappears on death, is well exemplified in the 

 calcareous sponges, as before stated, where these, the tenderest 

 of all sponges when dry, grow upon rocks in the midst of the 

 boiling surf during their lifetime. 



To describe the forms of these beautiful little flesh-spi- 

 cules in detail, in a general introduction to the classifica- 

 tion of the Spongida, would be out of place ; and there- 

 fore the student must seek for this in the description of the 

 sponges respectively to which they belong, while now they can 

 be only noticed in a general way ; and as with the " skeleton- 

 spicules," so here, it seems best to give a Table of the com- 

 monest known forms which the flesh-spicule may assume, that 

 the student may to a certain extent become acquainted with 

 them, and thus prepared to describe others which he may 

 afterwards discover. Descriptions, however, at best are very 

 inadequate to the purpose ; and therefore I hope to add here- 

 after tabular delineations of both the skeleton- and the flesh- 

 spicules, as before stated. 



