and Physiology of the Spongida.. 13 



belonging to the skeleton, there are others as especially be- 

 longing to the sarcode or the soft parts, which will be described 

 in connexion with this portion of the sponge-structure, to 

 which they are so intimately attached that, when the sarcode 

 drops off the skeleton from putrefaction, they for the most 

 part go with it — thus still further reducing our means of 

 describing the entire sponge from the skeleton alone. 



As the known forms of the skeleton-spicules of sponges 

 are exceedingly numerous, it may fairly be inferred that with 

 the discovery of new species of sponges these forms will be 

 found to be almost infinite. At the same time, as they are of 

 much consequence in specific distinction, it becomes necessary 

 to adopt some classification of them whereby the memory may 

 not only be aided in this respect, but assistance may also be 

 given in describing new ones. 



Under these circumstances I have framed the following- 

 Table, in which the known forms of the skeleton-spicule 

 are divided into three groups, viz. linear, radiating, and 

 ramular, each of which is based upon a fundamental form out 

 of which its divisions, subdivisions, genera, and species may 

 be evolved. The fundamental forms will be found in the 

 woodcuts ; and their modifications, in accordance with the 

 text, will be delineated hereafter in separate Plates, when 

 the species are noticed to which they respectively belong. 



It has been already stated that the development of the 

 spicule commences in a granule or minute cell, which on 

 elongating would give the " linear group," or on immediately 

 radiating would give the " radiating group/' or, by elongating 

 first and then branching off radiatingly at one or both ends, 

 as the case might be, would give the " ramular group." 

 Thus the Table of Forms would be based not on mere arti- 

 ficial arrangement, but absolutely on the development of the 

 spicule. That it should be viewed as complete even up to the 

 forms with which we are already acquainted is by no means 

 wished ; but that provisionally it offers a beginning to what 

 must in this respect be ultimately accomplished is all that can 

 be expected. 



My kind friend the late Dr. J. E. Gray being well aware 

 of the importance of this subject in studying the Spongida, 

 communicated a valuable paper upon it ('Annals,' 1873, vol. xii. 

 p. 203), to which the reader is referred for the views he has 

 therein enunciated. 



