228 ANATOMY AND PHYSIOLOGY 



TERMINOLOGY, 



AND DESCRIPTIONS OF THE ILLUSTRATIVE FIGURES. 



Professor Ehrenberg in the course of his laborious and 

 valuable researches into the nature of the various minute 

 organized bodies contained in the earths of recent and 

 ancient geological deposits, has described a large number 

 of sponge spicula, which he has named and arranged in 

 genera and species in accordance with their forms ; but as in 

 many species of existing sponges we find three or four of 

 his genera and species of spicula, and in other cases we 

 find one of his species common to a dozen or more distinct 

 genera and species of recent sponges, it becomes impossi- 

 ble systematically to apply the names he has given to these 

 organs to the descriptions of the living species of Spongiadae 

 with any degree of propriety or certainty. I have there- 

 fore been compelled, in constructing a terminology for the 

 description of the Spongiadae, to consider the names 

 applied to those organs by my learned and highly esteemed 

 friend, Professor Ehrenberg, as provisional terms rather 

 than as permanent denominations, and to designate the 

 numerous and varied forms of these organs in such a 

 manner as to render their names as closely descriptive of 

 their forms as possible, after the manner in which the 

 nomenclature of botanical organs has been treated by the 

 best writers on that science. 



The quantity of new names, and of figures illustrative of 

 them, is necessarily large, and to facilitate the references 

 from the one to the other I have numbered the figures as 

 a continuous series, and not with reference to each sepa- 

 rate plate ; and the descriptions of the illustrations are 

 numbered to correspond with the figures appended to 

 them, so as to render the references mutual ; and the same 

 system of reference is applied throughout the work, each 

 number leading the student to both figure and description. 



