380 THE AMERICAN MONTHLY [Dec. 



cases the cellular aggregate is supported by a framework 

 of horny fibres, or of flinty or calcareous spicules. A 

 definite mouth and stomach are wanting, and a nervous 

 system is not known with certainty to be developed." 

 The water which takes the food into the sponge goes in 

 by the "pores " which occur all over the organism. Here 

 it is passed into the " inhalent " canals. These conduct 

 to the "ciliated chambers" which go to the " exhalent 

 canals" and into the cavity which is in the center of the 

 sponge. Hero it is voided by a larger opening at the 

 top which is known as an " Oscula." This is the 

 typical sponge. The oscula, though capable of being 

 temporarily closed, are permanent, and are often placed 

 on chimney-like elevations. What is commonly called a 

 " sponge " may consist of only a single excretory opening or 

 "oscula," together wdth the "pores" belonging to this ; 

 or it may consist of a larger or smaller number of such 

 " oseula." each with its proper complement of " pores." 

 In the latter case, each oscula, with it accompanying 

 pores, constitutes a "person," and the entire organism is 

 known as a "sponge stock." 



There are a few sponges of which no skeleton of the above 

 description can be found, these are knoAvn to science as 

 the Myxospongij^e. In the vast majority the. soft cellular 

 body is supported by more or less extensively developed 

 hard structures ; which collectively constitute the 

 skeleton. There are four types of the skeleton. First, in 

 certain sponges (such as the common bath sponges) the 

 skeleton is composed of netted horny fibres, without the 

 proper " spicules." The substance composing the fibres 

 in such types is allied to horn, but not precisely of the 

 same nature, and it is known as " spongian " or " Kena- 

 tose." Such sponges can be mounted very easily, only 

 washing them in alcohol, or rather a small piece, and 

 transferring it to a solution of gum thus. The prepar- 

 ation shows nicely. 



