44 



of a distinct polyp. The Sponge, on the other hand, was an indi- 

 vidual. The well-known article of commerce was only its skeleton. 

 Over this porous skeleton was spread the living animal, a homo- 

 genous mass of sarcode. This sarcode was a soft, gelatinous, flesh- 

 like substance. Over this is a thin membrane or envelope, in which 

 the pores exist. Entering into the sarcode and skeleton were 

 numerous siliceous or calcareous spiculse. The whole, in its adult 

 state, was attached by a root, presenting that fungoid appearance 

 which had caused it to be ranked among the Zoophytes. The 

 skeleton seemed to be secreted by the animal in a manner similar 

 to the shells of Mollusca. It consisted generally of a fibrous, 

 horny substance, which had obtained the name of Jceratode. This 

 varied, however, in character in different species. Some secreted 

 carbonate of lime, some silica, and some keratode. The spiculse 

 were either siliceous or calcareous. The skeleton was only de- 

 veloped in the adult stage. The sarcode, or animal itself, according 

 to Dr. Bowerbank, was nearly on a level with the most vital parts 

 of the most highly developed organisms. It had a species of loco- 

 motive power, but no apparent organs for any specific purpose. It 

 seemed simply a mass of cellular tissue, with no nervous or vascular 

 system ; yet it performed several vital functions, such as motion, 

 inhalation, nutrition, and reproduction. It imbibed its food by 

 simple contact. The water, moved by cilia, situated around and 

 within the orifices of the pores, was inhaled, bringing the food 

 along with it, and exhaled by other and larger apertures called 

 oscula, bearing away the excretions. These latter orifices were 

 also the seat of reproduction, the gemmules of the new animals 

 issuing therefrom. The spiculse seemed to be used for various 

 purposes — sometimes for defence, at other times for seizing its 

 prey. Another, and perhaps chief use, was for strengthening of 

 the skeleton. 



The lecturer exhibited a number of the skeletons of Sponges : 

 amongst others, a beautiful siliceous one, belonging to the Museum, 

 The latter specimen belongs to a class commonly called the " glass 

 sponges," scientifically named " Euplectella," until lately but little 

 known, and exceedingly rare. The long filaments of these Sponges 

 exactly resemble fine-spun glass. Another rare species was noticed 



