SPONGES. 



149 



sents to the eye two- kinds of orifices ; the larger 

 having a rounded shape, and generally raised 



55 



margins, which form projecting papillae ; the 

 smaller being much more numerous, and ex- 

 ceedingly minute, and constituting what are 

 termed the pores of the sponge. 



It has, for a long time, been the received 

 opinion among naturalists that this supei'ficial 

 layer of gelatinous substance was endowed with 

 a considerable power of contractility : it was 

 generally believed that it shrunk from the touch, 

 and that visible tremulous motions could be ex- 

 cited in it by punctures with sharp instruments, 

 or other modes of irritation. It is extraordinary 

 that errors like these should have crept into the 

 writings of modern zoologists of tlie highest 

 authority, such as Lamarck, Bruguiere, Gmelin, 

 Bosc, and Lamouroux.* The notion that the 



* This mistaken view was adopted by Cuvier in the first edition 

 of his " Regne Animal," T. iv. p. 88. ; but Dr. Grant's rectifica- 

 tion of the error is noticed iti the second edition of that work. — 

 T. iii. p. 322. 



