ITS STOPPER. 291 



power of expanding into a cone, if it should ever be 

 needed by the accidental loss of the fellow now so fur- 

 nished. I thus judge, because experience shows me 

 that the conical club is occasionally thrown off, and 

 quickly renewed, in captivity. 



My esteemed friend, the Eev. Sir Christopher Lighten, 

 has indeed put on record an example of a Serpula of 

 this species possessing two equal antenna?, that had 

 replaced the single one accidentally lost. They were 

 both perfectly developed, and joined together near the 

 base. Each was decidedly smaller than the single one 

 that had formerly occupied their place. 1 This exceed- 

 ingly interesting case can, of course, only be regarded 

 as a monstrosity of redundancy, as children are some- 

 times born with a superfluous finger. But it is valuable 

 as showing that there is a power of development latent 

 in the crownless antenna. I wish very much that the 

 excellent observer had added a note, telling us to what 

 extent the tube was closed, and how the work was per- 

 formed without mutual interference. 



It has been sometimes brought as an objection to 

 our assigning a certain service to certain organs, that 

 the necessity for such service is a gratuitous supposi- 

 tion, since other creatures similarly formed in most 

 respects, and in which we might infer a like need, have 



1 Zoologist, p. 5976. 



