OBJECTIONS TO THE THEORY 325 



have been beneficial without the freely movable stalk, 

 nor could the latter have been efficient without the snap- 

 ping jaws, jet no minute merely indefinite variations 

 could simultaneously evolve these complex co-ordinations 

 of structure; to deny this seems to do no less than to 

 affirm a startling paradox." Paradoxical as this may 

 appear to Mr. Mivart, tridactyle forcepses, immovably 

 fixed at the base, but capable of a snapping action, 

 certainly exist on some star-fishes; and this is intel- 

 ligible if they serve, at least in part, as a means of 

 defence. Mr. Agassiz, to whose great kindness I am 

 indebted for much information on the subject, informs 

 me that there are other star-fishes, in which one of the 

 three arms of the forceps is reduced to a support for the 

 other two; and again, other genera in which the third 

 arm is completely lost. In Echinoneus, the shell is de- 

 scribed by M. Perrier as bearing two kinds of pedicel- 

 lariae, one resembling those of Echinus, and the other 

 those of Spatangus; and such cases are always interest- 

 ing as aft'ording the means of apparently sudden tran- 

 sitions, through the abortion of one of the two states 

 of an organ. 



With respect to the steps by which these curious 

 organs have been evolved, Mr. Agassiz infers, from his 

 own researches and those of Miiller, that both in star- 

 fishes and sea-urchins the pedicellarise must undoubtedly 

 be looked at as modified spines. This may be inferred 

 from their manner of development in the individual, as 

 well as from a long and perfect series of gradations in 

 different species and genera, from simple granules to 

 ordinary spines, to perfect tridactyle pedicellariae. The 

 radation extends even to the manner in which ordinary 



