122 



A third objection is the small size of the aperture in some of the species. 

 In general, where there is no proboscis, the orifice is from one-twentieth 

 to one-tenth of an inch in diameter, quite sufficient for an animal that sub- 

 sists on microscopic organisms. It is stated by Meek and Worthen that 

 where there is a proboscis, the aperture is sometimes scarcely more than 

 one-hundredth of an inch in diameter." I believe that in many such in- 

 stances the tube filled up by calcareous deposits on its inside, and that when 

 entirely obstructed, either a new aperture opened out in the side of the 

 proboscis, or that the animal died. In Mr. Wachsmuth's collection, I 

 saw a specimen with a second aperture in process of formation. A ticket 

 was attached to it by him, giving this explanation. I am alsD informed 

 that in some of the existing species of Antedon " the mouth is an exceed- 

 ingly minute aperture." 



A fourth objection is that the aperture is so situated that the arms could 

 not have conveyed food to it. It is, however, proved by Dr. W. B. 

 Carpenter, that in the recent Crinoids the arms are not prehensile organs. 

 The animal while feeding remains motionless, attached by its dorsal cirrhi 

 to a stone, shell, or other object on the bottom. Its arms are either 

 stretched out to their full length, or more or less coiled up, but quite 

 immovable. As Dr. Carpenter's remarks have a very important bearing 

 upon the subject, I shall take the liberty of quoting the following : — 



^' Whatever may be the purpose of the habitual expansion of the arms, 

 I feel quite jastiQed that it is not (as stated by several authors whom I 

 have cited in my historical summary) the prehension of food. I have 

 continually watched the results of the contact of small animals (as 

 Annelids, or Entomostracans and other small Crustaceans with the 

 arms, and have never yet seen the smallest attempt on the part of the 

 animal to seize them as prey. Moreover, the tubular tentacula with 

 which the arms are so abundantly furnished, have not in the slightest de- 

 gree that adhesive power which is possessed by the " feet " of the 

 EcHiNiDEA and Astbriada ; so that they are quite incapable of assisting 

 in the act of prehension, which must be accomplished, if at all, either by 

 the coihng-up of a single arm, or by the folding-together of all the 

 arms. Now I have never seen such coiling-up of an arm as could 

 bring an object that might be included in it into the near neighborhood 

 of the mouth ; nor have I seen the contact of small animals with a single 

 arm produce any movement of other arms towards the spot, such as takes 

 place in the prehensile apparatus of other animals. Moreover, any object 

 that could be grasped either by the coiling of one arm, or by the consenta- 

 neous closure of all the arms together upon it must be far too large to be 



