154 Mr. E. Billings un the Structure of 



scopic organisms. It is stated by Meek and Worthen that 

 wlici-e there is a proboscis the aperture is sometimes scarcely 

 " more than one hundredth of an inch in diameter." I believe 

 that in many such instances 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 

 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 also informed that in some of the existing species of 

 Antedon " the mouth is an exceedingly 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 justified in asserting that it is «of (as stated by several 

 authors whom I have eited in my historical summary ) tlie prehension 

 of food. I have continually watched the results of the contact of 

 small animals (as Annelids, or Eutomostracan and other small 

 Crustacea) with the arms, and have never yet seen the smallest 

 attempt on the part of the animal to seize them as prey. J\Ioreover 

 the tubular tentacula ^\iih which the arms are so abundantly fur- 

 nished have not in the slightest degree that adhesive power which 

 is possessed by the ' feet ' of the Echinida and Asteriada ; so that 

 they are quite incapable of assisting in the act of prehension, which 

 must bo accomplislu'd, if at all, either by the coiling-up of a single 

 arm, or by the folding-together of all the arms. Now I have never 

 seen sueh coiling-up of an arm as could bring an object that might 

 be included in it into the near neighbourhood 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 

 consentaneous closure of all the arms together upon it, must be far 

 too large to be received into the mouth, which is of small size, and 

 is not distensible like that of the Asteriada " *. 



* " Rosoarclies on the Structure, Physiology, and Development of 

 Antedon (Comatida,\j\\nk.) roMtceus.''' Part I. By W. P>. Carpenter, 

 M.D., F.R.S. (Philosophical Transactions of the lioval Societv, vol. clvi. 

 part '2, 18GG. p. 099. ) 



