123 



received into the mouth, which is of small size and not distensible like that 



of the ASTEROIDA."* 



Farther on Dr. Carpenter says : 



" It was affirmed by M. Dujardin (I'lnstitut, No. 119, p. 268) that 

 the arms are used for the acquisition of food in a manner altogether dissi- 

 milar to ordinary prehension ; for recognizing the fact that the alimentary 

 particles must be of small size, he supposed that any such, falling on 

 the ambulacral (?) furrows of the arms or pinnse, are transmitted down- 

 wards along those furrows to the mouth wherein they all terminate, by 

 the mechanical action of the digitate papillae which fringe their borders. 

 This doctrine he appears to have abandoned ; since in his last account of 

 this type (Hist* Nat. des Echinoderms, p. 194) he affirms that the trans- 

 mission of alimentary particles along the ambulacral (?) furrows is the 

 result of the action of cilia with which their surface is clotted. Although 

 I have not myself succeeded in distinguishing cilia on the surface which 

 forms the floor of these furrows, yet I have distinctly seen such a rapid 

 passage of minute particles along their groove as I could not account for 

 in any other mode, and am therefore disposed to believe in their existence. 

 Such a xmverfal indrauglitj moreover j must he produced about the region 

 of the mouthy hj the action of the large cilia ivhich (as I shall hereafter 

 describe) fringe various jjarts of the internal tvall of the alimentary 

 canalj as would materially aid in the transmission of mimde particles 

 cdong those x)ortions of the ccmhulacral (f) furroivs ivhich immediately 

 lead toivard it / and it is, I feel satisfied, by the conjoint agency of these 

 two moving powers that the alimentation of Antedon is ordinarily effected. 

 In the very numerous specimens from Arran the contents of whose 

 digestive cavity I have examined, I have never found any other than 

 microscopic organisms ; and the abundance of the horny rays Peridiinum 

 tripos (Ehr.) has made it evident that in this locality that Infusorium 

 was one of the principal articles of its food. But in Antedons from other 

 localities, I have found a more miscellaneous assemblage of alimentary 

 particles ; the most common recognizable forms being the horny casings of 

 Entomostraca or of the larvae of higher Crustacea." (Op. cit., p. 700 



The existence of large cilia within the intestinal canal, capable of 

 producing a powerful indraught of water, renders any movement or 

 concurrent action of the arms quite unnecessary in the ingestion of food. 

 It does not matter, therefore, in what part of the body the mouth of a 

 Crinoid may be situated, or how remote from the reach of the arms.? 



* Researches on the Structure, Physiology, and Development of Antedon {Comatula 

 Lamk.) ro!sacem.—Va.ii I. By W. B. Carpenter, M.D., F.R.S. Philosophical Transactions 

 of the Royal Society, vol. clvi, Part 11., 18G6. 



