1870.] BILLINGS — ON CRINOIDEA AND BLASTOIDEA. 195 



am therefore disposed to believe in their existence. SucJi a power- 

 ful indraughtf moreover, must he produced about the region of tJie 

 mouth, hi/ the action of the large cilia tuhich (^as I shall hereafter 

 descrihe^ fringe various parts of the internal loall of the alimen- 

 tary canal, as loould materially aid in the transmission of minute 

 particles along those portions of the amhulacral (^?) furrows which 

 immediately lead torward it ; and it is, I feel satisfied, by the 

 conjoint agency of these two moving powers that the alimentation 

 of Antedon is ordinarily affected. In the very numerous speci- 

 mens from Arran the contents of whose digestive cavity I have 

 examined, I have never found any other than microscopic organ- 

 isms; and the abundance of the horny rays, Peridinium tripos, 

 (Ehr.) has made it evident that in this locality that Infuso- 

 rian was one of the principle articles of its food. But in Ante- 

 dons from other localities, I have found a more miscellaneous 

 assemblage of alimentary particles ; the most common recogniz- 

 able 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 move- 

 ment 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. Attached permanently to the bottom 

 of the sea by their columns, the Crinoidea, Cystidea and Blast- 

 oidea remained, while feeding, most probably motionless, drawing 

 in streams of water through their mouths by the action of their 

 intestinal cilia. The long tubular proboscis with which many of 

 the species are provided, would be, thus, analogous in function to 

 the siphon of the acephalous mollusca. The indigestible particles 

 would le, from time to time, thrown out the mouth, just as a 

 Star-fish or a Zoophyte frees itself of the refuse portion of food, 

 by casting it out of the same aperture through which it entered. 



10. On the theory that the ambulacral and ovarian 

 orifices are the oral apertures. 



Assuming that the four objections above noticed are suflBcIent 

 to prove that the aperture which I call the mouth is not that 

 organ, it is contended that the Cystidea, Blastoidea and Palseocrin- 

 idea ingested their food through their ambulacral and ovarian 



