124 



Attached permanently to the bottom of the sea by their columns, the 

 palaeozoic Crinoidea, Cystidea and Blastoidea 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 be, from time to time, thrown out through the mouth, just 

 as a Star-fish or a Zoophyte frees itself of the refuse portions of its 

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



10. On the Theory that the amlmlacral and ovarian orifices are the oral 



apertures. 



Assuming that the four objections above noticed are sufficient to prove 

 that the aperture which I call the mouth is not that organ, it is contended 

 that the Cystidea, Blastoidea and Palaeocrinoidea ingested their food 

 through their ambulacral and ovarian orifices. This appears to me in the 

 highest degree improbable. In the recent Crinoids the grooves of the 

 arms are occupied by four sets of tubes, which Dr. Carpenter calls the 

 coeliac, the sub-tentacular, the ovarian and the tentacular canals. None 

 of them communicate with the stomach. It is impossible that the most 

 minute particle of food could gain access into the interior of the animal 

 through any of them. The structure of the arms of the palaeozoic Crinoids 

 is such, that we must presume that their grooves were occupied by similar 

 tubes, which passed through the ambulacral orifices into the perivisceral 

 space. In the Cystidea and Blastoidea the respiratory organs were not 

 situated in the grooves of the arms, and the ambulacral orifices were 

 therefore only ovarian in their function. The improbabihty of their being 

 also oral apertures is best shown by an illustration. 



In fig. 84, is represented (natural size) the apertures of the smallest 

 Fig. 83 Fig. 84. specimen of Caryocrinus ornatiis, in our collection 



selected for the present purpose because in the young 

 of this species, the valvular orifice is larger in pro- 

 portion to the size of the disc, than it is in the adult. 

 It is in this specimen, about one-third of the whole width of the apical 

 disc, while in a full grown Caryocrinus it is only one-ninth of the 

 width. The same proportional size of the mouth according to age, occurs in 

 Antedon rosaceus. The valvular mouth at first is as wide as the disc. 

 But as the age of the animal increases the disc grows wider, but the mouth 

 does not. The ovarian pores in Caryocrinus are, however, as large in the 

 small ones (once they make their appearance) as they are in full grown. 



