the Crinoidea, Cystidea, and Blastoidea. 157 



jmeustes drobachiensisj Ag., natural size and arrangement. It 

 may not appear at first view that this hitter comparison has 

 any probative effect. But it has, in this way. If these aper- 

 tures in Cari/otrimis were large openings a line wide, as are 

 some of the ambulacral orifices of the Crinoids, I should say 

 that they were unlike true ovarian apertures. 



According to the new theory, this Echinoderm, Canjocrinus 

 ornatus, was a polystome animal, and drew in its food through 

 its six ovarian apertures, the large valvular orifice being the 

 anus. To me this appears to be utterly incredible. 



In fig. 14 I have represented the mouth of Leskia niirahilis, 

 Gray. Both Dr. J. E. Gray and Prof. Lovdn have pronounced 

 this aperture to have the structure of the valvular orifice of 

 the Oystidea. I have not the slightest doubt whatever that 

 the mouth of the Cystideans foreshadows that of the sea- 

 urchins. There is nothing whatever in its structure to show 

 that it is n(Tt the mouth, but the contrary. 



The new theory is not founded upon any peculiarities in the 

 structure of the ambulacral orifices wbich would show that 

 they are oral a])ertures, but only upon the four objections 

 above noticed. The first of these is not logical, while at the 

 same time it is purely theoretical, and avails nothing against 

 material and visible facts. The fourth is completely disposed 

 of by Dr. Carpenter's observations, which prove that in the 

 Crinoidea the arms have no share whatever in the ingestion of 

 food. The second and third objections are the same in sub- 

 stance ; I. e. according to the second the supply of water to the 

 mouth is diminished by the occurrence of a Platyceras over it, 

 while, according to the third, the same effect is produced by 

 the small size of the aperture itself in some instances. It does 

 not require much consideration to convince one that, if these 

 two objections are fatal to my views, they are equally so to 

 the opposite theory. In C. steUiformis^ for instance, the pores 

 through which we must suppose the ovarian tubes issued from 

 the interior are only large enough to admit of the passage of a 

 fine hair ; they are scarcely visible to the naked eye. The 

 tube, under any circiunstances, must have filled them almost 

 entirely. If any space at all were left for the passage of a 

 stream of water through the pore by the side of the tube, it 

 must have been exceedingly minute. 



AVhen weighed as above, therefore, the evidence gives the 

 following results : — The first and fourth objections avail no- 

 thing ; the second and third militate against both theories ; 

 but when we take into account that in no instance, in the 

 existing Echinodermata, where ovarian pores occm', are they 

 at the same time oral orifices, the balance seems to be in favour 



