34 STRUCTURE OF THE CYSTIDE.^. 



be designed for such very different purposes as would result from the adoption of the 

 opinion of L. von Buch, on the one hand, relative to the use of the triangular plates 

 of the Cystide.T, and, on the other, from the direct observations made by Dr. Duchas- 

 saing." 



From the above remarks, it is evident that MM. Koiiinck and Le 

 Hon, vi^ho have profoundly studied the Crinoideas, are of opinion that 

 the ovarian pyramid of the Cystideag is the exact homologue of the 

 buccal apparatus of Ppntacrimis, a view in the correctness of wliich I 

 entirely concur. The only difference is that in PenUicrinus the anibu- 

 lacral orifice with its grooves is combined with the mouth and its 

 pyramid of valves, while in the Cystidepe they are separate. Von 

 Buch was of the opinion that the five valves of the Cystidcce were 

 perforated by five minute pores which were the ovarian pores. The 

 organ would then present a greater resemblance to the ordinary 

 arrangement of the reproductive system in the Echinodermata. In 

 most of the families of this class when the ovaries are contained in the 

 visceral cavity, there are many of them, and they have their orifices 

 disposed according to the radiated division of the body. Thus in the 

 Echinidae there are five ovarian pores, sometimes it is true, reduced 

 to four in the abnormal forms ; in the Blastoidea there are five, in 

 the Ophiurida? ten, and in many of the Star-fishes five or ten.* 

 It is thus contrary to analogy that when an Echinoderm has the 

 reproductive system included in the cavity of the body, there should 

 be but one genital opening. 



4. If we consider the relative dimensions of the several apertures, 

 we find that in general the mouth is larger than the anus. 

 Although in the fossil Echinidae the anal aperture often appears 

 to be as large as the oral, yet this is owing to the destruction of a 

 portion of it. In the living specimens the opening is covered over 

 with the exception of a mere pore, while the mouth is of a large 

 size. In the Star-fishes, wherever an anus exists it is always many 

 times smaller than the mouth. In Ghjptocystitcs 7nvIfij)orus the apical 

 aperture is only one-tenth the size of the lateral opening; in 

 Malocystites Murchisoni one-ninth ; in Echino-encrinites angulosus one- 

 ninth ; in Hemicosmites pyriformis it consists of a minute three-rayed 

 fissure (see the beautiful figure in plate iv. fig. 5, Milller, Ubcr den 

 Bau der Echinodermm) ; in all the species of Pleurocystites, although 

 it has not been observed, yet the structure of the parts proves that 



* See the figures of the genital pores of Asteracanthion rubens and Solaster papposus, 

 Plate xii. System der jlsteridrv, von Miiller und Troscbel. 



