40 STRUCTURE OF THE CYSTIDE^. 



absence of any aperture corresponding with them. The Cijstidece, on 

 the other hand, have at least two and sometimes three apertures to 

 their calyx, one of which, distinguished by its valvular closure, is found 

 m no other Crinoids than the Cystideod. L. von Buch has determined 

 that this valvular pyramid is the genital aperture.* We owe to him 

 the recognition of the close alliance of these forms with the Crinoids, 

 and at the same time of their peculiarities, the exact analysis of their 

 calyces, and the exposition of their genera. That they are not armless, 

 as had hitherto been generally supposed, was first observed by A. 

 von Volborth, who discovered the arms in Eclnno-cncrinus angulosus 

 and striatus, subsequently in Echinosphcer'ilcs aurantium, where they 

 proceed from the mouth. The figures of the Duke of Leuchtenberg, 

 and those of Volborth of Sphcero/ntcs Leuchtenhergii and Protocr'mites 

 oviformis would indicate the piesence of arms in these also, although 

 they have not been actually obtained. In fact, branched grooves 

 run from the mouth over a great part of the calyx ; the branches of 

 the grooves however end in papillae of the calyx, which must be 

 regarded as points of origin of arms — a circumstance so much the 

 more remarkable, as it would follow that the arms of these Cystidew 

 must have had a position far removed from the mouth (Verhandl. d. 

 Konigl. Mineralog. Gesellschaft zu Petersburg, 1845-6, Petersb. 1849). 

 A specimen of SpJuironitcs Leuchtenhergii in von Buch's collection 

 agrees exactly with these figures. When, in his second essay, L. von 

 Buch founded the order Cystidea (1844), the oral arms of Echhio- 

 encriniis were already known. He did not regard them as Crinoid 

 arms, but called them feelers. With a correct foresight he even then 

 arranged the Pseudocrinites and Agelocrinus, with long arms passing 

 from the oral part of the calyx, among the Cystidea, but was not 

 Hiclined to consider these processes as true arms. He had even in 

 1840 termed the remains of the three arm-like processes in Hemiscosmites 

 arms or proboscidcs, Imt was led away from a just comprehension of 

 their nature by comparing them with oral tubes. 



"In his beautiful monograph on the British Cystideans (Mem. 

 Greol. Survey, t. ii. Lond. 1848) Forbes has increased the number 

 of forms with oral arms. He divides the CystidccB into, — 1st, those 

 with arms: Pseudocrinites., Apiocystiles, Agelocrinites — 2nd, those with 



* In my copy of Miiller, " Uber den Bau der Bchinodermen," the following sentence 

 follows here : — " Eine Vermuthung, die freilich nicht sicker bcweisen werdeii konntc,'' 

 which may be thus rendered : " -'.n opinion which surely cannot be positiiiely proved." 

 Miiller appears therefore to have believed that Von Buch's demonstration was not 

 complete. 



