686 DR. AV. B. CAEPENTER OX THE STRrCTUEE, PHYSIOLOGY, AND 



\Yhich the use of the microscope alone can determine : and among the excellent figures 

 by -which it is illustrated, are admirable sectional views of the structure of the visceral 

 disk, which much surpass those subsequently given by Professor Joii. Mullee. I shall 

 have frequent occasion to refer to Heusinger's memoir, when I come to describe the 

 digestive apparatus of Antedon. 



In 1834 M. DE Blainville published his 'Manuel d'Actinologie,' in which the rela- 

 tions of the Ceixoidea to the other members of the Order Stellerida are carefully 

 examined and set forth. He divides that Order into three Families, Asteridea, Astero- 

 pliydea, and Asterencrinidea ; and of the latter he says (p. 248), " C'est a I'interessante 

 decouverte faite par M. Thohpsox d'une tres-petite espece d'Encrine vivante, sur les cotes 

 d'Irlande, et a son Memoire a ce sujet, que nous devons la possibilite d'etablir et de 

 caractcriser cette famille d'une maniere convenable, en nous appuyant aussi sur le travail 

 ex professo de M. Miller sur les Encrinites fossiles." Further on he says of Mr. 

 Thompson's discovery (p. 256), that he " a detruit toute espece de doute sur la place des 

 Encrines wantes ou fossiles, et a demontre clairement la justesse de la maniere de voir 

 de IlosiNUS, adoptee par Guettard, Ellis, Parkixson, et M. Cuvier, centre celle de 

 LixxE, suivie par M. de L.uiarck. Une Encrine n'est pour ainsi dire qu'une Comatnle 

 renversee, en supposant meme que cette position ne soit pas egalement naturelle a 

 celle-ci, ce que je suis fortement porte a penser, et qui, an lieu de sc cramponner a I'aide 

 des rayons accessoires, est fixee par le prolongement de la partie centro-dorsale." He 

 divides his i'samS.y Asterencrinidea into two groups, the y>'fg and i\\Q Jixed; the only 

 representative of the first being Comafula, whilst in the second he includes all Miller's 

 genera of Crinoids, with the addition of the genus PJujtocrin us, which he created for the 

 reception of Mr. J. V. Thompson's Pentacriniis Uiiropceiis, regarding it (and with reason) 

 as not properly referable to the genus Pentacriniis. He enters at length into the struc- 

 ture of Comafula, the skeleton of which he describes correctly enough, whilst in regard 

 to its soft parts he falls into some remarkable errors. Thus he states that the furrow 

 which runs along the axis and the lateral pinnules of each arm is provided Avith " cirrhes 

 ventousaires," which serve to enable the animal to seize its prey ; the fact being that 

 these tentacula are not in any degree prehensile, and have no concern whatever in the 

 acquisition of food. Again, whilst correctly describing the mouth, he states that the 

 stomach has no second orifice, but terminates posteriorly in a blunt point ; and that 

 which L.\M-UlCK regarded as the mouth, and which English authors had rightly taken 

 for an anus, he affirms to have no connexion with the alimentary canal, but to be a pro- 

 longation from the " general cavity of the body," adding the suggestion that it may be 

 the rcspirvitory outlet, or may be subservient to the function of locomotion, or may be 

 the termination of the oviducal canal. On this point he confesses himself unable to 

 speak confidently, not having succeeded in discoAcring oAaries in the only individual 

 which he dissected ; but he surmises that in changing its 2)lace the animal may make 

 use of its " vessie abdominale," contracting it ujjon the water with which it had been 

 previously filled, after the manner of Cuttle-fish. He rightly stated that Comatnlce 



