260 STTJD^ OF THE CEPHALIC DISK OF THE REMORA. 



7. The tranformatioD of potential energy into muscular power is 

 neccesarily accompanied by the production of heat within the body, 

 even when the muscular power is exerted externally. This is, doubt- 

 less, the chief and, probably, the only source of animal heat. 



[E. F.] 



A STUDY OF THE CEPHALIC DISK OF THE REMORA. [ECHENEIS.] 

 From the " Comptes RenduesJ' 



Abstract by the author of a memoir by M . B. Bandelet, presented to the 

 Academy by M. E. Blanchard. 



The disk ou the head of the Remora has been, from the most remote times, an 

 object of interest to observers. Among modern Naturalists, some, as Voigt, 

 and Stannius, have advanced the opinion that the disk may be regarded as the 

 equivalent of a dorsal fin ; but this mode of viewing the subject has not been 

 supported by a rigorous demonstration, since there are certain interior portions 

 of the disk whose relations have not been determined ; moreover the mechanism 

 by means of which the attachment of the disk is accomplished, has not yet been 

 analyzed and explained in a satisfactory manner. The researches which I have 

 the honor to submit to the Academy, have for their object the solution of these 

 still obscure problems. The disk of the Remoras occupies, as is well known, the 

 upper surface of the head. Its figure is that of a much elongated oval, of which 

 the border, a little elevated, consists of a fold of the skin so disposed as to form 

 around the organ a sort of flexible case. The upper surface of the disk is level, 

 it presents on each side of the median line, a series of little transverse laminse, 

 nearly parallel, and slightly inclined backward, so as partly to cover each other 

 like the laths of a Venetian blind. Between these folds are as many corresponding 

 empty spaces. 



Excepting the border, the disk is supported by an internal frame-work formed 

 by a considerable number of small bones, disposed in a series of similar segments 

 regularly succeeding one another from behind forward. Each segment consists 

 of the following pieces, four in number : one interspinal bone, two radial bones, 

 and an articular bong element. 



The interspinal bone is a small unpaired piece, occupying the median line on 

 the lower face of the disk, of ihe form of a sharp spine with its point downwardsi 

 its aspect in every respect bringing to our minds the interspinal bones which 

 support the rays of the fins ; it is of the same nature with them. 



The rays are represented by two little bony stems set across in a horizontal 

 plane and articulated at their base on the level of the median line, with the cor- 

 responding interspinal bone. Each of these stems, taken alone, corresponds 

 with a half-ray of a fin, this half, instead of remaining closely attached to its 

 fellow in a vertical plane, being withdrawn from it so as to lie down sideways. 



The articular bone element is an unpaired, symmetrical bone, extended across 

 the disk, of which it occupies the whole width. It consists of a very narrow 

 middle portion, and of two lateral portions, enlarged into laminae, or quadrilat- 

 eral plates. From the upper surface of these latter, protrudes a little lamellose 



