254 Dr. T. Williams on the Mechanism of Aquatic 



Intervectal and Interlamellar Framework of Connective 

 Structures. 

 These structures constitute the true skeleton by which is 

 sustained the vascular fabric of the gill. Of the latter, they 

 determine the shape and the form. They preserve the blood- 

 carrying bars in position. They hold apart the component 

 lamellae of the gills. They thus form the interlamellar tubes, since 

 without these structures the lamellae would fall together into 

 contact and obliterate the tubes. Messrs. Alder and Hancock 

 recognized the tubes, but overlooked the framework system by 

 which they were constructed *. M. Deshayes has figured this 

 framework (PI. VI. fig. 1 c,c,c & d, fig. 2 i, and fig. 8 d, d) ap- 

 paratus in a conchiferous (Pecten or Area ?) mollusk. Not a 

 sentence is written descriptive of its characters, or interpretative 

 of its meaning f. Attention was drawn to it by no allusion 

 whatever, direct or incidental. PhilippiJ has this observation 

 with respect to the branchiae of Solenomya, which probably 

 refers to the interlamellar structures in question : — " Branchiae 

 duo non quatuor, non lamelliformes, seel pectinatse vel potius 

 pennam exacte referentes, lamellis transversis perpendicularibus, 

 carina media corpori per totam longitudinem adnata?, versus 

 apicem ope ligamenti." Ill-defined reference to the same parts 

 is made by Carus, Blainville, Garner, and others. To be 

 known descriptively, and comprehended physiologically, they re- 

 mained really to be rediscovered, — to be read by a new eye, from 



* It is very probable, from the following passage, that Messrs. Alder 

 and Hancock have mistaken the thick solid cords which at short intervals 

 cross the tubes, for real blood-channels : " The laminae forming the walls 

 of these tubes were now examined through the microscope, when the whole 

 was observed to present a regularly reticulated structure composed of 

 blood-vessels; those passing transversely being the stronger and more pro- 

 minent ."—Annals and Magazine of Natural Historv, paper on Currents 

 in Pholas and Mya," 1852. 



t The following is the only passage which occurs iu the excellent 

 article (Conchifera, Cyclop. Anat. Phys.) of M. Deshayes having reference 

 to the structure of the gills : — " In the greater number of genera, the 

 branchiae are formed of two membranous layers or laminae (a, b, fig. 352), 

 within the substance of which the branchial vessels descend with great 

 regularity. In several genera, as the Archidce and Pecte?i, the branchial 

 vessels, instead of being connected parallel to one another within the 

 thickness of a common membrane, continue unconnected their entire length, 

 and they are thus formed of a great number of extremely delicate filaments, 

 attached by the base within the membranous pedicle on which the bran- 

 chial veins pursue their way towards the auricle." Nothing is said of the 

 distinct and independent structures which separate the laminae. The con- 

 dition, namely the separation of the laminae — upon which depends the 

 existence of the interlamellar water-tubes — is here accidentally stated ; but 

 neither the existence nor the meaning of such parts seem in the slightest 

 degree to have been imagined by M. Deshaves. 



X Moll. Sicil. i. p. 16. 



