788 MECHANISM OF RESPIRATION, ETC. 



Valenciennes in the female, and I have not been fortunate enough to find a fecundated 

 female among my preserved specimens'. 



I have often taken males which had discharged the spermatophore, the empty and 

 ruptured cyst remaining behind in its usual position in the fossa buccalis. In captivity 

 the males sometimes become sperm-bound, that is over-mature, the spadix presenting 

 a congested appearance and the penial lumen and Needhamian sac turgid with sperma- 

 tophores, death resulting. 



12. Mechanism of Respiration ; Branchiae and Osphradia ; Renal and 



Pericardial Follicles. 



The pallial insertion of the gills of Nautilus has been already referred to. They 

 are planted upon the mantle by means of a thick, fleshy peduncle which serves as 

 a massive buttress at the back of each gill, i.e. on the venous side of the gill 

 (PI. LXXXII. fig. 8). The inner surface of the gill, that is to say, the side which is 

 turned towards the middle line of the body, is the arterial surface, and the vessel 

 which lies below this surface leads directly into the corresponding hranchio-cardiac or 

 efferent branchial trunk. The outer surface, which is supported by the above-mentioned 

 buttress at the base of the gill, is the venous surface, and the vessel which lies below 

 the integument on this side is the continuation of the con-esponding reno-hranchial or 

 afferent branchial vessel which arises from the sinus venosus. 



In Nautilus as in other Cephalopoda, and moreover as in the Diotocardia {Huliotis, 

 Pleurotomaria, etc.) and in the Acephala, the renal apparatus is intercalated into the 

 branchial circulation. 



The structure of the gill of Nautilus strongly resembles that of the gill of the 

 Gastropoda, Prosobranchia, Diotocardia, Aspidobranchia. It consists of an axis or stem 

 bearing a double series of alternating branchial fulia or gill-plates, and only differs in 

 details from the gills of other Cephalopoda-. Especially does it agree with the latter, 

 and diverge from the prosobranchiate gill in the absence of cilia from the branchial 

 epithelium^ The stem of the gill of Nautilus arises by a broad but simple peduncle 

 from the inner surface of the mantle not far from the angle of insertion of the mantle 

 into the body-wall, and it undergoes no secondary concrescence either with the mantle 

 or with the body-wall, being free from base to apex. Each branchial lamella is at- 

 tached to the stem by means of a supporting membrane which presents a free border 

 on the dorsal (venous) side of the gill. The free borders of the basilar membranes of 



' A spermatophore released from its ej-st and adhering to the organ of Valenciennes was first figured 

 by Mr Graham Kerr [op. cit. 189.5). Another instance has quite recently been recorded by Mr L. E. GrilBn 

 in a work which was received at the British Museum too late for extended and critical notice here. 

 Griffin, L. E., " The Anatomy of Nautilus pompilius," Mem. Ac, Washington, Vol. viii. fifth memoir, pp. 

 103 — 197, 11 text-figg. 17 plates, dated 1898 on cover, 1900 on title-page, received at the British (Natural 

 History) Museum on March '21th, 1902. 



'^ Cf. Joubin, L., " Structure et developpement de la branehie de quelques Cephalopodes des cotes de 

 France." Arch. Zool. Exper. (2) in. 1885, pp. 75—150, PI. iv.— vi. 



^ In Haliotis for example the whole surface of the branchial lamellae is ciliated (Wegmann, Arch. Zool. 

 Exper. (2) ii. 1884, p. 316). The gill-primordia are ciliated in Loligo according to Brooks {Anniv. Mem. 

 Boston Soc. Nat. Hist. 1880), but not in Sepia according to KoUiker {Entwick. d. Cephalopoden, 1844, p. 54). 



