358 LECTURE XXIV. 



added ventricles. With this mechanism for the vigorous propulsion 

 of the venous blood through the oxygenating organs, they acquire, 

 in the Dibranchiate Cephalopods, a perfection of structure unknown 

 in the rest of the Invertebrata, but always present in the Vertebrated 

 classes. 



The male Dibranchiafa are always fewer, and generally smaller, 

 than the females ; the latter sex alone has hitherto been recognised 

 in the genus Argonauta., and some suspect the brachial membranes 

 and the shell to be sexual distinctions. In the common Loligo, the 

 gladius of the male is one fourth shorter, but is broader than that of 

 the female. 



The male organs consist of a testis, a vas deferens, a vesicula 

 seminalis, a prostate, the sac of the spermatophora, and the penis. 



The testis is situated in a particular compartment of the peritoneum 

 at the bottom of the visceral cavity : it consists of a membranous 

 pouch, to one part of the inner surface of which are attached a 

 number of slender branched tubuli, diverging, dichotomising, and 

 terminating in blind extremities: the tubuli swell at the breeding 

 season, burst, and discharge an opaque white fluid, crowded with 

 spermatozoa, into the cavity of the sac, whence it escapes by a con- 

 tracted orifice into the slender and convoluted vas deferens, where 

 the fluid is moulded, by the addition of a mucous secretion, into a 

 cylindrical coherent mass. In this state it is transmitted to a wider 

 glandular canal, with fibrous parietes and a cellular cavity in the 

 Octopus, and enci'oached upon, in the Sepia, by a plicated production 

 of the lining membrane : this division of the eff"erent part of the 

 male apparatus is analogous to the glandular part of the oviduct in 

 the female : here the spermatozoa are enclosed in filamentary sheaths 

 of albuminous matter, of a definite form, according to the species of 

 Cephalopod. The anterior extremity of this contractile vesicula com- 

 municates, in the Octopus, with a wide, bent, csecal tube (prostate), 

 with thick glandular parietes, and having the form of a simple pouch in 

 the Sepia, from which a short and wide duct leads to a longer and 

 larger pyriform pouch, with thinner walls, containing the moving 

 filaments of Needham, and from which the short muscular penis is 

 continued. The prostate, in the Sepiola, communicates by a long 

 and slender duct with the vesicula seminalis. 



The moving filaments in the terminal pouch are packets or 

 capsules of spermatozoa and sperm-fluid, with a peculiar associated 

 mechanism. They form one of the most remarkable peculiarities of 

 the Cephalopoda, and have been regarded as parasitic worms, under 

 the names of Echinorlnjnclms, Scolex dibothrius, Needhamia expul- 

 satoria, &c., by diflferent comparative physiologists : they have been 

 aptly denominated ' spermatophora' by Dr. Milne Edwards. 



