AND THE MALES OF CERTAIN CEPHALOPODS. 14? 



with the same chroraatophora as those which are distributed 

 over the whole surface of the body, and that it has at its base a 

 little semilunar aperture similar to that which we have observed 

 in the sac of the arm. Upon opening the vesicle we find in its 

 interior the hectocotyliform arm coiled up spirally (PI. IV. fig. 7), 

 so that its acetabula are turned towards the centre ; the dorsal 

 face of the arm towards the periphery of the vesicle. This arm 

 had reached its full development in the individuals in question ; 

 but in these also the vesicle had attained its final stage of deve- 

 lopment, since it is much smaller in a specimen described by 

 M . Verany in his work already quoted. Whilst we were examining 

 the arm rolled up in its vesicle, another living individual placed 

 in sea-water unrolled little by little the arm concealed within 

 its vesicle. The arm passed out by its base, and whilst it kept 

 on unrolling, the vesicle was reversed by the same action, and 

 ended by becoming the sac which we have described upon the 

 dorsal surface of the arm. It will now be readily explicable 

 why this sac has its internal face lined by chromatophora similar 

 to those of the skin, the external surface of the vesicle havino* 

 become the internal face of the sac. We can now also account 

 for the fact, that in all the individuals we observed the hectoco- 

 tyliform arm was always twisted and rolled up at its extremity, 

 an arrangement which was a result of the spiral coil which it 

 had formed in the vesicle. 



We may be very concise in our description of the female or- 

 gans, which are constructed upon the same plan as in Argonauta 

 and Tremoctopus. The simple ovary surrounded by its capsule 

 is situate at the bottom of the intestinal sac, and communicates 

 with two very long and convoluted oviducts, which are folded 

 up upon the two sides of the ovary. There does not exist, as 

 in Tremoctopus violaceus, any decided glandular enlargement in 

 the course of the oviducts ; but in the sole female which we have 

 had an opportunity of examining, we found in the course of the 

 left oviduct two eggs of an oval form, which were still retained 

 in the oviduct, and which were evidently on their way out. The 

 two apertures of the oviducts are placed as in the two other 

 species of Octopods which have hectocotyline generation, (i.e. 

 Argonauta and Tremoctopus violaceus,) at the base of the branchiae; 

 the oviducts passing under the branchial arteries and veins to 



10* 



