EXTERNAL SHELL. 17 



To satisfy myself that the thin shell of the Argonaut is em- 

 ployed by the female merely as a receptacle in which to deposit 

 her eggs, I dissected a specimen of A. yondola,\\'ith an egg-mass 

 occupying the discoidal part of the shell and the posterior por- 

 tion of the roof. The eggs, very numerous, ovoid, pale yellow, 

 and semi-pellucid, are all united together by a delicate, glutinous, 

 transparent, filamentous web, which is attached to each ovum by 

 a slender tapering peduncle at the anterior extremity. The 

 entire egg-muss is suspended to the body- whorl of the spire at 

 its anterior part by means of a pencil of delicate glutinous 

 threads, which retain it in a proper position. 



The posterior globular part of the body of the female is in 

 close apposition to the mass of ova, and thus, like a strange 

 aquatic Mygale, or other spider, does this remarkable cephalopod 

 carry about her eggs in a light calcareous nest, which she lirmly 

 retains possession of by means of the broad, expanded, delicate 

 membranes of the posterior pair of tentacles. When 'disturbed 

 or captured, however, she loosens her hold, and, leaving her 

 cradle to its fate, swims about independent of her shell. There 

 is not. indeed, the slightest vestige of any muscular attachment. 

 In a specimen of A. gondola, the ovary was distended with ova, 

 but in a much less advanced stage of development than those 

 deposited in the shelly nidus. Some of these latter were suffi- 

 ciently matured to enable me to trace, under the microscope, the 

 early indications of the being of the Argonaut; and although the 

 progress was not followed very far, it was sufficient to ascertain 

 the similarity with the changes observed by Poli in the same 

 genus, with whose writings I afterwards compared my remarks ; 

 the only ditference of any importance appears to be that Poli 

 regarded :is the shell what I have called the yolk-bag. At first 

 the ova are semi-opaque, pale yellow, and apparently speckled 

 minutely, which is owing to the granular yolk ; afterwards they 

 become clouded with light-brown blotches, and three dark spots 

 make their appearance, one for each eye and one for the viscera ; 

 these spots, in the next stage, approach each other, and a faint 

 outline of the future Argonaut is visible, a club-shaped embryo, 

 rounded in front and tapering behind. The front part is then 

 lobed ; a black mark for the horny mandibles is perceived, and 



