DEVELOPMENT OF THE ARGONAUT. 525 



calcareous nest, which she firmly 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 attach- 

 ment. In the specimen from which I made the drawings 

 which will be given in the "Zoology of the Samarang," 

 the ovary was distended with ova, but in a much less ad- 

 vanced stage of development than those deposited in the 

 shelly nidus. Some of these latter were sufficiently 

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

 early indications of the being of the Argonaut, and al- 

 though I have not followed the process very far, it is 

 sufficient to ascertain the similarity, in a great measure, 

 with the changes observed by Poli in the same genus, with 

 whose remarks I have compared my own : the only differ- 

 ence, of any importance, appears to be, that Poli has 

 regarded as the shell what I have called the yolk-bag. 

 At first, the ova are semi-opaque, pale-yellow, and appa- 

 rently minutely speckled, which is owing to the granular 

 yolk seen through the delicate shell of the egg; 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, ap- 

 proach each other, and a faint outline of the future 

 Argonaut is perceived in the form of a club-shaped 

 embryo, rounded in front and tapering behind; the front 

 part then becomes lobed, a black mark for the horny 

 mandibles is perceived, and the eyes become large and 

 prominent. The yolk-bag or vitellus, is next seen very 



