6 ZOOLOGY OF THE VOYAGE OF H.M.S. SAMABANG. 



vestige of any muscular attachment. In the specimen of A. gondola from which the accompanying drawing 

 was made, 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 sufficiently matured to enable me to trace, under 

 the microscope, the early indications of the being of the Argonaut ; and although the progress is not 

 followed very far, it is 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 difference of any importance 

 appears to be that Poli regarded as 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 the eyes are large and prominent; 

 the yolk-bag, or vitellus, is next seen very distinctly, and the processes extending from the head are more 

 elongated. Here, however, I was obliged to stop, this being the most perfectly developed embryo I could 

 find amongst the ova. The eggs in contact with the front part of the body- whorl of the shell, where the 

 egg-mass is attached by the glutinous threads, are the most forward in their development, while those in 

 the posterior part of the chamber are much less matured. 1 A.A. 



3. SPIRULA, Lamarck. 

 Description of two mutilated specimens of Spirula Peronii, with some observations on S. australis and reticulata. 



Plate IV. 

 (By Peofessor Owen, F.R.S.) 



It is remarkable of the two known genera of polythalarnous Cephalopods, Spirula and 

 Nautilus, that both should be noted for the extreme rarity of the entire animal, as compared 

 with the frequency of the shell in collections of Natural History ; and this is more particularly 

 the case with the Spirula, on account of the mutilated state, with a single exception, of all 

 the few examples of the animal or soft parts hitherto described. The specimen captured by 

 Capt. Sir Edward Belcher in the Indian Archipelago, is no exception to the rule. Like that 

 inspected and described by Professor De Blainville in the Annates Francaises et Etrangeres 

 d' Anatomie et de Physiologic, pour V Annee, 1837, vol. i. pp. 369, 382, the head has been 

 torn from the body, and the opposite extremity, or the part answering to that which supports 

 the appendages, described as fins in M. de Blainville's memoir, is also wanting ; so that the 

 last whorl of the shell is terminal, as in the specimen figured in the Atlas of the Voyage of 

 Peron and Lesueur, pi. 30. fig. 4. It does not necessarily follow, however, that this difference 

 is the result of mutilation, and that the terminal part in question has existed in these speci- 

 mens and been torn away. At least in Sir Edward Belcher's specimen, the rounded posterior 

 terminations of the lateral lobes of the mantle, fig. 1, 4, 5, 7, d d, are entire, and covered by 

 the epiderm, which shows no sign of laceration or abrasion. 



To Lamarck l and Peron 2 we owe the knowledge of the acetabuliferous character of the 

 Spirula ; whence, after the dissection of the Nautilus, its dibranchiate organization was to be 



1 Encyclopedie Methodique, Atlas, Coquilles, pi. 465, fig. 5, a b. 2 Loc. cit. 



