FOOD ; MIGRATION ; PROPAGATION. 809 



In his account of the specimen of Spirula obtained by Sir Edward Belcher during 

 the voyage of H.M.S. Samarang 1843 — 1846, Owen (Zoology of the " Saniarang," London, 

 1850, Mollusca, p. 6) called attention to the fact that the two known genera of ex- 

 isting polythalaraous Cephalopods were noted for the extreme rarity of the entii-e animal 

 as compared with the frequency of the shells in collections of Natural History. In the 

 remaining Report on the Mollusca of the " Samarang," Messrs Arthur Adams and Lovell 

 Reeve recorded the fact that no living Nautilus was seen during the whole course of the 

 expedition, although it was assiduously sought for. 



There is not much to be added here concerning the propagation of Nautilus. Some 

 animals breed freely in confinement, others become egg-bound, and others again lay sterile 

 eggs, as Nautilus did in my cages. I obtained some evidence that the captivity had the 

 effect of interfering with the normal intercourse of the sexes. On one occasion in parti- 

 cular I had been keeping a male (in which owing to an injury to the hood the sperma- 

 tophore in the buccal recess protruded at the surface as in PI. LXXVII. fig. 5) under 

 careful observation for several days. Eventually the spermatophore was discharged from 

 its cyst, and I found it lying on the floor of the cage. 



This is what inclines me to believe that it is necessary to work with a large 

 installation, a specially fitted-up aquarium of large size with concrete walls, in order to 

 rear the embryos of Nautilus successfully. I have no doubt that the shell and several 

 chambers are formed while the embryo is still in the egg-capsule, and that the young 

 Nautilus hatches out with the general facies of the adult. 



I tried artificial fertilisation without success, and I do not think it is practicable. 

 The very young shell which is in all probability formed within the egg-capsule has been 

 called the nepionic shell, and may be easily recognised by its colour and finer grain in 

 young shells, being separated from the subsequent shell-substance by a well-marked suture, 

 which is visible in the umbilicus of the shells of N. macroinphalus and N. utnhilicatus. 



The clear brown vitellus of the egg is surrounded by viscid colourless albumen 

 which accumulates at the poles. Between the yolk and the albumen there is a delicate 

 hyaline vitelline membrane. The vitellus is larger than that of any other known Cephalopod 



When the females reach maturity, the bilabiate vagina and the nidamental gland 

 become enlarged, protuberant, and turgid, and the edge of the shell is thickened. The 

 nidamental gland frequently assumes a greenish colour. Thus a female N. jjompilius 

 with submature ovarian ova had a moderately developed, yellow-coloured nidamental gland 

 which had not become turgid. In another of the same age the yellow gland was tinged 

 with a greenish colour. In another the sub-turgid nidamental gland was of a dull 

 greenish or yellowish-gi'een colour. In a nearly mature female the nidamental gland 

 had a pronounced green colour. Apparently the gland does not always turn green, as 

 I have recorded instances of nearly mature females in which it exhibited a rich cream- 

 yellow coloration, the largest ovarian ova, in such specimens, attaining a length of 

 17"6 mm. and a maximum breadth of 15 mm. 



The organ of Valenciennes also becomes turgid and functionally active with 

 abundant secretion of mucus at maturity. 



The eggs of N. pompilius differ very slightly from those of N. macromphalus^ , and 



• Willey, A., "The oviposition of Nautilus inacromphalus." P. R. Soc. London, 1897, Vol. 60, pp. 467—471, 6 figg. 



