174 M. Vrolik on the Anatomy of the Pearly Nautilus. 



wliieli I have had the opportunity of dissecting some time ago 

 at Harlem^ with my colleagues Van Breda and Reinwardt. Al- 

 though the dissection is not completely finished, and I resei-ve 

 for a more extended memoir the filling up of the hiatuses which 

 I am now obliged to leave, I have thought it convenient to give a 

 brief resume of the principal facts which we have observed, as it 

 may tend to determine the difierences of opinion which seem to 

 exist on the subject ; and I take advantage of my visit to England 

 to communicate to you the extract of om* observations, which 

 M. Van Breda has been so good as to send me for that purpose 

 from Harlem on the 24th of July. 



I must fii-st inform you that the Academy of Sciences at Har- 

 lem has received two complete specimens of the Pearly Nautilus ; 

 the Society owes one to the kindness of M. Serriere, Governor • 

 of the Mollucca Islands, who, learning from the iVnnual Report 

 of the Harlem Society then- desire to possess a complete example 

 of that interesting animal, generously transmitted one that had 

 been caught by a hook in the bay of AmbojTia. It has been de- 

 posited in the museum of the Society. 



The second specimen was bought by Colonel Boelen of a fisher- 

 man, who had also taken it at a depth of many fathoms in the 

 same bay. This Nautilus lived two days on board the Boreas, 

 of which M. Boelen is the commander. It was preserved mth 

 great care in spirits of \\me, and after having been drawn by 

 M. Verhuell it was submitted to my scalpel. The principal re- 

 sults of its dissection are, — 



1. That the chambers of the shell contain only gas. We 

 opened several under water ; the gas which we collected con- 

 tained a greater proportion of azote than the atmospheric au* 

 does. ]\I. Van Breda, who analysed it, did not detect the slight- 

 est trace of carbonic acid. 



2. That the animal is attached to the shell only by the siphon. 

 The two muscles, by which it shovdd adhere to the shell, accord- 

 ing to the opinion of many naturalists, are applied only to the 

 horny membrane or girdle, which Owen has so well described in 

 his remarkable work*. This membrane does not itself adhere to 

 the shell, so that there is no difficulty in detaching the horny 

 membrane in question without the slightest laceration, both from 

 the surface of the muscles and from that of the shell between 

 which it is situated. 



3. That the structure and position of the internal organs are, 

 in general, such as Owen has described in his admirable memoir. 



4. That the two mandibles are horny, but covered by a bluish 

 calcareous matter, which had evidently been lost in the speci- 



* Memoir on the Pearly Nautilus, 4to, 1832, p. 9. 



