66 Prof. J. Van der Hoeven on the Anatomy 



spond then with a greater fineness to those laminse, which, with 

 Owen, in his description of the female Nautilus, bear the name 

 of olfactory organ. The fine membranous parts, on the other 

 hand, which are present in the female at the commissure of the 

 external labial slips, are entirely wanting in the male, and are 

 represented by the retiform tissue that covers on the inside the 

 commissure of the outermost tentaculiferous slips. 



Let us now revert to the spadix on the left side of the male 

 Nautilus. This body is 6 or 7 centimeters long, 4^ or 5 centi- 

 meters high, and at the base 3 centimeters broad. A transverse 

 section (Pl.V. fig. 1) plainly shows that it consists of four tentacula, 

 of which three in particular are distinguished by their remark- 

 able circumference, and of which the sheaths have mutually 

 coalesced*. The undermost tentacle has only a short mem- 

 branous sheath at its base, and elsewhere lies free along the 

 inferior margin at the outside of the chief body of the spadix 

 formed by the three remaining tentacles. On the outside of the 

 membranous sheath of the uppermost tentacle of the spadix lies, 

 close to the anterior extremity, a flat disk of an elongated round 

 form, of 2^ centimeters in the smaller diameter and 3 centi- 

 meters long. This disk is perforated by many small round 

 apertures which are surrounded by a slightly raised border; 

 they are distant from each other about 1 mm., in some places 

 nearer together. A longitudinal section of the thickness of the 

 disk shows that it consists of many follicles, which are perpendi- 

 cular to its surface, are distinguished by sacciform dilatations of 

 the walls, and have their openings at the apertures just mentioned. 



To revert to the second principal portion of the body (p. 61), 

 we may add, that the two swellings which are present in the 

 undermost part of this portion in the female, are absent in the 

 malef. The glandular organ, composed of many laminae, which is 

 here attached to the inside of the mantle in the female Nautilus, is 

 wanting in the male ; consequently Owen's opinion is confirmed, 

 which regards this organ as connected with the sexual apparatus, 

 and ascribes to it the secretion of a covering for the eggs J. 

 Moreover, it seemed to me that the mantle in the male Nautilus 

 is shorter and leaves the eyes almost uncovered, whilst in female 



* These tentacles present to the naked eye a structure corresponding to 

 that which in the ordinary tentacles is observed by means of the microscope. 

 Comp. R. Owen, On the structure and homology of the cephalic tentacles 

 in the Pearly Nautilus, Annals and Mag. of Nat. Hist. xi. 1843, p. 308. 



t Owen, Memoir, p. 9. pi. 1 e, pi. 2 e ; compare my figures, Transact, of 

 the Zool. Soc. iv. 1. pi. 5 h, pi. 6. fig. 3h h. 



X " A glandular apparatus which, if not peculiar to, is in all 



probability more strongly developed in the female than in the male Nautilus 

 Pompilius," p. 'J. See further the description of this part, ibid. p. 43. 



