﻿16 BRITISH FOSSIL CEPHALOPODA. 



It is of a flattened oval form, with the long axis longitudinal. At the time of its ex- 

 amination by Yan der Hoeven there were spermatophores in the course of development 

 and extrusion ; and at that time it was the second largest viscus in the body, but it 

 did not encroach particularly on the hinder part of the visceral cavity. It is enclosed 

 in a fold of membrane, and consists of nine or ten more or less conspicuous lobes, 

 made of a number of acini of a brownish-yellow colour, with their distal ends blind 

 and their proximal ends attached to the branches of the efferent vessel into which 

 they open. This efferent vessel passes forwards to near the right-hand corner of 

 the testis, where it has a prominent papillary aperture. Immediately opposite to 

 this is a groove in another smaller gland lying in front, and to the right into which 

 the prominence loosely fits. At the base of this groove is a slit which leads into 

 a larger cavity, from which passes a fine duct leading into a wider tube, which makes 

 a few convolutions in the smaller gland and ends in sac at the anterior left-hand side. 

 In this course the gland, which consists of many lobules of blind tubules, supplies an 

 additional secretion. From the last-mentioned sac, which is contained within the 

 gland, passes a thick-walled tube into the spermatophore sac, or " Needham's pouch," 

 lying to the right of the median line of the body. This is a cylindrical bladder with 

 very firm walls and longitudinal folds within. It has an oblique longitudinal 

 partition, which opens in front and gives exit into the base of the penis. This 

 latter organ is obtusely conical and lies in the mid line about halfway along the 

 course of the shell-muscles. It is concrescent with the body on the inner side, and 

 has a transverse slit at its extremity with swollen margins. In the spermatophore 

 sacs are seen numerous convoluted spermatophores, which do not attain perfection 

 till reaching this cavity. They have no covering here ; but some are always found 

 between the smaller tentacles of the labial processes, in which position they are each 

 encased in a structureless cover, which they could not have had when passing 

 through the narrow penial canal. There is no nidamental gland in the male, but 

 these enclosed spermatophores are found in close proximity to the glandular part of 

 the spadix from which they may well have received their covering. In this case 

 the process which forms this spadix may be looked upon as a hectocotylised arm. 

 Each spermatophore is a convoluted tube, about ten or twelve inches long and 

 half a line in diameter, with a twisted and retroverted end, and contains within it 

 a spiral thread (as in the trachea of an insect), to which the spermatozoa are attached 

 by their thin extremities. 



Such are the known features of the organisation of the Nautilus. Unfortunately 

 at the present day we are in total ignorance as to its development. 



It would occupy too much space and not be to our immediate purpose to enter 

 into similar details with respect to the organisation of the Dibranchiates, which will 

 come more appropriately as introductions to those parts which treat specially of 

 their British fossil representatives. When the two orders are compared, it will be 



