146 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



Each renal <>r pericardial pore is surrounded by :i lip, a raised thickened portion of the mantle. 

 The pericardial pores are the largest of the six, being 3 millimeters in length. The renal pores are 

 each 2 millimeters in length. The lips of the latter are divided into inner and outer parts, forming 

 tight valves. The main axes of the pores are all directed obliquely backward and outward. 



ANUS. 



In the median line of the mantle, just posterior to and above the anterior renal sacs, is the 

 anus (Fig. 3, A). Its edges are plaited and project slightly from the surface of the mantle. The 

 anus is situated upon the thickened posterior portion of the mantle, about 8 millimeters from the 

 line along which the mantle joins the body wall. The anus of Valenciennes's specimen was 

 situated upon the body wall between and at the middle of the shell muscles. Valenciennes has 

 shown himself too good an observer for us to consider that he. made a mistake in this description 

 and figure. It was simply a very peculiar and rare abnormality. 



REPRODUCTIVE APERTURES. 



The reproductive apertures of both male and female Nautili are paired. The two ditfei 

 from each other in the same sex, and the right apertures are differently formed in the two sexes. 

 The apertures of the female present the simplest conditions. The aperture of the functional 

 oviduct is upon the right side of the body, at the tip of a projection from the body wall 

 (Fig. -t, O V), immediately anterior to the crease formed by the junction of the mantle with the 

 body wall and about halfway between the right shell muscle and the median line of the body. 

 The transverse slit-like aperture is borne upon a dorso-ventrally flattened plaited projection of the 

 body wall. This projection, which forms the tip of the oviduct, is, in preserved specimens, of a 

 dark-brown color. The color is the same as that of the nidamental gland, which Willey tells us 

 is a bright yellow in the fresh condition; so the tip of the oviduct may also be of a very different 

 color in the living than in the preserved specimens. It forms a projection 12 millimeters in 

 width, 5 millimeters in thickness (dorso-ventral measurement), and 10 millimeters in length. The 

 length of the dorsal side is not quite so great as that of the ventral side. The walls are thick and 

 transversely folded, and are evidently glandular. In spite of its comparatively large size the tip 

 of the oviduct is not a conspicuous part of the pallial complex, being situated so low in the crease 

 formed by the mantle and the ventral body wall. 



The aperture of the left reproductive duct is an exceedingly minute pore on the left side 

 of the bod\-, in the crease formed by the union of mantle and body wall, and located imme- 

 diately posterior to or above the base of the posterior (the smaller) gill. The position anil 

 form of this aperture are the same in both male and female Nautili. The aperture leads 

 into the organ commonly called the pyriform sac which there seems to be good reason to 

 consider as the vestige of the left reproductive duct of Nautilus. It has the same structure 

 in both sexes. 



The functional male efferent duct opens at the tip of the penis, a tubular organ lying in 

 the median line of the ventral body wall. (Fig. 3, P.) The tip of the penis only is free from 

 the body wall. The cavity of the penis is divided a little back of the tip of the organ by a 

 longitudinal partition into two portions, which are parallel for a certain distance. They then 

 fork, the left branch turning outward and backward toward the minute left reproductive 

 aperture, and soon ending blindly. The right branch continues to the right to that region of 

 the crease between the mantle and the body wall where the tip of the oviduct is located in 

 the female. It here penetrates the body wall and becomes continuous with the vas deferens. 

 Just back of the penis, which term refers to that median structure within which the efferent 

 ducts are parallel to each other and finally unite, and are contained within a common wall, 

 the right duct is swollen to form a considerable sac, the spermatophore sac. This forms a 

 protrusion of the body wall which is quite noticeable. The structure of these parts will be 

 described in more detail in the section treating of the reproductive organs. 



