1 74 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



In a less than half-grown male, the testis formed an elongate organ situated in the genital 

 ligament immediately back of the heart. It measured 13 millimeters in length by 3 millimeters 

 in breadth. 



In this specimen the two halves of the penis were exactly alike; the right half could not be 

 traced into any communication with the vas deferens. It seemed to end blindly in the body wall. 

 I was not able to find any external opening of the vas deferens. The spermatophore sac existed 

 as a small tubular diverticulum of the right half of the penis, just as I have found it in the left 

 half of the penis of the adult. 



Upon the left side of the lower end of the testis, within the pallio-visceral ligament, is a 

 curious sac-like organ (pyr. s.). The blind enlarged end of the sac is close to the left side of 

 tin- heart. Its position varies somewhat in different individuals, being in some close — even 

 dorsal — to the heart, in others quite to the left of the heart, depending upon the shape and 

 extent of the left anterior viscero-pericardial aperture. The neck of the sac is elongated, form- 

 ing a narrow tube which opens into the mantle cavity through the pore already noticed upon the 

 left side of the body at the line of junction of the mantle fold with the body wall (pyr. ap.). 

 The sac is much flattened, causing a scarcely noticeable thickening of the pallio-visceral ligament. 

 Its walls are thin and soft and are folded upon the inner side. 



REPRODUCTIVE ORGANS OF THE FEMALE. (FIG. 39.) 



The ovary (Ov.) occupies the same position as the testis, but is somewhat smaller than the 

 fully developed testis and more rounded, forming a body 35 millimeters in length and 25 milli- 

 meters in breadth. It is suspended by ligaments in the same manner as the testis, the course of 

 the ligament of the stomach, however, being slightly different. The fold of which the gastric 

 ligament is a continuation extends from the upper end to the left side of the testis; it extends to 

 the lower end of the ovary and the gastric ligament arises from its middle (gas. 1.). 



The aperture of the ovary is upon a small protuberance of the wall upon the right side of the 

 lower end of the ovary (Ov. ap.). Anatomically the ovary opens into the coelom: actually the 

 aperture of the ovary is closely applied to the inner opening of the genital duct, so that the duct 

 is functionally continuous from the ovary. 



The posterior portion of the inside of the ovary is entirely covered by egg-follicles in various 

 stages of development. The mature follicles are about 15 millimeters in length by 1<» to 12 milli- 

 meters in diameter, each containing a single yolk-laden ovum. The older follicles are suspended 

 from the wall of the ovary by slender, membranous stalks, which are usually simple, but, accord- 

 ing to Kerr, occasionally branch. The epithelium of the inner surface of the follicle, which is 

 applied to the. ovum, is continuous over the outside of the follicle with the ccelomic epithelium 

 lining the ovary. The older follicles at least possess a three-lipped aperture at the end opposite 

 the stalk, through which the ovum escapes. Follicles from which the ova have been shed are 

 ruptured half way to their bases. Kerr finds that between the bases of the follicles the lining 

 epithelium of the ovary "thickens up into syncytial masses of protoplasm containing large round 

 nuclei, each with a large deeply staining nucleolus, around which the protoplasm tends to segre- 

 gate off more or less distinctly. The primitive ovum develops within such a heap, the nucleus 

 increasing in size and assuming more and more the character of a "germinal vesicle,' and the 

 protoplasm first becoming more distinctly aggregated round the nucleus and marked off from the 

 surrounding protoplasm and then increasing rapidly in size. As the ovum increases in size, the 

 substance of the ovarian wall grows up round it to form the follicle, while the syncytium accom- 

 panying the ovum apparently gives rise to the lining cells of the follicle." In the young follicle 

 the surface next the ovum is smooth, but as the ovum and follicle increase in size the inner sur- 

 face of the latter becomes raised into anastomosing ridges, which penetrate deeply into the ovum. 

 Willey found that the meshes formed by the ridges are much wider in submature than in the 

 less mature ova, and would presumably be found to flatten out in completely ripe ova. 



At the end of the ovum next the opening of the follicle is an area of protoplasm free from 



