TYPE MOLLUSC A. 355 



Nautilus, is that of tlie left side. The oviduct opens into the 

 mantie-eavity at the extremity of a well-marked papilla, its 

 terminal portion being" richly supplied with glands, and in 

 addition in some forms two small pear-shaped glands are 

 attached to it in this region. In' connection with the female 

 ducts there should be mentioned a pair of glands which take 

 part in the formation of the investments of the ova, but which 

 open quite separate from the oviduct into the mantle-cavity. 

 These are the nidamental glands which are present in the 

 majority of forms, excluding the Octopoda, and consist of a 

 pair of large pyriform structures lying on the posterior sur- 

 face of the visceral mass ; in connection with them in some 

 forms are developed accessory nidamental glands consisting 

 of a central and two lateral portions whose ducts open into 

 the mantle-cavity in' close proximity to those of the nidamen- 

 tal glands proper. As stated, the gelatinous mass within 

 which the ova are imbedded is probably manufactured by 

 these glands. 



The testis in its general relations resembles the ovary, 

 being single and enclosed in a capsule which is a portion of the 

 viscero-pericardial cavity. The organ is attached to the wall 

 of the capsule by a thin band of tissue and is in most cases 

 almost completely surrounded by the capsule, into the cavity 

 of which the spermatozoa are shed when mature. From the 

 wall of the capsule the vas deferens arises and is usually a 

 single tube opening upon the left side of the body into the 

 mantle-cavity. In Nautilus there are, as in the female, two 

 ducts, the right, however, being functionless, but in other 

 forms a paired arrangement is very rare. The proximal por- 

 tion of the duct is a coiled vas deferens, which opens into a 

 thick-walled glandular seminal vesicle which on its part by 

 means of a narrow duct passes into a saclike structure known 

 as Needham's pouch which finally passes into the muscular 

 penis. In most forms the duct connecting the seminal vesicle 

 with Needham's pouch receives the secretion of a special gland 

 known as the prostate. 



The majority of the accessory structures connected with 

 the male ducts are concerned in the formation of cases or 

 spermatophores in which a number of spermatozoa are en- 



