THE CEPHALOPODA 



323 



The terminal reservoir is knoAvn as Needham's sac or the spermato- 

 phore sac (Fig. 286, VII). Between the vesicula seminalis and the 

 prostate the spermiduct may exhibit a small tubule which opens 

 into the coelom (Sepia), and in exceptional -cases (Philonexis) the 

 deeper part of the spermiduct may be divided into two canals, 

 both of which open into the portion of the coelom containing the 

 testis. 



The sperm lies free in the initial part of the spermiduct, but 

 when it reaches the first glandular pouch it begins to be surrounded 

 by a tube-shaped envelope or spermato- 

 phore. In the Dibranchia these tubes 

 are completed in the interior of the 

 prostate, and are then arranged parallel 

 to one another in the reservoir or 

 spermatophore sac. When mature they 

 are passed directly from the genital 

 duct into the funnel, the terminal 

 papilla of the spermiduct being ex- 

 tended for this purpose, and thus they 

 enter the hectocotylised arm. Each 

 spermatophore consists of an elastic 

 tube invaginated into itself ; the deeper 

 part of the invagination constitutes the 

 spermatic reservoir, and the more ex- 

 ternal part, forming the connective, is 

 greatly contracted and often coiled into 

 a spiral. When the ripe spermato- 

 phore is expelled the connective is 

 extended and evaginated, carrying in 

 its interior the reservoir which causes 

 it to burst: the reservoir in its turn 

 splits open and allows the spermatozoa 

 contained in it to escape. These struc- 

 tures, which are comparable to the 



Fio. 286. 



Male genital organs of Loligo, ven- 

 tral aspect. I, seminal vesicle ; 11, 

 spermiduct; III, testis; IV, genital 

 coelomic capsule ; V, origin of the 

 . spermiduct in the coelomic genital 



Of Certain pulmonate capsule ;VI, spermatophore sac ; VII, 

 /7 11 !! prostate ; VIII, genital orih'ce. (After 



Gastropods, are generally rather small ; f, uve nioy.) 

 but they attain a length of eight centi- 

 metres in Ekdone, and in the Octopoda with an autotomous hecto- 

 cotylus, they are as much as fifty centimetres long when unrolled. 

 In Nautilus their structure is simpler : they have the form of coiled 

 tubes and are little more than thirty centimetres long. 



The organ of copulation in Nautilus is the spadix, in the 

 Dibranchia the hectocotylised arm. The spadix of Nautilus is a 

 modified region comparable with the hectocotylus of the interior 

 ventral lateral lobe. The modification is persistent and involves 

 four tentacles, which are united to form a projection contained in a 



