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THE CEPHALOPODA 323 
The terminal reservoir is known 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- “a 
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 sae. 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 nae 
splits open and allows the spermatozoa fale genital organs of Loligo, ven- 
contained in it to escape. These struc- tl aspect. I, seminal vesicle ; 1, 
i spermiduct; III, testis; IV, genital 
tures, which are comparable to the coelomic capsule; V, origin of the 
: spermiduct in the coelomic genital 
spermatophores of certain pulmonate capsule; VI, spermatophore sac; VII, 
. prostate; VILI, genital orifice. (After 
Gastropods, are generally rather smal] Sharemor yee 
but they attain a length of eight centi- 
metres in Eledone, 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 JVautilus 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 
