MOLLUSCA. $21 
in the gill-sac. Whether an introduction of this organ into the 
funnel of the female takes place, is not sufficiently cleared up. 
[In certain genera of Cephalopods there is a very remarkable ac- 
cessory organ of propagation in the males, which we now proceed to 
notice. Amongst the doubtful genera of Entozoa (p. 188) Hectoco- 
tylus is recorded. It was first noticed by DetLe Cutase in Argo- 
nauta', and by him referred to the genus T'richocephalus by the 
name of J'richocephalus acetabularis. Afterwards what was sup- 
posed to be another species of the same genus was detected in Octo- 
pus granulosus Lam. by LaurILuaArD, and described by Cuvier’. 
This presented more than 100 suckers, whereas that of Dr.iE 
CuiAJE had only 35, whence it was named by Cuvier LHectocotyle 
from exatov. Kornuiker’, from his examinations of the Hectocotylus 
of Argonauta, and of another discovered by V&ERANY in Z'remoctopus 
violaceus, declared it to be the male individual of these animals 
respectively, and not a parasite. This opinion was afterwards 
shewn to be unfounded, for Vérany* found in several specimens of 
a Cephalopod, called by him Octopus Carena (male Oct. granulosus 
Lam.), that the 3rd arm on the right side was longer and thicker 
than the rest, and had a bladder at its extremity, whilst Pururprt, 
in a specimen examined by him, saw the same arm fall off on being 
touched, and found it to resemble exactly the /ectocotylus described 
by CuvIER. 
At an early period the /7ectocotylus arm is developed in its future 
position in a pediculated vesicle in which it is rolled up. The 
vesicle alone contains chromatophores’. As the development pro- 
ceeds, the containing vesicle or bladder shews a fissure on that side 
which is towards the mouth of the Cephalopod from which the hec- 
tocotylus emerges ; but since the latter is attached throughout a con- 
siderable portion of its length to the inner surface of the other side of 
the bladder, this last is turned inside out when the hectocotylus has 
escaped, and continues to be attached to it on its dorsal surface. The 
structure of the hectocotylus is the same as that already described of 
the other arms, except that in the central canal is an elongated mus- 
cular pouch, closed at the near end and terminating in a fine tube, 
and that there is a filament at the end of the hectocotylus (which has 
1 Memorie, 11. p. 225, Pl. xvi. fig. 1. 
2 Ann. des Sc. nat. XVIII. 1829, pp. 147—156. 
3 Ann. of Natural History, 1845. 
4 Mollusques mediterranéens, rere Partie. Génes, 1847—1854, s. 34 and 126, Pl. 41. 
5 See p. 824. 
