324 THE CEPHALOPODA 
common sheath and provided with a circular glandular area: the 
eight remaining tentacles of the lobe are unaltered. The modifica- 
tion usually affects the left side (Fig. 255, p), but it has also been 
observed on the right. On the side opposite to the spadix the four 
corresponding tentacles are isolated from the other eight and 
constitute the so-called antispadix. In the Dibranchia the 
hectocotylised arm of the Decapoda generally belongs to the last 
pair, counting from the anterior or dorsal face, that is to say, the 
fourth pair of true arms, but to the third pair in the Octopoda. 
In the majority of the Oigopsida it is 
the left fourth arm that is hectocotylised 
(Onychoteuthidae, Ommatostrephidae), as 
is the case in Loligo and Sepia; in Rossia 
and Semola the fourth left arm is hecto- 
cotylised and the fourth right partially 
so; in Jdiosepion and Spirula both arms 
of the fourth pair are hectocotylised, and 
in the last named they are contained in 
a common envelope. In the Octopoda 
the third left arm of Scaeurgus, the third 
right arm of Octopus and Eledone, and 
the second of the right side of Cirrhoteuthis 
are hectocotylised. In noploteuthis, 
Eledone, and Octopus the extremity of 
the hectocotylised arm is modified and 
assumes the shape of a spoon; in Sepia 
the base of the arm is affected, the 
modification consisting in the disappear- 
ance of the suckers; in IJdiosepion and 
fossia and Loliolus the suckers disappear 
over nearly the whole length of the arm, 
and in the two first named a longitudinal 
membrane is developed along its exterior 
aspect and abundant mucous glands along 
its internal surface. In some Octopoda 
inal of Gey eatemutete sow the eetocotylised arm is still more pro- 
view. h, the third arm of the right foundly modified, inasmuch as it is auto- 
side, or hectocotylus; i, funnel; a ra > 5 
11, ¢2, #3, t4, the tirst, second, third, tomous. This peculiarity is found in 
of ie hectoontzice 9 ate mien the Philonexidae and Argonautidae. In 
ae He ONSTE pte Geen Ocythoé and Tremoctopus the third right 
Lankester, after Gegenbaur.) arm is modified (Fig. 287, h), in Argonauta 
the third left; but in all these genera 
the modified arm constitutes a veritable hectocotylus, that is 
to say, a caducous organ. This hectocotylus originates, and 
apparently also is regenerated, in a capsule or cyst in which it 
lies coiled up on itself: being shielded from the light, it is 
Fic. 287. 
