Chap. IX. 
MOLLUSCS. 
325 
“gons, ne saurait mettre en doute la seduction deployee 
“dans les mouvements et les allures qui preparent et 
“ accomplissent le double embrassement de ces her- 
“ maphrodites.” These animals appear also susceptible 
of some degree of permanent attachment : an accurate 
observer, Mr. Lonsdale, informs me that he placed a 
pair of land-shells {Helix pomatia), one of which was 
Aveakly, into a small and ill-provided garden. After a 
short time the strong and healthy individual disappeared, 
and was traced by its track of slime over a wall into an 
adjoining well-stocked garden. Mr. Lonsdale concluded 
that it had deserted its sickly mate ; but after an 
absence of twenty-four hours it returned, and apparently 
communicated the result of its successful exploration, 
for both then started along the same track and disap- 
peared over the wall. 
Even in the highest class of the Mollusca, namely the 
Cephalopoda or cuttle-fishes, in which the sexes are 
separate, secondary sexual characters of the kind which 
we are here considering, do not, as far as I can discover, 
occur. This is a surprising circumstance, as these 
animals possess highly-developed sense-organs and have 
considerable mental powers, as will be admitted by 
every one who has watched their artful endeavours to 
escape from an enemy . 2 Certain Cephalopoda, however, 
are characterised by one extraordinary sexual character, 
namely, that the male element collects within one of 
the arms or tentacles, which is then cast off, and, 
clinging by its sucking-discs to the female, lives for 
a time an independent life. So completely does the 
cast-off arm resemble a separate animal, that it was 
described by Cuvier as a parasitic worm under the name 
2 See, for instance, the account which I have given in my 1 Journal 
of Researches/ 1845, p. 7. 
