316 
GLANDULAR yY.STEiM — MUCOUS FILAMENTS. 
witliiii which is accuiuiikted tlie viscid mucus secreted tlie folli- 
cular tissue l)y which it is densely invested. The gland opens upon 
the lower snrhice of the foot towards its anterior end and corresi)onds 
to or is probably homologous with 
the byssal gland of the Pelecypoda, 
secreting a viscid and very tena- 
cious mucus by means of which 
tirm adhesion can be secured to 
their resting jilace, or a strong 
tdament can be formed for siuspen- 
sion or descent from an elevated 
position. 
I’he l\Iucous Filaments formed 
by the attenuation of the viscid and 
tenacious .slime emitted from the 
foot glands, which, by its property 
of hardening when in contact with 
air or water, supplies the mollusca 
with a ready means of locomotion or 
(> 07 . — Mucous ir.'ick on smTacc of suspeusion fioiu Suitable clevatcd 
added greatl}' to our knowledge of this subject. 
The Ib'itish Isles, owing to their cool and dami) climate, are 
es[)ecially favourable countries for the oliservation of this curious and 
interesting habit amongst our land mollu.sca, the .slugs pos.se.s.sing this 
]'(jwer in tlie most marked degree, L'nmi.r inarfjinatm IMull. olim 
JJnui.r (trlxinnii Bouch.-(’h. jierforming these actions with e.special 
ease and celerity, though other .sjiecies under similar circumstances 
form the.'<e su.spensory filaments with great facility, lowering them- 
selves from a liranch or other elevated object to a lower level 
hy attaching the viscid mucus accumulated at the tail to the branch 
or other object upon which the animal may happen to be and then 
by launching into the air, attenuating and lengthening out into a 
slender thread-like filament the accumulated mucus, a fresh supply 
for its increasing length being afforded by its continued free exuda- 
tion from the foot-gland.s, which is carried towards the tail by the 
active undulatory motion of the sole or locomotory disc, the sides 
of the foot being brought nearer together and forming a guide or 
