vs LIMAX CINEREO-NIGEFR. 
The oOLFAcTORY sense in L. c/nereo-niger is remarkable for its power and 
precision. M. Colbeau relates that the fine specimen of var. malacologorum 
in his possession escaped many times from the box in which it was confined, 
through a small hole five mill. in diameter, and after wandering about 
several days in the garden, on two occasions re-entered the box by the same 
small hole, evidently attracted by the mushrooms grown therein. 
Variation.—Colour variation in the Limacidee would seem to reach its 
acme of development in this species, individuals of which display all shades 
of colour, ranging from uniform white, through grey, yellow, brown, and 
red to uniform black, with all the variations to which their combinations 
may give rise. ‘I'his marvellous variety in colour and marking leads us to sus- 
pect, as suggested by Simroth, that this rich and elaborate pigmentation is 
of high biological importance to this species in the struggle for existence. 
The complex causes which influence or inhibit the evolution and external 
disposition of colouring matter in the Limacide are still little understood; 
it has, however, been demonstrated by Simroth that the intensity and shade 
of the various colourimgs are dependent in a measure upon temperature, 
especially during the growth period. Cold, inclement seasons or districts 
favour the increase of the black pigment, and pale or entirely eradicate 
the red, while warm seasons or areas foster the development and intensi- 
fication of the red pigment, resulting in the gorgeous varieties recorded 
from Italy and other southern countries; but it must not be overlooked 
that the distribution and character of the external pigmentation is also 
largely influenced by the necessities of the animal, either by inducing a 
closer assimilation to the peculiarities of the environment, and therefore a 
more effective concealment from its enemies, or conversely by the develop- 
ment of a brighter colouring, rendering it more conspicuous, and therefore 
probably acting as a warning colour.' 
Like its close ally Limar maximus, the present species may also be 
regarded as trichroic or triple-tinted in its pigmentation, and has probably 
passed through a similar course of colour-changes, but the colour-develop- 
ment has advanced much further, a response to the more freely exposed life 
it leads and the consequent greater vicissitudes of temperature, ete., to 
which it is subjected. 
The probable sequence of its pigmentary evolution is shown by the 
primary or secondary tints sometimes extending over the Jocomotor or 
mid-area of the sole, beyond the darker tertiary colouring which has not yet 
advanced beyond the side areas and is still very superficial in its disposition ; 
further evidence of the progress of colour evolution is adduced by Simroth, 
from which we gather that in the youthful stages of the species in the 
more advanced districts there is a prevalence of the simple colouring which 
characterizes adults in those less favourable or more remote, as in L. mon- 
tanus of South Tyrol, L. engadinensis of Fast Switzerland, ete. 
L. cinereo-niger, judged by its more extended range altitudinally and 
also geographically wherever sufficient and precise observations have been 
made, by the situations it usually inhabits, by the more primitive character of 
its teeth, by the point of attachment of the penial retractor, and other pecu- 
liarities, is probably a more primitive and earlier form than Z. marimus, but 
the extreme climatic conditions under which the species lives, have enabled 
it to outstrip in its external pigmentation the Z. maaimus, which evinces 
such a partiality for the vicinity of human abodes, and is therefore more 
prone to be carried by commerce to, and become naturalized in distant lands. 
1 Monog., i., p. 327 and p. 330. 
