198 _ ARION SUBFUSCUS. 
the body a nearly black; this greater uniformity is naturally to be ex- 
pected, as A. subfuscus 18 a more ‘ancient species and not a dominant form. 
The junction of its distribution with the limits of the more restricted 
area inhabited by A. aéer, is complicated in those districts by the external 
approximation im aspect of the two species, a resemblance which has been 
the cause of great confusion, as many authors have, at various times, 
recorded the present species under one or other of the different names of 
its larger congener. 
On the Finnish shores of the Gulf of Finland, the var. /ennica assimilates 
in a very remarkable way to Arion ater, under which name it has frequently 
been recorded ; while the Arion lusitunicus, A. nobrei, and A. dasilvae, 
which have been described from the Spanish peninsula, are undoubtedly 
intermediate forms linking swbfuscus with ater, resembling sub/uscus in their 
internal structure but often approximating externally more closely to ater 
especially in size and colouring. 
The Arion jlagellus of Collinge, which is a 
here regarded as a simple variety of A. sub- La 
fuscus, 18 said to possess as its characteristic A ae 
feature a distinct flagellum upon the free 
oviduct, a most improbable situation for such 
an organ; but, as the illustrative figures of 
the author are somewhat carelessly or inaccu- 
rately executed, it 1s quite possible that the 
proposed species has been presented under a 
inisapprehension of the precise structure of 
ue i 
7710) OV. SP 
the animal. me 
‘The yellow colourmg of the body, though ONS Ff Kava. 
in general due to the mucous investment, is . py, 
not ‘invariably so, as In some cases the colour- Ne. re s 
ing is really due to the breaking through the Las 
skin of the superficially placed colour elands. 
The yellow dermal mucus, though so char- 
acteristic a feature, 1s also not an invariable 
Fic. 219.— Reproductive Organs 
of Arion flagellus Collinge (after 
Collinge). The ovispermatoduct is 
incorrectly represented, and some of 
the organs identified in 
trait of this species, as the darker and also 
the more pallid varieties more frequently 
emit an almost colourless slime. 
Arion subfuscus, like Limaxe arborum and 
Arion ater, offers, according to Simroth, the 
same striking evidence of the darkening in- 
fluence of altitude, as the individuals inhab- 
iting the lofty mountain ranges are invariably 
darker than those living on the plains below. 
wrongly 
Collinge’ s original figure. The figure 
is, however, here given as in the 
original, but the nomenclature of the 
organs is corrected. 
a.g. albumen gland; a. atrium ; 
ep. epiphallus ;_/7. flagellum ; 4.d. her- 
maphrodite duct ; 07. ovotestis ; ov. 
oviduct ; ow’. free oviduct ; 7, re- 
tractor muscle; s.@. sperm duct or 
prostate ; sf. spermatheca; 7v.d. vas 
deferens. 
On the contrary, ie Scharff expresses the opinion that in Ireland the 
more or less unicolorous pale yellow variety is more especially characteristic 
of the higher parts of the country while the darker typical form inhabits 
the plains. 
VARIATIONS IN COLOUR 
Var. rufo-fusea Draparnaud, Hist. Moll., 
Arion cinctus var. rufescens Dum. & Mort., 
AND 
1805, p. 125. 
Moll. Savoie, 1857, p. 7. 
MARKINGS OF ANIMAL. 
Arion rubiginosus Baudon in Drouet, Moll. Céte d'Or, 1868, p. 26. 
Arion gaudefroy? Mabille, Hist. Moll. Paris, 1870, p. 12. 
ANIMAL of a rufous tint, most pronounced on the mantle and the sides of the 
body, dorsum darker, the lateral band black or blackish. 
This form is the one selected by Draparnaud as the type of the species; but the 
rufous colouring is in many cases entirely due to the mucous investment. 
