100 
VARIATION IN BANDING. 
Fio. 200 . — Helix ncufornlis L. x l.V, 
Church Kenton, Voiks., 
Collected by Mr. W. I). Roebuck, 
Showin.s; the tendency of the 
bnnding to become conlluent at the 
aperture of the shell. 
susceptibility to climatic or meteorological influences has been 
termed Ilormomorpliism. 
The characterof the baudingsometimes 
changes very markedly during growth in 
.some individuals. In the early whorls 
the bands may be quite separate and 
distinct, and afterwards become gradually 
united together as the termination of 
growth or maturity is approached; tliis 
change arising from the cxce,ssive 
development or hypertrophy of the colour glands of the mantle. 
This transverse coalition of all the bands may also take place 
towards the completion of each little stage of growth, each recom- 
nicnceinent exhibiting a practical atrophy of the colour glands or at 
least a temporary failure of their func- 
tion, and also a. rapid resumption of 
t V \ ^ , Xwlfc excessive secretive power, 'i'his rhythm- 
ical alternation of the hypertrophy and 
practical atrophy of tlie colour glands 
of the mantle margin results in the form 
of IlrU.r iK'mwviIls which has heen called 
the variety iiudiildtn by Gentiluomo. 
'I'lie more or le.ss comi)lcte permanent atrophy of the glands forming 
the banding may, however, occasionally 
take place at the termination of one of the 
jjerioils of growth, before the maturity of the 
"hell, the growth afterwards made being 
wholly or ])artially deficient of the banding, 
ilistinctly present on the lu’eceding whorls. 
In other cases, on the contrary, the 
secretory power of the glands may be 
undevelopo<l or dormant duilng 
growth, and gTadually, or more rarely 
suddenly develop in full strength as 
maturity and the period of fullest 
vigour is approached. 
'i'he llammular or flame-like markings arc tho.se which are some- 
what irregularly shaped and may be considered to fre([uently 
originate from a disintegration of the jn-imitive spiral or longitudinal 
2()7 . — Helix fietfioralis var. 
unditlaia lleiuiluonio X 1\, 
I’lagctlon, near Bristol, 
Collected i)y Miss K. M. Hele, 
Sliowint; the alternation in the 
secretive power of the colour glands 
funning the banding. 
Kig. 20<S. — H . hortensis Mull., 
Krutigen, Switzerland, 
Showing the abrupt cessation 
of the normal banding. 
A 
Kk 
2(H). — Helix pisana'^\'\\\\. x 1',. 
Tenby, South Wales, 
Collected by Mr. J. R. II. Masefielil, M.A., 
Showing the abrupt commencemetu of 
distinct banding. 
