1708 
ON SIMPLE STRIATED MUSCULAR FIBRES, 
The principal molluscan muscles which I have examined are the 
following: — retractor muscles of eye of Helix aspersa, muscles of the 
odontophores and buccal mass of the same species, the same muscles 
in a species of Limax, a species of Aplysia^ a species of Triton 
and a species of Patella ( P. tramoserica J , the adductor muscles of 
Petricola and of Lima. The only one of these that exhibits 
anything that can be called regular and well-marked transverse 
striations is the last, in which the fibres closely resemble those of 
Pecten as described and figured by Blanchard. In the other cases 
mentioned, when an appearance of transverse striation presents 
itself (as in some of the fibres of the buccal mass of Helix and 
Aplysia), this is due to the arrangement of the granular matter of 
the core, and not to striation of the cortical muscle-substance. 
With Lima, however, as with Pecten, and probably in other 
instances which I have not examined, the case is quite different. 
Here the transverse markings are very distinct and very regular. 
Blanchard regards them as due to the same cause as in the 
Arthropoda and Vertebrata — the substance of the fibre being 
made up of alternating zones of two kinds of material, differing 
from one another in optical properties and in behaviour to staining 
agents ; and he also describes narrow discs of doubly-refracting 
material crossing the simply-refracting zones and representing 
Krause’s membranes. Fol, on the other hand, maintains that the 
appearance of striation in this as in other instances in which it has 
been described as occurring among the Mollusca, is due to the 
spiral twining of the fibrillar cortical layer round the granular 
axis. 
When the fibres in question are treated with Heidenhain’s 
hsematoxylin a series of transverse or oblique bands come more 
distinctly into view owing to the action of the staining agent. 
These bands which become stained, are separated from one another 
by narrower uncoloured bands, and, according to Blanchard’s 
account, the broad bands are doubly refracting, the narrow bands 
singly. According to Fol, the broad bands are the spirally-coHed 
fibrillar substance of the cortex, the light spaces between them 
