326 JOHN BERRY HAYCRAFT, 
cast of the surface. One would hardly believe in sarcous 
elements here. Last summer (1880) my friend Mr. Priestley 
communicated to me a similar and independent observation of 
his own, as a contribution towards the maintenance of my views 
upon the formation of the stripes. 
The position that we have reached is this:—A muscular fibre 
presents such cross markings, varying with shifting the lens up 
or down, as a filament of homogeneous structure and similar 
shape. I have shown this experimentally, and have illustrated 
with simple experiments, which it is in the power of any one to 
test. This being the case, I have searched to find if there be 
reason to assert any want of uniformity along the fibre, using 
various methods of staining. ‘This I have failed to do, and have 
shown that the views commonly held are to be explained simply 
by the shapes of the fibres. As to the action of muscle on 
polarised light, I saw reason to dissent from the views of 
Briicke, and subsequently found my own in accordance with 
those of other recent observers. I differ from them in the ex- 
planation I offer of the two dark bands seen with crossed Nicols, 
for here, again, the shape of the fibre explains their presence 
without looking for any special structure. 
So far we are led to consider the fibre as made up of many 
ampullated fibrils, packed side by side, forming an ampullated 
fibre, these fibrils being uniform throughout, and joined together 
by some cementing material, the nature of which we will not 
hazard. The only point which would suggest a definite structure 
along the fibril is the attachment of the sarcolemma in insects’ 
muscle to Dobie’s lines. There is no doubt that this membrane 
dips down and seems prolonged into Dobie’s lines in a most 
beautiful and regular manner. The significance of this is very 
obscure, and is quite beyond me. ‘There are many possibilities. 
It may be, although there is no proof of it, that a membrane 
exists here continuous with the sarcolemma; it may be that there 
is nothing but some cementing substance more soluble in alcohol 
than the sarcous matter; it may be that there is a little minor 
crest at this point to which the sarcolemma is attached. This 
little crest I have certainly seen in some fibres, and it has 
already been figured by more than one writer, yet in others, 
whose outlines are wonderfully distinct, no trace of it is to be 
made out. ‘The fibres can hardly be said to break across in 
the line of Dobie; all that can definitely be affirmed is that 
they cleave in the thinnest part, or the light stripe. The in- 
vestigation of this point is one of great difficulty, owing to the 
haze around the broken points, and I can never make up my 
mind to any definite statement. This transverse cleavage is not, 
of course, a point of very much weight, as the fibre would 
