114 Mr. W. M. Dobie on the Minute Structure and 
this arises from the extremely small size of this space, especially 
when the fibril is in a relaxed condition, and is more particular 
found in the examination ofthe muscular fibrils of fish, lobster or 
crab, in which indeed this line can be very rarely seen (fig. 7 ). 
Hence most probably the reason why Mr. Bowman does not re- 
present it. In such cases the only way to obtain a view of it is 
by stretching the fibril when in a perfectly fresh state; this 
cross-line of the clear space in the lobster partook more of the 
nature of a band, in the cases where I was enabled to examine it 
(Pl. VII.fig. 7a). Inthe fish (salmon) I have only seen it ina 
few cases, but in these the appearance was so distinct as not to 
leave the least doubt of its existence. 
I am not aware that this cross-line in the lobster, salmon, skate 
and frog has been seen by any preceding observers. In the pig 
and human subject it has been seen; I have also distinetly ob- 
served it in the muscular fibrillze of the ox. 
The length of the dark and clear spaces is sometimes identical ; 
-at other times, and more frequently, the clear space is shorter ; 
and in the lobster and salmon is often so narrow as to be dimi- 
nished to a somewhat dark hne when the fibril is in a perfectly 
relaxed condition. 
I have also frequently observed, in dissections of the muscular 
fibrillee of the frog and salmon, an appearance which I consider it 
important to mention, the true explanation of which I am at pre- 
sent unable to decide upon. It isas follows :—At the point where 
two fibrille are separated from each other, extended for a greater — 
or less distance between them, there often exists a beautiful ho- 
mogeneous membrane, (resembling the web between two of the 
toes of a duck,) which js stretched by the violence used in the 
separation of the fibrille (fig.8 a). Insome recent observations 
which I have made on the muscular fibres of the skate when 
perfectly fresh, this appearance invariably presented itself, with 
this peculiarity however, that instead of being perfectly homoge- 
neous, it was marked with stripes corresponding to the dark 
and light spaces of the fibrille between which it was stretched 
(fig. 8 5). 
I ef at first inclined to regard this membrane as a shred of 
the sarcolemma accidentally stretched out between two fibrille; : 
but from its being of a decidedly more delicate nature than that 
membrane, and from its being present in nearly every part of 
some preparations, I am inclined to consider it as being caused 
by some homogeneous connecting medium spread among the 
fibrillee. 
The strize in this membrane in the skate I am at a loss to ac- 
count for ; perhaps from the tearmg of the membrane over the 
