144 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
at all ; but it cannot be made for many other striated muscle-fibres, in 
which besides the striae Q there are also recognizable, separated from Q 
by isotropic layers, the more strongly refractive finer striae Z, and even 
another set N. The following table contains the results in microns 
for the three insect muscles, of the direct measurement of the distance 
of the strife by the use of the eye-piece micrometer (Zeiss imm. 1/18, 
1 division = 1-08 /x). 
Hydrophilus 
Scarabaeus .. 
Hylobius 
The approximate agreement of these results with those obtained by 
the diffraction phenomena would seem at first to warrant the idea that 
one of the cross striations, either Z (and N) or Q, is without influence 
on the total diffraction effect. Such a supposition, however, is not 
justifiable, and a great mistake would be made if it were attempted to 
draw conclusions from it in the direction of the Abbe diffraction theory ; 
for the diffraction phenomena resulting from the complicated structure 
of insect muscle could hardly be expected to follow the laws of diffrac- 
tion of a simple grating. 
In a grating prepared for the author by Dr. Steeg of Homburg, the 
distances of the dark bands could be varied. This grating consists of 
Fig. 22. 
6 5 4 3 2 10 
o 1 
1 
1 
l 
i 
i 
i 
i 
a 
1 1 
II 
ii 
i 
i 
i 
i 
i 
a 
2 \ 
II 
ii 
l 
i 
i 
i 
i 
a 
3 1 
II 
ii 
i 
i 
s 
i 
a 
a 
4 j 
II 
ii 
i 
i 
i 
i 
a 
5| 
1 1 
1 1 
a 
i 
i 
i 
i 
a 
6| 
1 1 
i i 
i 
i 
i 
i 
7 1 
1 1 
i i 
q 
i 
i 
8 | 
1 1 
i i 
i 
q 
i 
i 
9 1 
1 1 
i i 
i 
i 
i 
a 
10 | 
1 1 
i i 
i 
i 
a 
u] 
1 1 
i i 
i 
i 
i 
a 
12 1 
1 1 
i 
i 
i 
a 
15 1 
1 
i 
i 
i 
l 
two superposed glass plates, each of w r hich carries a fine division in 
0 • 1 mm. The upper plate can be moved over the other by means of a 
micrometer screw, and can also be rotated so as to bring the lines in 
the two plates parallel. Fig. 22 shows the diffraction phenomena 
H. 
ha. 
hi. 
Visible aniso- 
tropic striae. 
7-5 
3-8 
3-5 
Q, Z. 
7 
3-25 
3-75 
Q, Z. 
13-5 
6-5 
7 
Q, N, Z. 
