ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
587 
a. Insecta. 
Minute Structure of Muscle-columns in Wing-muscles of Insects.* 
— Prof. E. A. Schafer has made a study of the muscle-columns, or 
sarcostyles, as he prefers to call them, of the wing-muscles of Insects. 
For the more or less cylindrical disc which forms the dark band the 
author retains the name of “ sarcous element ” ; the fine line which 
bisects the light band he terms the “ transverse membrane,” while the 
light space which separates the ends of the sarcous elements from the 
transverse membranes may be called the clear interval ; it corresponds 
with the isotropous substances of authors. The segment of a sarcostyle 
comprised between two transverse membranes may be termed muscle- 
segment or sarcomere. Prof. Schafer finds that the sarcous elements 
are not made up of a bundle of rods, but are formed of a continuous 
substance (sarcous substance), staining with haematoxylin and with gold 
after hardening in alcohol ; this substance is pierced by tubular canals 
which open at each end of the sarcous element, and in its middle abut 
against one another at the plane of Hensen’s line. The optical section 
of each sarcous element shows a dozen or more of these canals, the 
contents of which are, apparently, freely continuous with the transparent, 
colourless substance of the clear intervals. The longitudinal striation 
of the sarcous element is due to this canalization ; that of the clear 
interval to a prolongation of delicate lines of the sarcous substance 
through the clear interval to the transverse membranes. The whole 
sarcostyle seems to be inclosed by a membrane of extreme delicacy. 
Prof. Schafer has been able to take photographs of his preparations 
which illustrate these points with great clearness. 
If this view of the structure of muscle be accepted it is possible to 
form an idea of what happens when the muscle contracts or extends. In 
the latter case the sarcous elements are narrowed and laterally com- 
pressed by the extending force, and the fluid which is contained in their 
canals is squeezed out and passes into the clear intervals ; furthermore, 
the process of extension elongates the sarcous elements and separates 
them further from the transverse membranes. When, on the other hand, 
the extended sarcostyle is retracted, the sarcous elements swell and the 
clear intervals become shortened so as eventually almost to disappear. 
This can only be effected by absorption of the homogeneous substance 
of the clearer intervals into the sarcous elements ; in all probability it 
is imbibed into the canals or visible pores of the sarcous substance. 
The author believes that the structure of the wing-muscles of insects 
furnishes the key to the comprehension of muscular structure in general, 
and that comparisons may be drawn, detail for detail, between them and 
the more intricate structures seen in Vertebrates and elsewhere. 
Origin of the Blood and Fatty-tissue in Insects.f — Prof. V. Graber 
discusses the complex tissue found in the body-cavity of most insects. 
It includes (1) blood-corpuscles, (2) the fatty-body, (3) the yellow 
“ oenocytes,” which Wielowiejski finds to be usually arranged in seg- 
mental groups, and (4) the pericardial cells which lie near the dorsal 
vessel. All these Graber would include under the title “ haemosteatic 
tissue.” From sections of the young larvae of Stenobothrus , he finds that 
* Proc. Roy. Soc. Lond., xlix. (1891) pp. 280-6 (2 pis.). 
t Biol. Centralbl , xi. (1891) pp. 212-21. 
