Muscle- Columns which form the Wing-Muscles of Insects. 283 



through the clear intervals under the microscope, and I was at first 

 disposed to believe that it was confined to the sarcous elements. But 

 the first photograph which was taken showed faintly, but unmistak- 

 ably, that it extended also through those intervals. This can also be 

 detected at certain parts of those photographs which are here repro- 

 duced. The longitudinal striation, therefore, although by far the 

 most marked in the sarcous elements, extends through the whole 

 length of the sarcostyle. It might, therefore, be supposed to represent 

 a fibrillation of the sarcostyle, and this is the view which has been 

 taken by all previous authors who have noticed the appearance. 

 They have supposed the muscle-column to be constituted of a number 

 of juxtaposed fibrils, each of which is composed of successive alterna- 

 tions of the substance composing the sarcostyle, each one, therefore, 

 being composed, in the middle of each segment, of a rod-like portion 

 of the sarcous element ; at either end of this, and continuous with it, 

 of a portion of the substance of the clear interval ; and, lastly, at the 

 ends of the segments, of a portion of the transverse membrane. 

 The sarcons element is, according to this view, formed by the juxta- 

 position of a number of rod-like elements, which are stained by 

 hsematoxylin and similar methods (amongst which must be reckoned 

 this alcohol-gold method) ; the clear intervals being formed of continua- 

 tions of these rod-like elements, which are, however, of a different 

 chemical nature since they do not take these stains, and exhibit differ- 

 ent optical properties ; and the transverse membranes of minute, dot- 

 like elements having, again, different chemical and optical properties 

 from the other parts. (The accessory disks, since they are inconstant, 

 may, in this brief preliminary communication, be left out of account.) 

 But the optical sections of the sarcostyles (figs. 6, 7a, S, and 8a), i.e., 

 more especially of their sarcous elements, which, in teased preparations 

 of muscles prepared by the alcohol-gold method, are frequently set 

 free in the preparation, and are seen lying, as often as not, upon 

 one surface, show conclusively that the above supposition regarding 

 the fibrillar constitution of the sarcostyles is entirely erroneous. 

 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, which sub- 

 stance 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 such canals, and the contents of these 

 canals are, to all appearance, freely continuous with the transpa- 

 rent, colourless substance of the clear intervals ; this can be made 

 out in the longitudinal views. The longitudinal striation of the 

 sarcous element is due to this canalisation ; that of the clear interval 

 to a prolongation of delicate lines (which may, perhaps, represent 



