282 Prof. E. A. Sclmfer. On tJie Minute Struct , t rf of tlir 



entirely of the sarcons elements, which are distinctly bulged, and 

 arranged closely succeeding one another with but narrow clt 

 intervals between them. In these very narrow clear intervals the later 

 ally-stretched and thinned-out transverse membranes cannot be seen 

 unless the sarcons elements are forcibly dragged somewhat apart ir 

 the process of isolating them ; if this is done the transverse nu 

 branes become visible (figs. 2 and 2a). In moderately extende 

 sarcostyles (fig. 5) the sarcous elements are more separated from or 

 another, the clear intervals being correspondingly longer and tl 

 transverse membranes distinct. In greatly extended sarcostyles (figs. 

 and 3a) the sarcous elements are not only lengthened and rauc 

 narrowed, but show a tendency to separate in the middle into 

 halves, leaving a space between them. The clear intervals are 

 lengthened, and the transverse membranes are thickened ; the whol 

 sarcostyle being narrowed. It may be inferred, from the separatk 

 of the sarcous element, that it is really constituted of two halves, wl 

 in the retracted fibre abut against one another in the middle of 

 muscle segment, bat in the extended fibre are separated from or, 

 another. Indications of this separation can be made out even in the noi 

 extended sarcous clement, as in some of those represented in fig. 

 Whether or not there is a fine membrane between the two hah 

 as described by Hensen, my preparations do not enable me to det 

 mine. Nor have I been able to observe in them the farther 

 tion, with still farther extension, of separate disks (accessory dii 

 Nebenscheiben) from the ends of the sarcous elements, a separatk 

 which has been described and figured by several good observers. 



In the preceding statements and descriptions there is nothing tl 

 is altogether novel or that has not been described with sufficit 

 clearness by previous authors. But the application of photograph 

 leaves no room whatever to doubt the accuracy of those descrij 

 tions. 



.There is, however, one essential point of structure which I have 01 

 seen clearly in preparations made by this method, and which is 

 distinctly shown in the photographs. Various authors (Wagem 

 Krause, Kolliker, van Gehuchten), as before said, have described 

 fibrillation of the sarcostyles of the wing-muscles ; or at least a lonj 

 tudinal striation of the sarcous elements, with a dotted appearance 

 the transverse membranes. This striation is very plain in several 

 those wing-sarcostyles which are here photographed, and also in 

 others which are similarly prepared. It is even plainer under 1 

 microscope than in the photographs, because the mass of red-stair 

 substance which forms the sarcous elements allows hardly any actinic 

 light to reach the photographic plate, and the sarcons elements, 

 well stained, look, therefore, nearly uniformly black on the posit ivt-. 

 It is very difficult, however, to trace the longitudinal striatiou> 





