202 E - A - Schäfer, 



vary inversely with the size and distinctness of the dots and dis- 

 appear in fibres in which the dots are not seen. 



Marshall's idea 1 ) that the transverse networks are elastic and 

 that they are stretched across the fibre, being attached at its circum- 

 ference to the sarcolemma, is, so far as I can see, a pure hypothesis 

 without any evidence in its favour. That their filaments are not 

 attached to the sarcolemma is shown by Fig. 18, where they are seen 

 to end freely without joining it, and that they have nothing in common 

 with elastic tissue is shown by their extreme affinity for gold. In this 

 respect they resemble nothing so much as the processes of the cor- 

 puscles of the frog's cornea, having, when sufficiently magnified, the 

 same dark, mottled or granular appearance. And if further evidence 

 against this view of Marshall's were necessary, it is to be obtained 

 from the fact that as will be afterwards at greater length made 

 manifest, they do not diminish in thickness with the contraction and 

 bulging of the fibre; but become, on the contrary, increased in thick- 

 ness when a previously extended fibre passes into the contracted or 

 retracted condition. 



The structure of the wing-muscles. 



The consideration of the main question relative to the actual 

 structure of the cross-striated muscles, as compared with their apparent 

 structure, may be said now to be completed. We have arrived, in 

 the foregoing part of this paper, at the conclusion that these muscles 

 are in all cases composed of sarcostyles (muscle-columns), which are 

 separated from one another by intermediate substance or sarcoplasm, 

 this being probably of a protoplasmic nature. There are, however, 

 two important parts of the subject which require to be considered, 

 viz: — the alleged fibrillation of the sarcostyles and the cause or 

 causes of the cross-striation of the muscle-substance. These two parts 

 of the question cannot, however, be fairly approached until the struc- 

 ture of the sarcostyles of the wing-muscles has been subjected to 

 careful investigation. 



*) Op. cit. p. 100. 



