A COMPARATIVE STUDY OF STRIATED MUSCLE. . 31 
A Comparative Study of Striated Muscle. 
By 
William A. Haswell, WH. A., D.Se., 
Lecturer on Biology, University of Sydney. 
With Plates LV and V. 
THERE are very many discrepancies between the statements 
which we find in the writings of various observers as to the 
distribution of striated muscular fibres in the various classes 
of Invertebrata. These discrepancies are due partly to defective 
methods of investigation and misinterpretation of the appear- 
ances observed, but partly also to the want of a distinct under- 
standing as to what constitutes ‘striation’? in muscle. 
Clearly our conception of striation in muscular fibres is derived 
originally from the study of the tissues of the voluntary 
muscles of Mammalia and the Frog, and the limb-muscles of 
Insects, since it was in these that the striation was first 
observed, and it is in these that the nature of striation has 
been invariably investigated. Now what are the essential 
characteristics of striated fibres in such instances? They are 
five in number. 
1. A striated muscular fibre in these cases consists of a 
bundle of narrower elements, the fibrils, which are capable by 
certain methods of treatment of being isolated from one 
another. 
2. The whole substance of the fibre is composed of two series 
of transverse segments, the anisotropous and isotropous series, 
differing in optical properties and affinity for certain dyes, 
which alternate with one another, the segments of the one 
VOL, XXX, PART 2,—NEW SER. Cc 
