236 E. A. Schäfer, 



Description of the figures on Plates XV, XVI and XVII. 1 ) 



Fig. I A. Extended leg-muscle fibre of Dytiscus marginalia, living. «, dim band: 

 b, bright band showing double rows of dots which are the optical section 

 of the transverse networks shown in the cross section (Fig. 2): c, inden- 

 tation of sarcolemma at the bright band; e, longitudinal lines of sarcoplasm. 



Fig. 1 B. A contraction wave in a leg-muscle fibre of Dytiscus. C, contracted 

 part of the fibre; Ft, extended or resting part; P, part passing into or 

 out of contraction. «, />, c as in Fig. 1; a' «', dim bands (in P) becoming 

 encroached upon by bright bands //, //; b", b", (in C) bright bands now 

 occupying the entire interval before occupied by bright and dim bands; 

 c' (in P), sarcoplasm accumulating in the situation of the double rows 

 of dots of R; c", c'\ (in C), the accumulations of sarcoplasm which form 

 the dark bands of the contracted fibre. 



Fîg. 2. Transverse section of leg-fibre of Dytiscus, made whilst frozen and exami- 

 ned without addition of fluid. Three nuclei with their connecting proto- 

 plasm occupy the middle of the section, from this protoplasm lines of 

 sarcoplasm radiate towards the sarcolemma with oblique communications 

 here and there, giving the appearance of a network with radial meshes. 



Figs. 1 A and B and Fig. 2 were drawn from the living specimens, under Hart- 

 nack's No. 11 immersion objective. They are copied from the Philosophical 

 Transactions for 1873. 



Fig. 3. Leg-muscle of Locusta, showing a large amount of interstitial substance 

 or sarcoplasm between the muscle-columns or sarcostyles. Acid-preparation. 



Fig. 4. Amoeboid white corpuscle of Triton, killed instantaneously by steam, 

 fixed by alcohol and stained with haematoxylin. The nucleus with its 

 chromatic reticulum is well seen. The protoplasm around the nucleus 

 (spongioplasm) has a granular or reticular look : the peripheral and pseudo- 

 podial protoplasm is quite homogeneous and structureless (hyaloplasm). 



Fig. 5. Leg-muscle of Bombns showing the appearance of a living fibre at three 

 different focal planes. A, superficial focus, showing double rows of dots 

 in the clear band as in Fig. 1 : B, middle plane of the fibre exactly 

 focussed, showing the line of central nucleated protoplasm and the double 

 rows of dots replaced by lines ; C, deep focus showing the appearance of 

 a single dotted line in the middle of the clear band. 



Fig. 6. Leg-muscle of Forficula, resting and somewhat extended (vinegar, safranin). 



Fig. 7. Leg-muscle of Harpalus ruficornis, partly contracted (vinegar, safranin). 



') Except when otherwise stated, all the figures have been drawn under 

 Zeiss" 2 mm 1.30 aperture apochromatic homogeneous immersion, with No. 8 or 

 No. 12 compensating ocular. Those which are marked with the magnification are 

 traced from photographs; the rest are not to scale. Fig. 38 is diagrammatic in so 

 far that I have attempted, not very successfully, to express the appearances of 

 different foci in partial perspective. All the other figures were as nearly as I could 

 draw them exact representations of the preparations. 



