EXPLANATION OF PLATE XXXVII. 



Fig. 1. — Ventral view of grasshopper, showing heart-tube and some of 

 the tracheal tubes in place in the chitin, but all other systems are 

 removed, a, Air-sacs; h, heart-tube; t, tracheal tube; m, alary mus- 

 cles, showing attachment; s, muscles connecting segments of abdomen. 



Fig. 2. — Histological cross-section through heart, a, Alary muscles; b, 

 fibrous layer; c, connective-tissue or pericardial cells; d, connective- 

 tissue cells; e, ganglion-cells (?) ; /, muscle of heart; h, heart cavity; 

 t, tracheal tubes; i, nerve-like cells. (Chrome-oxalic fixative, Nissl 

 stain). 



Fig. 3. — Longitudinal section of heart with corresponding structures la- 

 beled same as for figure 2. (Formalin fixative, iron-haematoxylin 

 stain.) 



Fig. 4. — So-called ganglion-cells. Same as e, figures 2 and 3. (Formalin 

 fixative, iron-haematoxylin stain.) 



Fig. 5. — Pericardial cells, enlarged. Same as c, figures 2 and 3. 



Fig. 6. — Connective-tissue cells enlarged. Same as d, figures 2 and 3. 



(Figures 5 and 6, chrome-oxalic fixative, Nissl stain.) 

 Fig. 7. — a, Cross-section of heart-muscle (/, of figure 2) ; 6, single fiber 



from cross-section of heart. (Figure 7, a and b, foi-malin fixative, 



iron-hasmatoxylin stain.) 



Fig. 8. — Longitudinal section through heart-muscle (/, figure 3), showing 

 fibers and nerve-like cells (n) . (Stain and fixative same as for fig- 

 ure 7.) 



Fig. 9. — Section through a thoracic ganglion. (Van Gehuch ten's fixa- 

 tive, Nissl stain, with erythrosin for a counter-stain.) 



