222 



PROCEEDINGS OF THE ACADEMY OF 



[1892. 



tension of myocommata upon the integuments of the body will cross 

 each other and be reinforced at six points in the zigzag transverse 

 course of each rayocorama, viz., twice at each of the points c and c' 

 and along the line a, b, where the middle limb of the -^ rests. 



The only point which now remains to be discussed is the imbrica- 

 tion of the scales. This is also as readily accounted for as the 

 delimitation of the scale-forming areolie, s, s, s, and their tri-linear 

 arrangement in three directions in the convex surface of the integu- 

 ment by means of the mechanical hypothesis here outlined. If we 



/ * J «- J- 6 / f f 



Fig. 2. 



were to make a longitudinal transverse section through a fish along 

 the plane of the letters c, c, c, or c c' d of Fig. 1, we should get a 

 section like Fig. 2 in whicii the myotomes M, M, M, etc., Fig. 2 

 were again found to be V-shaped on either side of the medial axis 

 or vertebral column c, c, Fig. 2. This proves that the myotomes 

 are really cones fitting into one another and that jf we suppose the 

 first one to be inserted into the base of the skull along the line A, 

 B, Fig. 2, that point becomes the anterior fulcrum or 'point d'appui 

 of the whole muscular system. The tensions thus developed upon 

 the skin along the successive myocommata 1, 2, .3 etc., Fig. 2, is 

 such that the integument would be flexed inward opposite each 

 myocomma as shown in the next figure, on a larger scale, which 

 represents the foldings of the integument at the surface of a part 

 of Fig. 2. Here in Fig. 3, the myocommata m, i', m, i', m, etc. 



are seen to be inserted 

 uj)on the internal face 

 of the epidermis ep, ep. 

 The membrane m, m, 

 m, m, acted upon by 

 the muscular fibres of 

 the myotomes IM, ]\[, M, 

 will have the effect of 

 pulling the integument 

 inward in the direction 

 Fig. 3. of the arrows i' , i', from 



the linear points of attachment of the myocommata to the inte- 



