224 PROCEEDINGS OF THE ACADEMY OF [1892.. 



still conform to the lines of tension of the linear attachment of the 

 myoconimata to the integuments. The hypothesis may also be 

 extended so as to consistently consider such forms as the pipe fishes 

 and other anomalous forms, where sluggish habits coupled with the 

 almost exclusive use of the dorsal fin in swimming, has rendered 

 the lateral musculature of the body comparatively subordinate in 

 function, and which may even lead to secondary fusion of somites 

 and the consolidation of consecutive pairs or triplets of vertebral 

 centra into single vertebral bodies. 



Two conclusions of prime importance may be drawn from the 

 hypothesis and the evidence here presented, namely : 



1. The scales of fishes bear a segmental relation to the remaining 

 hard and soft parts, and are either repeated consecutively and in 

 oblique rows corresponding to the number of segments, or they may 

 be repeated in rows as multiples of the somites, or segmental reduc- 

 tion may occur which may affect the arrangement of the scales so as 

 to reduce the number of rows below the number of somites indicated 

 by the other soft and hard parts. 



2. The peculiar manner of interdigitation of the muscular somites, 

 as indicated by the sigmoid outline of the myocommata, as seen 

 from their outer faces, and the oblique direction of the membranes 

 separating the muscular cones, has developed a mode of insertion 

 of the myocommata upon the corium which has thrown the integu- 

 ment into rhombic areolae during muscular contraction. These 

 areolae are in line in three directions and the folds separating them, 

 particularly at their posterior borders, are inflected in such a manner 

 by muscular tensions, due to the arrangement of muscular cones, as 

 to induce the condition of imbrication so characteristic of the 

 squaination of many fishes. 



