THE SHARKS AND RAYS 107 



the rest, is in the habit of rising to the surface in warm weather 

 and chasing the pilchards, more after the manner of sharks. 

 This may or may not be true, but it is easy to account for the 

 belief on the ground of confusion between two separate facts. 

 On the one hand, large thornbacks are certainly seen from time 

 to time at the surface of the sea, and this is most probably 

 connected with either some sudden atmospheric change with 

 which we are unacquainted, or it may even have something 

 to do with the breeding arrangements. On the other hand, 

 pilchards have undoubtedly been found inside thornbacks. 

 The two statements, taken separately, are above suspicion, 

 and the danger only arises when they are associated as cause 

 and effect, and some one then infers that because the thornback 

 sometimes swims at the surface, and because also it sometimes 

 devours pilchards — therefore it must have captured those 

 pilchards at the surface. Not only do we know for a fact 

 that pilchards, though commonly surface-feeders, are in the 

 habit of swimming close to the bottom, near the ordinary 

 haunts of the rays, in certain conditions of weather and 

 temperature, but this shark-like method of preying on 

 surface-swimming forms is absolutely contrary to what might 

 be expected of the thornback's structure and ordinary mode 

 of life. To make the positive assertion that this ray could 

 not, taking into consideration the position of its mouth, 

 capture a pilchard swimming at high speed and close to the 

 surface, would be to fall into a dogmatic habit that has already, 

 in the case of the whale and thresher story, been deplored. 

 At the same time, in the absence of ocular evidence of rays 

 chasing surface-fish, some doubt may be allowed to rest on 

 the theory. 



Like most rays, the thornback deposits oblong egg-purses, 

 and allusion was made on an earlier page to their lack of 

 anchoring threads, such as we find in the eggs of the nurse 

 and rowhound, and to Mr. Dunn's theory of the compensating 

 adhesive substance. 



