1908. 



MALFORMED PLAICB. 



163 



"freak" that, at an early stage of its existence, the fish lost the 

 posterior part of its caudal region, at the point now indicated by 

 the truncature on the blind side ; it at once proceeded to repair 

 the injury by producing a secondary terminal fin, viz., the trans- 

 verse fin connecting the dorsal with the anal — similar structures 



en 



being well known in the regenerated tails of some fishes. But at 

 the same time, or soon after, the true tail asserted its rights, and 

 grew again, alongside the secondary fin, and this regeneration 

 would fall under what Prof. Giard has designated as " Regene- 

 rations hypotypiques '■ (0. R. •Soc. Biol. iv. 1897, p. 315), an 



