THE KEAKING OF SEA-FISH LARV^. 83 



the same routine was continued in the treatment of the fry in my 

 absence, and two survived the forty-fourth day (September 30th) when 

 they, with the survivors from D and H, were merged together into the 

 jar devoted to this last-mentioned experiment, the conditions of which 

 appeared to be more suitable than plunger-jars for the later stages of 

 development. 



During the course of this experiment the larvae throve splendidly 

 during the first few weeks, up to a length of about 10 mm., and com- 

 pleted all the essential structural changes in their metamorphosis, the 

 permanent fins having been formed and the skeleton established. 

 They were always very lively, and darted about after Copepods with 

 great agility, displaying much pertinacity and considerable acrobatic 

 powers in their efforts to secure their prey. 



Their methods of hunting were always alike, and were so eminently 

 characteristic as to merit a brief description. Upon noticing some 

 fancied morsel, the larva would immediately become transformed with 

 excitement, and, keeping its face constantly towards the object, would 

 commence a series of evolutions, the first purpose of which was to 

 investigate the nature of the prey, and the second to circumvent the 

 latter's escape. Wheeling round through the quadrant of a circle by 

 a series of strokes of the tail, aided by synchronous movements of the 

 pectoral fins, the larva, if satisfied with the result of this preliminary 

 survey, would leap smartly round from side to side of the chosen 

 morsel until by a well-directed forward dart the quarry was seized 

 or frightened away. If the attack were successful, the larva would 

 swim quietly about again; but if unsuccessful, it would swiftly pursue 

 and repeat the same process until success rewarded its efforts or the Cope- 

 pod finally escaped. The pectoral fins were ceaselessly employed in these 

 movements, whether from side to side, up and down, or even backwards. 

 Under these circumstances Mr. Holt's suggestion* that the large size of 

 the pectorals in these larvte may be of merely ancestral significance 

 appears unnecessary. It is true, as my colleague remarks, that these 

 fins are not very effective organs of locomotion, so far as pace alone is 

 concerned ; but it is impossible to spend any time in watching these 

 larvae hunting for food without forming the conviction that the fins are 

 particularly adapted to enable their possessors to cope with the peculiar 

 dodging movements of the Copepods they pursue, which resemble to 

 some extent the well-known tricks of the so-called hovering flies of our 

 gardens and hedge-rows (fam. Syiylddcv). 



Resuming my narrative, however, the fry, in later stages, after the 

 third week, did not as a rule appear to do so well in this jar as those in 

 jar H, to be described below. They continued to grow rapidly, but 



* Journ. M. B. A., v., 1898, p. 123. 



p 2 



