62 LIFE-HISTORY AND DEVELOPMENT OF 



an intimate connection between them and the hordes of jelly- 

 fishes (Aurelia and Cyanea) which abound in the inshore 

 waters towards the end of summer. He thought the young 

 cod approached the jelly-fish for the sake of the minute pelagic 

 animals stupefied by its poisonous threads, and that the fish 

 repaid this favour by picking off a parasitic crustacean (Hyperia 

 medusarum) which clings to the jelly-fish. Observations, con- 

 tinued for a long period in this country, however, show that 

 this connection is only casual and of very little importance, and 

 that certain Hyperice are occasionally found in vast numbers in 

 a free condition. 



As the season advances, the young cod are joined off the 

 rocky ledges by a few pollack and whiting, but not by the 

 haddock, which has certain social views of its own keeping to 

 the deep water farther out. The size of these cod late in autumn, 

 as in October, varies, some reaching from 4 to 5 inches in 

 length. Their food ranges from zoophytes to crustaceans, 

 mollusks, and small fishes, and in confinement the larger are 

 voracious, an example in the laboratory about 5 inches readily 

 attacking a smaller (3 inches) and swallowing it as far as 

 possible, though for some time a considerable portion of the 

 body and tail of the prey projected from the mouth. Moreover, 

 the tessellated condition becomes less marked, and as they 

 approach 8 inches in length a tendency in some to uniformity 

 of tint is noticeable. Many of those, however, that continue to 

 haunt the rocky shores and the tangle-forests beyond low water 

 still retain for some time mottled sides, and they are known by 

 the name of rock-cod. Further, while their growth in the 

 earlier stages is less marked, it is now very rapid even in 

 confinement. The exact rate of growth in the free condition in 

 the sea is difficult to estimate, but the little cod of an inch and 

 a half to an inch and three-quarters in June reach lengths 

 varying from 3 to 5 inches in autumn, and in the tanks of the 

 laboratory, specimens 5 inches in August attain 8 inches the 

 following March. At Arendal, in Norway, where opportunities 

 for watching the growth of cod in confinement have been 

 supplied with a liberality not excelled in our country, Capt. 

 Dannevig found that the cod of 3 mm. in April reached only 



