84 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



Mackerel — The mackerel, too, be found to have the same characteristic, 

 the eggs of both species being found far out at sea. In both cases the 

 e oo- was provided with a small globule of oil, apparently for the express 

 purpose of facilitating its suspension in the water, and which was con- 

 tained in the abdominal sack of the young fish in hatching, and con- 

 st it uted a large part of its embryonic nutriment. 



Plaice. — The eggs of the plaice, too, one of the principal flat-fish of 

 Europe, were found floating freely in the sea, and the inference was 

 drawn that most of the flat-fish family, including the turbot, sole, &c, 

 possessed the same characteristics. An analogy in the habits and phys- 

 iological condition of other species of the cod family, such as the had- 

 dock, the pollock, and the hake, also induced Sars to include them in 

 the same category. 



As a general rule, the eggs of fish that float freely in the sea are 

 single, and belong to the so-called dry eggs, or lack the glutinous en- 

 velope which is found in the case of the herring and some less impor- 

 tant fish, which causes them to adhere to each other in masses and to 

 any other object with which they may come in contact. The herring is 

 almost the only sea fish of economical importance that exhibits the last 

 mentioned characteristic. (Deep Sea Fishing, p. 42.) 



Many forms of animal life, including fishes of the various Antennarius, 

 Chironectes, &c, live habitually in mid-ocean, especially among the 

 masses of floating sea-weeds, of which some species actually make nests 

 in which their eggs are introduced. 



The rate of growth of the young fish varies with the group. In Crys- 

 tallagobius, according to Collett, and perhaps in other forms, the capac- 

 ity of reproduction is developed in a year's time. For the most part, 

 however, it is thought that the ordinary fishes require a period of three 

 or four years before they are able to propagate their kind. It is likely 

 that the sharks require a still greater allowance, although nothing defi- 

 nite is known on this subject. 



The actual rate of growth of the individual varies with the species, 

 and probably to a certain extent with the individual, and the average 

 at maturity varies very much with different so-called schools. Thus 

 among the codfish, a school of mature fish coming in to the coast of 

 New Jersey and elsewhere on the south side of New England, may aver- 

 age not more than 5 to 10 pounds, while another school, which visits 

 Cape Ann for the same purpose, averages a much greater weight, indi- 

 viduals of even 100 pounds not being extremely rare. The same dif- 

 ference in the size of cod occurs elsewhere, as also in that of other 

 kinds offish. What causes this difference it is, of course, impossible 

 to say. 



MaDy fishes experience curious changes of shape and color during the 

 breeding season. These alterations are very much marked in the sal- 

 mon, the male of which develops a lengthened, hooked jaw, in which 

 formidable teeth make their appearance. A common alteration consists 



