552 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [28] 



opening in the membrane, and thi£ opening is surrounded by a sticky 

 matter, such as is frequently found on eggs just after they have been 

 laid, and which causes some other fish-eggs to stick to any object with 

 which they come in contact. In the codfish eggs the floating sperma- 

 tozoa enter this matter, some of them reach the small opening in the 

 shell of the egg and through it enter the body of the egg. "What be- 

 comes of them has not been observed in the codfish egg, but from obser- 

 vations made on the eggs of other animals it is known that the sperma- 

 tozoa dissolve inside the egg and assimilate with it. When this has 

 been accomplished, the egg is impregnated, and the young fish begins 

 to make its appearance. If there is no impregnation the egg rots. 



It has also been observed that spermatozoa only enter newly -laid eggs. 

 Even if only half au hour or less has elapsed, the water has produced 

 changes in the egg which make it impossible for the spermatozoa to im- 

 pregnate the egg. But even the spermatozoa do not retain their fruct- 

 ifying power for any length of time after they have been in the water. 

 On this circumstance depends a peculiar and, to the fisherman, very im- 

 portant practice of the spawing fish. Fish spawn either by couples, or 

 groups of three, or whole schools. In the first-mentioned case the male 

 keeps quite close to the female, in order to squirt the milt upon the eggs 

 immediately after the female has spawned. In some fish, for instance 

 the stickleback, this is very noticeable. The male stickleback builds a 

 nest of vegetable fiber among the algae, and when this is finished fetches 

 the female, which enters the nest and lays her eggs. The male impa- 

 tiently waits till the female is done, and finally pushes her out, so that 

 he may enter the nest and impregnate the eggs. This practice can easily 

 be observed daring the months of May and June, for these nests are 

 only a few feet below the surface of the water. 



Other fish do not take such good care of their eggs, but simply lay 

 them and let them sink and stick to the bottom, like the herring, or 

 float about in the water like the codfish. If in this case eggs are to be 

 impregnated, it is necessary that the water be full of freshly emitted 

 spermatozoa. This is probably the reason why these fish are always 

 found in large schools during the spawning season. All through this 

 school the male fish emit their semen, so that the water, as I have myself 

 observed (see Annual Eeport of the Commission, 1S74-'7G, p. 2G), looks, 

 if not white, at any rate quite muddy. In this water the eggs are laid, 

 and are copiously covered with the spermatozoa. If the fish were to 

 swim near the surface in couples the impregnation would be very un- 

 certain, but the larger the school of fish the more evenly will the sper- 

 matozoa be distributed in spite of wind and current. Fish which 

 spawn in this manner must therefore first of all gather in schools. It 

 seems that on reaching the coast they move to and fro for some time 

 (weeks or months), and during this time gather in schools, all of the 

 fish which compose them having about equally-developed sexual organs. 

 This is the reason why the herring fisheries yield such a good income. 

 The fish are so closely massed together that large numbers can be caught 



