326 Puget Sound Marine Sta. Pub. Vol. 1, No. 28 



it takes for the fish to come from the shell is very short indeed if it is dis- 

 turbed while hatching, but the time elapsing from the change in the zona 

 radiata until the fish is free is at the most two hours. 



The fish all thrived equally well, whether head, tail or body hatched 

 first. In 82 eggs observed while hatching, 39 emerged from the shell head 

 first and 43 tail first. The observations on the hatching of the Chinook 

 salmon agree very well with those of White (48) on the brook trout except 

 that the change in the zona radiata was not mentioned in that account. 



The pectoral fins begin moving immediately before hatching. In one 

 case the zona radiata was first pierced by the motion of these fins. Just 

 after hatching the young fry lies quietly on the bottom on the side of 

 its yolk sac and remains in that position for some time unless disturbed. 



Fish just hatched lie quiescent on the bottom, only moving when dis- 

 turbed, until the yolk sac is nearly absorbed. A slight jar on the side 

 of the trough or a light tactual stimulus is sufficient to make the young 

 fry move about. 



The fish newly hatched, although possessing correlated muscular 

 movement, is not able to swim in a straight line but swims in a spiral or 

 crooked path when stimulated. The awkward movements of the young 

 fry are due to the large mass of inert material in the yolk sac hanging 

 from the body. 



For about 60 days the developing fry live on food stored in the yolk 

 sac. At the end of the time the yolk sac is absorbed and the fish begins 

 to swim about, dart after food, rise to the surface and display all signs of 

 being ready to feed on food external to its body. 



BIBLIOGRAPHY 



1. Agassiz, A., and Whitman, C. O. On the development of some pelagic 



fish eggs. Proc. Amer. Acad. Arts and Sci. Vol. 12 new Ser., or 

 Vol. 20 whole Ser. 1884. 



2. Balfour, F. Comparative embryology. Macmillan & Co. ; London. 



1885. 

 S. Brooks, G. On the origin of the hypoblast in pelagic teleostean ova. 

 Quart. Journ. Mic. Sci. Vol. 25. 1885. 



4. Chamberlain, F. M. Some observations on the salmon trout in Alas- 



ka. Bur. Fish, of Pacific Coast, Doc. 627. 1907. 



5. Cobb, J. N. The salmon fisheries of the Pacific Coast. Bur. Fish., 



Doc. 751. 1911. 



6. Cunningham, J. T. On the relation of the yolk to the gastrula in 



teleosteans, and in other vertebrate types. Quart. Journ. Mic. Sci. 

 Vol. 26. 1885. 



