1916 



Smith; on Salmon Development 



105 



were not all spawned at the same time. These conditions would not de- 

 tract from the value of the experiment as the eggs were so thoroughly 

 mixed that both baskets would be equally affected. The fish began to 

 leave the shells within two days of the time the eggs arrived at the hatch- 

 ery on the campus. The separation into two groups did not take place 

 until November 29, at which time 12 fish were hatched. These 12 are 

 not counted in the table below. In table 17 is recorded the date on which 



Table 17. The rate of hatching of humpback salmon in darkness 



and light 



Totals 



787 



87 



983 



87 



the count was made, the number hatched between the times of counting, 

 the number of dead removed and the temperature of the water in degrees 

 centigrade. 



The number in the dark trough was 874; the number in the light 

 one, 1,070. Table 17 shows that those in the light hatched more 

 quickly than those in the dark, at least during the early period of hatching. 

 During the first five days of hatching after December 1, 10.18 per cent of 

 the fish in the dark hatched out, while 21.12 per cent of those in the light 

 hatched out. Those in the light were observed to free themselves quickly 

 from the shells and pass through the wires of the basket to the bottom of 

 the trough; on the contrary, those in the dark showed no disposition to 

 escape quickly from their shells, and many of them were observed to be 

 lying quietly half in and half out of the shell. Soon after the baskets 

 were removed, which was done December 29, those in the light began to 

 struggle up stream and maintained a position as close as possible to the 

 upper end of their compartment; but those in the dark showed no dis- 

 position for some time to leave the bottom at the lower end of the trough, 

 where the water drifted them. 



At the time of the closure of the yolk-sac slit a careful weighing was 

 made of 114- fish from the light trough and 108 from the dark. These 

 fish were taken at random by a single sweep of the net from each trough. 



