BULLETIN OP THE UNITED STATES FISH COMMISSION. 



27-, 



7.". 



An investigation of the conditions other than temperatnre which 

 modify or influence the rate of development in the eggs of shad and 

 other species of fish would furnish the subject of a fruitful biological 

 study, which would probably have important practical applications. 



[n .Table III, prepared by W. F. Page, superintendent of propaga- 

 tion, Central Station, will be found a very interesting summary, giving 

 the average period of hatching under different temperatures from 53.5° 

 to 75.5°. From this it will be seen that while there is considerable 

 variation in the period of hatching in different jars under the same con- 

 ditions of temperature, yet the average time of incubation at a given 

 temperatnre is longer the lower the average temperature prevailing 

 during incubation. 



Table III. — Summary of the period of incubation of 485 jars of shad eggs hatched at, Central 

 Station. U. S. Fish Commission, during 1883, 1884, and 1885. 



The above 485 jars represent a total of 34,323,000 shad eggs. 



All who have been connected with the work of shad production have 

 had occasion in different seasons to note the variations in the date 

 when we first begin to get ripe eggs in any quantity, in the date at 

 which production reaches the maximum for the season, and in the 

 period at which the season closes. This is instructively shown by W. 

 F. Page in Table VI. It will be seen from that table that the season of 

 1885 was remarkably late. No eggs were taken up to April 25. On the 

 corresponding date in 1884 the aggregate collected was 2,240,000, and 

 in 1883 1,3G5,000. The season of 1884, which yielded the largest num- 

 ber of eggs, terminated on May 24, while the seasons of 1883 and 1885 

 extended to June 8. 



