BIOLOGICAL OBSERVATIONS ON THE HERRING. 631 



fresh and healthy for a month. Only where a number of eggs had be- 

 come -pasted together did they begin to mold or rot. Wherever the 

 eggs lay at the bottom of the vessel in a single layer it would not even 

 have been necessary to change the water once a day during the normal 

 period of development. 



In artihcial hatching special care should therefore be taken to distrib- 

 ute the eggs evenly over the vessel. If this is done their sticking to 

 the bottom is no hinderance, but rather an advantage, as the fine sedi- 

 ment which forms at the bottom can easily be removed without injuring 

 the eggs. 



In the following review of the results of my five experiments I have 

 omitted many details, because I would only have to repeat what I have 

 communicated in former publications. 



, Experiment 1. 



From the eggs kept in the open water of tbe Bay of Kiel young fish 

 were hatched in 10 to 11 days. 



This agrees with my former statement (Eeport of the Commission for 

 1877, p. 240) as regards the time required for the development of autumn 

 eggs in water of the same temperature. These required 11 days at a 

 temperature of 10° to 11° 0. (;j0°-51.8° F., and spring eggs, which 

 formed the subject of my present investigation, required abotit the same 

 time, ha'sang during the first day been in water having a temperature 

 of 8.4° (47.12° F.), which afterwards was changed to 11° to 12° (51.8°- 

 53.6° F.). 



The young fish after having left the eggs only differed from those 

 hatched in autumn in being somewhat smaller. Two of the larger ones 

 were measured with the following results (given in millimeters) : 



Experiment 2. 



Placing eggs at the beginning of their development for three days in 

 water having a temperature of 1° to 2° 0. (33.8°-35.6° F.), did not injure 

 them in the least, but retarded the hatching about four to five days. This 

 process of development was therefore not stopped, but merely retarded. 

 This slower development must have continued after the eggs had been 

 replaced in water having a temperature of 11° to 12° (51.8°-53.6 F.). 



In this experiment the time from the impregnation of the eggs till the 

 young fish escaped was fourteen to fifteen days. 



