[3] RETARDING DEVELOPMENT OF SHAD EGGS. 789 



rise to 55° which was about 10 o'clock p. m. same date, when a second 

 lot of freshly-taken eggs, of about the same number as the first, was 

 placed in the chest. 



The temperature was then allowed to sink to 48°, and kept there, not 

 running below 47° nor above 49°. About 10 a. m. of the 12th the eggfi 

 of the first lot were found to be all dead and were thrown away, but 

 those of the second lot appeared to contain some good ones, and one 

 trayful was placed in a cone of fresh running water at a temperature 

 of about 750. Un the third day after, or on the 15th of June, about 20 

 or 30 young fish hatched from this lot. 



At 12 m. of the 12th, after the trayful of eggs had been transferred to 

 the cone, a third lot of eggs was placed in the chest. These eggs had 

 been taken on the night of the 11th and kept in a cone of fresh running 

 water until the segmentation cap had entirely covered the yelk and the 

 young fish could be seen as a dark band along the side of the vitellus. 

 The temperature was now allowed to sink to 43^, and kept at about 45^ 

 until 6 p. m. of the 14th, when all the eggs of both second and third lots 

 were found to be dead. Forty three degrees is thus undoubtedly too low 

 a temperature for shad spawn ; otherwise we ought to have had some 

 live eggs in either the second lot, which furnished live ones at 48°, or 

 in the third lot, which had been subjected to the low temperature for 

 only about two days. On June 17th, 10 ji. m., a fourth lot of freshly- 

 taken eggs was placed in the chest, where the temperature showed 64°, 

 and on the 20th a fifth lot was consigned to the well. In these latter 

 ova the young fish were so far advanced as to show the eyes, protover- 

 tebrae, ear-cavity, and the heart as a single-chambered pulsatile organ. 

 When these were placed in the chest the temperature was 55<3, and it 

 was kept at this point until the 23d, when both eggs and young fish 

 were found to be dead. In order to keep the temperature at 55° or5Co 

 very little ice was necessary, and it is possible that the eggs did not 

 have moisture enough to maintain them in good condition, since they ap- 

 peared to melt down into a mat-like mass after being in the chest for a 

 day or so. This was not noticed, or but very slightly, in the other cases. 

 Our only success, or partial success, with the ice-chest, then, was with 

 that portion of the second lot of eggs which was kept at a temperature 

 of 4S°. The young fish which were hatched from these eggs were ex- 

 ceedinglj- vigorous and hearty, and when we broke camp on the 24th, 

 or nine days after they had escaped from the eggs, they were about five- 

 eighths of an inch in length, with the rays of the dorsal, anal, and caudal 

 fins well advanced, the end of the notochord turned up very i^romi- 

 neutly, and the caudal tin slightly forked. They were about one-third 

 larger than some older fish which were in another cone and which had 

 been hatched out in the ordinary manner. In the stomachs of all of 

 these young fish I found a great many shells and remains of daphniae 

 and other small animals, and saw them, and especially the older ones 

 above mentioned, eat the dead of their own species. 



