430 EEPOET OF COMMISSIONER OF FISH AND FISHERIES. 



show no symptoms of lethargy in water kept at 45'^, while the shad are 

 most active between 68° and 72°, and become torpid and sluggish at a 

 temperature below 65°. 



In the case of the shad there are many indications that the develop- 

 ment of the spawn within the ovaries is hastened by the heat and re- 

 tarded by the cold. In a warm season ripe spawners are more numer- 

 ous early iu the season than in a cold one, and the period for obtaining 

 them is apt to close earlier. 



A temperature in the water of about 75° or 70° seems to be the most 

 favorable for obtaining and hatching spawn. At 80° the eggs hatch 

 very rapidly, but the young fish do not do so well, and a more serious 

 difficulty is the fact that many spawners are taken with the eggs dead 

 in the ovaries ; that is, they have lost entirely the capacity for fecunda- 

 tion, and as there has been no instance of this kind reported when the 

 ■water was below this temperature, it is probably correct to attribute 

 the cause to the high temperature of the water. 



The temperature of the water regulates the period of development of 

 all fishes' eggs that have been experimented with. In the shad-eggs 

 the period required for release of the fish from the eggs was, with an 

 average temperature of 64°, though actually varying between 62° and 

 68°, about seven days. With an average temperature of about 65°, ac- 

 tually between 62° and 69°, the time was about six days. With an av- 

 erage temperature of nearly GQ'^, actually between 62° and 69°, the time 

 for the most of the fish to be free was about five days. An average of 

 68°, between 66° and 75°, released them in about tliree days. An aver- 

 age of 72°, really between 65° and 80°, released the fish in about sev- 

 enty hours, the shortest time observed for a large quantity of eggs, 

 though usually some were hatched a few hours before the majority, and 

 a few eggs lingered for several hours after the eclosion of the rest. 



7. — THE OVARIES AND OVA OF THE SHAD. 



The ovaries of the shad are familiar to eaters of shad-roe, as thej^ are 

 usually cooked whole. They differ from those of the white-fish {Core- 

 goniis alhus) in being shorter in proportion to their length, and the mem- 

 brane of the ovaries is thicker and* stronger, while the white-fish, 

 unlike the shad, has the entire length of each divided transversely into 

 folds, which, on removing the outer membrane, are found to hang sus- 

 pended from the long thickened fold of the membrane on the dorsal 

 side of the ovary, an arrangement that facilitates the passage of the eggs 

 toward the walls of the ovaries, before they fall into the cavity of the 

 abdomen. 



The eggs remain in a compact solid mass until they ripen. At first 

 minute, and the ovaries occupying but a small space in the abdomen, 

 they gradually increase until the whole abdomen is distended with their 

 bulk. On a close examination, as they approach the time of spawning, 

 there will be found the maturing eggs, the larger, which are rather 



