ZOOLOGICAL SOCIETY BULLETIN. 



i23 



They come so raj^idlv tliut tlie attendants 

 liave to remove them daily by the bucketful, 

 to large reserve tanks, to prevent overcrowd- 

 ing. Shipments to State lakes have to be 

 made frequently. 



The picture shows a thick swarm of young 

 whitcfish in the middle of the tank, and a mass 

 of yellow perch eggs floating at the top of 

 the hatching jar at the left. The time re- 

 quired for the incubation of the eggs of most 

 of our American trouts varies from forty 

 days in the California rainbow-trout, to 1 25 

 days in the eastern brook-trout, at tempera- 

 tures of 40° to 50°. Spawning ma}' take 

 place from September to May, according to 

 the climate of the locality. 



A notable exception is the spawning season 

 of the black-spotted trout of the Rocky 

 Mountain region, wliich occurs fi"om May to 

 July. This is the only fresh-water species 

 whose eggs arc availai)le for keeping the 

 hatchery in operation during the summer 

 months. 



Tlie time required for hatching eggs of the 

 Eastern salmons is from 157 to 169 days at 

 ;5T r'alir. Eggs of the quinnat salmon of 

 the PaciHc Coast hatch in about thirty-five 

 days at 54°. 



In most trouts and salmons tlie 3'olk sac is 

 absoriied in thirty to forty days ; in the black- 

 spotted trouts the process is faster, being 

 coni])lctcd in about twenty days. 



Whitcfish eggs hatcli in about 150 days at 

 34 ; wall-eyed pike eggs in seventeen to 

 twenty days at 43° ; yellow perch eggs in 

 seven to twenty-eight days and shad eggs in 

 three to ten days at 55° to 65°. Whitefish 

 spawn in November and December, wall-eyed 

 pike in April, and 3'ellow percii in !March and 

 April. Shad spawn from February to July, 

 according to the latitude of the river they 

 enter, which means February in Florida, and 

 July in the New England States. 



There were recently in the Aquarium cjuin- 

 nat salmon hatched from eggs shipped from 

 California to New York by express. The 

 eggs were stripped from the parent fish at a 

 Government hatchery in California, and 

 hatched for fifteen days or until the eye spots 

 appeared in the eggs. They were then 

 shipped in refrigerator boxes, wliich complete- 

 Iv arrested the development until they reached 

 the Aquarium, where about twenty-five days 



more in the hatchery troughs completed the 

 incubation. Some of the large rainbow trout, 

 now in the Aquarium tanks, were hatched in 

 the building five j^ears ago. 



Enormous numbers of fishes can be safelv 

 and cheaply transferred from one part of the 

 country to another, without water, as eggs, 

 while the shipping of live fishes in tanks of 

 water is both uncertain and expensive. 



America leads the world in this modern 

 science, and the Government plants thousands 

 of miUions of young fish in our waters every 

 year. This important work is supplemented 

 by the various State fish commissions through- 

 out the country, which in the aggregate pro- 

 duce nearly as many more. 



WEAPONS OF FISHES. 

 Sword of swordfish, tusk of narwhal and saw of sawfish. 



THE WEAPONS OF FISFIES. 



THE accompanying photograph sliows the 

 sword of the swordfish, the saw of the 

 sawfish and the tusk of the narwhal, 

 three remarkable weapons of marine animals,. 



