272 



U. S. BUREAU OF FISHERIES 



A large information chart placed near the hatchery shows the 

 spawning seasons of fishes and the periods of incubation of the eggs 

 of diifferent species. 



Figure 13 shows some of the automatic hatching jars and their 

 connections with one of the receiving tanks. The flow of water in 

 the jars is so arranged that the young fishes rise to the surface after 



hatching and are 

 automatically floated 

 into the adjacent re- 

 ceiving tanks. 



AN OBJECT LESSON 

 ON MOSQUITOES 



An instructive sum- 

 mer exhibit in the New 

 York Aquarium and 

 cordially approved by 

 the board of health 

 is a wire- screened, 

 8-gallon, round, glass 

 aquarium containing 

 mosquito larvae, with 

 the following label : 



Mosquitoes lay their 

 eggs iu clusters on the sur- 

 face of still water, such 

 as is found in rain bar- 

 rels, cisterns, ditches, 

 stagnant ponds, undrained 

 swamps, and marshes. 

 Each female mosquito 

 lays from 150 to 400 eggs, 

 which, in about a week, hatch into larvre or " wrigglers." About a week later 

 the " wrigglers " become mosquitoes. The mosquito is the only known source of 

 malaria and yellow fever. If the breeding places of mosquitoes can be oblit- 

 erated, malaria and yellow fever can be wiped out and annoyance from 

 mosquito bites avoided. 



Fig. 15. — Mosquito larvae 



RESERVOIR FOR SEA WATER 



Sea water, as used in American and European aquariums, is 

 stored in underground reservoirs adjacent to or underneath the 

 aquarium building. It is used as a "closed circulation," being 

 pumped continuously to the distributing levels, whence it flows to 

 exhibition tanks and filters and finally back to the reservoir. The 

 filtration process that keeps it clear eliminates, of course, whatever 

 minute forms of marine life it may have contained originally. 

 Moreover, it is kept in the dark to prevent the growth of algse. 

 There is some loss through evaporation and leakage, which is made 

 up from time to time by small additions to the original supply. 

 The increase in salinity resulting from evaporation appears to be 

 negligible. After years of service the stored supply suffers little 

 deterioration if properly managed. There is an increase in its 

 acidity, resulting from the wastes from the numerous animals that 



