PROBLEM 189 103 



Problem j:iS : How fishes are avtifirinlhj jtrojia^atrd. 



Method. — The operations of strippimj can lie demonstrated 

 in the classroom at certain times of the year, oi- if tlic school is in 

 the neighborhood of state or government fish hatcheries,' visit 

 them. Make careful notes on the artificial methotls of raising 

 fishes. Observe especially the equipment of the hatchery tanks, 

 caretaking of fish, etc. (See page 240, Civic Biology.) 



Observations. — Note the stripping of the females for roe (eggs) 

 and the males for milt (sperms). Collect and examine roe and 

 milt under the compound microscope. Which cells are larger, 

 roe or milt? Which are the more active? Why? 



Why are the eggs squeezed into a l)ucket with fresh water 

 and the milt immediately poured over them? 



Why are the eggs then placed in receptacles which have water 

 running through them? 



NOTE. — Fresh-water fishes usually lay their eggs on the bottom of brooks or 

 rivers, sometimes in nests prepared for this purpose. After the eggs are laid the 

 male sprays them with milt. 



In what respects does artificial fertilization resem])le this process? 

 Conclusion. — 1. Write a paragraph on the process of artificial 

 fertilization in fishes. 



2. Which would be a surer method of fertihzation, artificial or 

 natural? Explain. 



3. Of what value is artificial propagation of fishes? 



Problem J39: Trip to the aquarium. (Optional, in place of 

 Problems 133 and 138.) 



Method and Observations. — Select a lively fisli. 



Is the fish protected by form or color? If so, explain how. 

 Show exactly what each fin does for the fish in the proce^^s of loco- 

 motion. Can a fish see? Hear? Smell? (Jive reasons based 

 on your observations. Explain exactly how a fish gets its oxygen 

 in breathing. Make a diagram in your nott^book to illustrate 



1 In place of hatcheries, study figures of the process, for salmon or (rouf. See 

 a Manual of Fish Culture, Department of U. S. Fish Commission for ISOS, Plates 

 16, 28, 34, 53, especi illy for salmon and trout. 



