THE STUDY OF FRDSH-WATfiR ANIMALS. 183 



be followed as far as possible on the aquarium inhabi- 

 tants. Points of importance which should be emphasised 



are : 



Is there a metamorphosis in the life-history ? 

 Are all stages aquatic in habit ? 

 Compare breathing organs in young and adult. 

 Compare locomotor organs in young and adult. 

 Compare feeding habits of young and adult. 

 If a terrestrial type, what adaptations to aquatic life are 

 apparent ? 



3. Study of activities of the inmates, e.g. of their 

 methods of locomotion, respiration, feeding, etc. (This is 

 in part dealt with under 2.) 



4. Relation of inmates of the pond to each other, e.g. 

 as hunters and hunted. This may be studied incidentally 

 in connection with the consideration of their feeding 

 habits, e.g. in noting the carnivorous forms. In general 

 there are three types, viz. Carnivorous, Vegetarian, and 

 those feeding on dead or decaying stuff, viz. the scavengers. 



5. Relation to, or effect of diverse physical conditions, 

 e.g. light, or temperature; show how alterations disturb 

 the balance of life, or rate of growth. Illustrations of 

 simple experiments under this head are the keeping of jars 

 of small animals, e.g. water-fleas or tadpoles in light and 

 warm places, and dark and colder places respectively. 

 Care must be taken that all other conditions, food, water, 

 etc., are the same. After a time compare growth in the 

 case of the tadpoles, numbers in the case of the water- 

 fleas. Similar experiments may be performed with the 

 feeding of tadpoles or other young animals. Different lots 

 of tadpoles may be fed on vegetable matter, particles of 

 fish, bread, or flesh, and the results noted in the growth 

 and in the time taken for the complete metamorphosis. 



6. Lastly, pupils also should classify the inmates of the 

 aquarium. 



