158 College of Forestry 



Another pond-snail, Galha catascop'mm, when young (June 

 and July), inhabits the thick algae at depths of from six to 14 

 feet, but when adult migrates to the shore and lives on the 

 boulder and gravel bottoms of the exposed points and shores. 

 It requires at least two years to complete its growth, for adults 

 were observed on the rocky shores in July. The tadpole snails, 

 Physa warreniana and Physa integra, also live in algae at 

 depths down to 10 and 11 feet when young (July), but migrate 

 to the shore when approaching maturity (August and Septem- 

 ber), zvarreniana to inhabit (usually) rocky shores in shallow 

 water, and integra the more quiet and protected habitats near 

 the shore or surface. Lynincea stagnalis lilliance probably 

 exhibits the same migration with age and season as do the 

 other species mentioned, as adults are found only in the late 

 summer and fall on the rocky shores. Half grown individuals 

 were common in July on the boulder shores of the lake. Plan- 

 orbis binneyi has been noted when young among algae in five 

 feet of water in July. In September adults are abundant in 

 shallow water on rocky shores, in company with Lynincea and 

 Galba. 



Additional field study will add to our information concern- 

 ing this matter ; but the examples cited are sufficient to clearly 

 indicate a definite habitat relation between age, season and 

 migration. This relation has been studied only through July, 

 September and a part of October and it is highly desirable 

 that early spring as well as some winter studies be made. 

 Spring studies are especially desirable to determine the length 

 of life of the different species of mollusks, many of which may 

 live but a year, the stock being renewed annually. Definite 

 information as to what species are annuals, biannuals, trian- 

 nuals, etc., would be of much value in estimating the amount 

 and rate of production of food for fish and other animals. 



Adequate information is lacking concerning the periods of 

 egg-laying among the dift"erent species of mollusks in our lakes 

 and ponds. In Oneida Lake during the month of July the eggs 

 of Amnicola, Gillia, Physa, and Lymncca were noted. The 

 ^gg cases of Amnicola covered algae, bottom debris, vegetation, 

 and their own as well as the shells of other species of mol- 



