XMVJ2. 



[Contributions from the Limnological Laboratory of Cornell University Ithaca, N. Y. 



A Preliminary Study 



of the Distribution, Food and reproductive Capacity 



of some fresh-water Amphipods. 



By 

 George C. Embody. 



With 1 plate and 5 Text-figures. 



Contents. 



I. Introduction. — II. Relative sizes of forms studied. — III. Distribution about Ithaca, 

 New York. — IV. Food. — V. Reproduction: 1. Period. 2. Mating: a) Method; b) Dura- 

 tion. 3. Oviposition and Fertilization. 4. Number of eggs. 5. Period of Incubation. 

 6. Young: Activities and Relation to Parent. 7. Recurrence of the Reproductive Acti- 

 vities. — VI. Moulting of Adults. — VII. Moulting of Young. — Vin. Method of 

 Moulting. — IX. Growth. — X. The Progeny from a Single Pair in one Year. — 

 XI. Enemies. — XII. Summary. — Bibliography. 



I. Introduction. 



The present paper deals with the activities of four locally common 

 species of amphipods representing two different families and three genera, 

 namely: 



I. Family, Gammaridae 



1. Gammarus fasciatus Say. 



2. Gammarus limnaeus Smith. 



3. Eucrangonyx gracilis (Smith). 

 n. Family, Orchestiidae 



4. Hyalella knickerbockeri (Bate). 



With the exception of one blind species these are the only amphi- 

 poda known to occur in the vacinity of Ithaca. 



The observations were made upon individuals in their own native 

 environments and likewise upon others placed in balanced aquaria 

 furnished with characteristic vegetation and from which all natural 

 enemies had been eliminated. The investigation was begun with the 

 ultimate purpose of securing sufficient data to show the practicability 



Embody, Amphipods, Biol. SuppL, III. Serie, 1911. 1 



( 



