THE YOUNG OF THE CRAYFISHES ASTACUS AND CAMBABUS 9 



in lack of abdominal appendages on the first and sixth somites, and in various 

 proportions. 



In America Hagen ('70) in his fundamental study of our crayfish observed 

 the young of Cambarus attached to the mother in alcoholic specimens and re- 

 corded the dimensions of young in which the sexes were externally recogniz- 

 able. Prom like specimens Faxon ('85) in his revision of American crayfish 

 was able to make a number of comparisons with specimens of young Astacus 

 pallipcs from France, and also to demonstrate the important facts that the 

 young Cambarus agreed, in general, with Astacus as described by Huxley, but 

 that in the early larva as in the adult, Cambarus showed no vestige of the gill 

 found on the last thoracic somite in Astacus. These facts were verified by 

 Steele ('02), who for the first time described living larvae of Cambarus hatched 

 from eggs in the laboratory and also recorded facts as to the habits and sizes 

 of young larvae. From like living material Andrews ('04) added details of 

 hatching and behavior of these larvae with figures of side views of living larvae 

 in the first and in the second stages and noted the occurrence of two successive 

 attachments of the larva? by means of special structures. 



To complete that last preliminary paper by adding details and many new 

 facts observed in Cambarus and to describe similar stages in our American 

 Astacus is the purpose of the present paper. 



III. ASTACUS LENIUSCULUS. 



As far as known, no observations have been made upon the life histories 

 and habits of any American crayfish of the genus Astacus and as the following 

 facts were gained from animals kept in Baltimore far from their native habitat 

 they will need the corroboration of future studies made in the Pacific States, 

 but for the present they supply all our knowledge of the young of American 

 Astacus. 



The material for study of the young Astacus was obtained as follows : Sixty- 

 four specimens were received February 23, 1904, by express from Portland, 

 Oregon, and, though packed only in wet excelsior, ten females and eighteen males 

 survived the journey and lived in running water in the laboratory for some 

 time. Shipped without selection of sex, the sixty-four were found to be made up 

 of thirty-one females and thirty-three males, which indicates an equal distribu- 

 tion of the sexes. The males, however, seem to have endured the journey better 

 than did the females. 



During March, April, May, and June these crayfish died slowly one by 

 one, leaving one survivor in October. As they were fed from time to time with 

 small oligochaatae, with fragments of crayfish and with pieces of frogs, the 

 cause of the very slow and lingering deaths was not evident, but probably the 

 food was not sufficient for such large and active crayfish. 



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