204 A HISTORY OF RECENT CRUSTACEA 
Smith has studied its development, and carefully described 
the embryo as it appears some time before hatching, also 
the first, second, and third larval stages, and the first post- 
larval stage. In this genus it appears that the Zoea stage 
—_—> 
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\ \s i ih 7 
Fig.18.— AstacusAmericanus (Milne-Edwards), 
fan early larval form, lateral view [S. 1. Smith]. 
Fic. 17.—Astacus Americanus (Milne- 
Edwards), early laival form, dorsal 
view [S. I. Smith]. 
¥ 
is omitted, as far as the free existence of the animal is con- 
cerned, and that the young one is hatched in the Mysis 
\ A. 
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ii . PRS. Wy 
Fic.19.—Astacus Americanus (Milne-Edwards), third stage [S. I. Smith]. 
form. Professor Smith did not accurately ascertain the 
age of the youngest larvee he described, but supposed them 
to be at most a few days old and not to have moulted more 
