NOTES. 



349 



According to DulkC'ChemischeUntersuchungderKrebsteine:" Mutter's 

 Archir. 1835), the gastroliths have the follovping composition : — 

 Animal matter soluble in water . • . . 11"43 

 Animal matter insoluble in water (probably chitin) 4'33 



Phosphate of lime 18"60 



Carbonate of lime 63'16 



Soda reckoned as carbonate . . . . . 1 "41 



98-93 



The proportion of mineral to animal matter and of phosphate to car- 

 bonate of lime is therefore greater in the gastroliths than in the exo- 

 skeleton in general. 



Note III., Chapter I., p. 31. 

 GROWTH OF CRAYFISH. 



The statements in the text, after the words " By the end of the year," 

 regarding the sizes of the crayfish at different ages, are given on the 

 authority of M. Carbonnier (L'Ecrevisse. Paris, 1869) ; but they obviously 

 apply only to the large "Ecrevisse k pieds rouges" of France, and not to 

 the English crayfish, which appears to be identical vrith the " Ecrevisse 

 k pieds blancs," and is of much smaller size. According to M. Carbonnier 

 (1. c. p. 51), the young crayfish just born is " un centimetre et demi 

 envii-on," that is to say, three-fifths of an inch long. The young of the 

 English crayfish still attached to the mother, which I have seen, rai-ely 

 exceeds half this length. 



M. Soubeiran (" Sur I'histoire naturelle et I'education des i^crevisses :" 

 Comptes Eendus, LX. 1865) gives the result of his study of the growth 

 of the crayfishes reared at Clairefontaine, near Eambouillet, in the 

 following table : 



Crayfish of the year 



1 year old 



2 years old 



3 years „ 



4 years „ 



5 years „ 

 indeterminate 

 very old 



These observations must also apply to the " Ecrevisse a pieds rouges." 



