NOTES. 



349 



According to Bulk ("Chemische UntersuchungderKrebsteine:" MUller'a 

 Archiv. 1835), the gastroliths have the following 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 HI., CHAPTER L, 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 a pieds rouges" of France, and not to 

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

 a 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 

 environ," 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, rarely 

 exceeds half this length. 



M. Soubeiran ("Sur 1'histoire naturelle et 1'education des iWevisses:" 

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

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

 following table : 



Crayfish of the year 



1 year old 



2 years old 



3 years 



4 years 



5 years 

 indeterminate 

 very old 



Mean length. 

 Metres. 

 0-025 

 0-050 

 0-070 

 0-090 

 0-110 

 0-125 

 0-160 

 0-190 



Mean weight. 

 Grammes. 



0-50 



1-60 



3-50 



6-50 



17-50 



18-50 



30-00 



125-00 



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



