NOTES. 849 
According to Dulk (‘‘Chemische Untersuchung der Krebsteine:” Miiller’s 
Archiv. 1835), the gastroliths have the following composition :— 
Animal matter soluble in water 7 - 11°43 
Animal matter insoluble in water (probably chitin) 4:33 
Phosphate of lime . . Fi . 3 ° . 18°60 
Carbonate of lime A ‘ a . . » . 63°16 
Soda reckoned as carbonate . . . . » 141 
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, CHarrer 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’ Kerevisse. Paris, 1869) ; but they obviously 
apply only to the large “ Ecrevisse 4 pieds rouges” of France, and not to 
the English crayfish, which appears to be identical with the “ Ecrevisse 
a4 pieds blancs,” and is of much smaller size. According to M. Carbonnier 
(1. ce. p. 51), the young crayfish just born is “un centimétre 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 Vhistoire naturelle et l’education des Hcrevisses :” 
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 : 
Mean length. Mean weight. 
Metres. Grammes. 
Crayfish of the year . . 0°025 . . 0°50 
»  lyear old . . 0:050 . . 1:50 
»  2yearsold . - 0070 . . 3°50 
»  3Syears ,, . fs 0-090 ° . 6°50 
»  ‘A&years ,, s . 07110 . . 17°50 
» years ,, - «© 0125 . . 1850 
» indeterminate . 7 0-160 : . 30°00 
» very old . 0-190 a - 125:00 
These observations must also aly to the “Herevisse 4 pieds rouges.” 
