NOTE III., CHAPTER I., p. 31. GROWTH OF CRAYFISH.

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’Écrevisse. Paris, 1869); but they obviously apply only to the large “Écrevisse à pieds rouges” of France, and not to the English crayfish, which appears to be identical with the “Écrevisse à pieds blancs,” and is of much smaller size. According to M. Carbonnier (l. c. p. 51), the young crayfish just born is “un centimètre 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 l’histoire naturelle et l’education des Écrevisses:” 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. Metres. Mean weight. Grammes.

Crayfish of the year 0·025 0·50

Crayfish 1 year old 0·050 1·50

Crayfish 2 years old 0·070 3·50

Crayfish 3 years old 0·090 6·50

Crayfish 4 years old 0·110 17·50

Crayfish 5 years old 0·125 18·50

Crayfish indeterminate 0·160 30·00

Crayfish very old 0·190 125·00

These observations must also apply to the “Écrevisse à pieds rouges.”