350 NOTES. 



NOTE IV., CHAPTER I, p. 37. 

 THE ECDYSES OF CRAYFISHES. 



There is a good deal of discrepancy between different observers as t* 

 the frequency of the process of ecdysis in' crayfishes. In the text I have 

 followed M. Carbonnier, but M. Chantran (" Observations sur 1'histoire 

 natureUedes Ecrevisses :" Comptes Rendus, LXXI. 1870, and LXXII1. 

 1871), who appears to have studied the question (on the "ecrevisse 

 a pieds rouges " apparently) very carefully, declares that the young 

 crayfish moults no fewer than eight times in the course of the first twelve 

 months. The first moult takes place ten days after it is hatched ; the 

 second, third, fourth, and fifth, at intervals of from twenty to twenty-five 

 days, so that the young animal moults five times in the course of the 

 ninety to one hundred days of July, August, and September. From the 

 latter month to the end of April in the following year, no ecdysis takes 

 place. The sixth takes place in May, the seventh in June, and the eighth 

 in July. In the second year of its age, the crayfish moults five times, that 

 is to say, in August and in September, and in May, June, and July 

 following. In the third year, the crayfish commonly moults only twice, 

 namely in July and in September. At a greater age than this, the 

 females moult only once a year, from August to September ; while the 

 males moult twice, first in June and July ; afterwards in August and 

 September. 



The details of the process of ecdysis are discussed by Braun, " Ueber 

 die histologischen Yorgange bei der Hautung von Astacus fluviatilia." 

 Wiirzburg Arbeiten, Bd. II. 



NOTE V., CHAPTER I., p. 39. 

 REPRODUCTION IN CRAYFISHES. 



The males are said to approach the females in November, December, 

 and January, in the case of the French crayfishes. In England they 

 certainly begin as early as the beginning of October, if not earlier. 

 According to M. Chajitran (Comptes Rendus, 1870), and M. Gerbe 

 (Comptes Rendus, 1 858), the male seizes the female with his pincers, 

 throws hei on her back, and deposits the spermatic matter, firstly, on the 

 external plates of the caudal fin ; secondly, on the thoracic sterna around 

 the external openings of the oviducts. During this operation, the 

 appendages of the two first abdominal somites are carried backwards, 



