THE YOUNG OF THE CKAYFISHES ASTACUS AND CAMBAKUS 39 



This larva buried itself in the ooze but was so active as to be caught with 

 difficulty. By October 20, it had shed and grown to a length of 34 mm., with 

 antenna 32 mm. long, so that with the food that had been given it it had 

 gained 4 mm. in length in eighteen days. This larva lived till February, 1905, 

 and died when nine months old. 



Another lot of larvae kept in running water from July 16 to October 2, also 

 yielded but one survivor which had increased from less than 26 mm. to 55 mm. 

 and had a telson-fan 25 mm. wide, thorax 13 mm. wide, and antenna 36 mm. 

 long. This fine young crayfish five months and a week old looked like the adult 

 and was a male with well formed male stylets upon its first abdominal somite. 

 The body was opaque and dark ; greenish-blue and brown finely speckled ; the 

 legs lighter; the chelae with much blue and with the conspicuous flesh-colored 

 area that the adult has at the angle of the claw. The posterior edge of the 

 carapace was dark blue and the antennae were bluish at the base fading to 

 brownish at the tip. The under side of the body was pale flesh-color, or color- 

 less with some clear blue. 



A third lot of larva 1 , 13 mm. long on May 27, and in the third stage, were 

 kept in more favorable conditions, that is, running water in a large tank, with 

 mud, plants, and sunlight, and on October 2 there were six survivors. The 

 measurements of these larvae, five months and a week old are given in the table 

 below : 



Larva A B C D E F 



Length 56 60 63 58 58? 52 



Width 13 15 15 15 15 14 



Antenna length ... 51 52 52 50 55 45 



Sex $ 9 9 9 9 3 



The males A and F had well formed male organs upon the first abdominal 

 somite while the four females had no appendages there, but the largest females 

 B and C had two blue spots upon that somite that suggested some connection 

 with a possible appendage. The colors of these large young were those of 

 adults, and though all reared in the same tank they showed individual differ- 

 ences in : general color, some being more dark olive, others brown ; in size and 

 color of the spot at the angle of the claw, which in one was reduced to a mere 

 light nodule and in others was a very large area; in color of under side of 

 claw which was dark or else bright flaming-red. 



The eight young reared to an age of five months and one week thus 

 measured 30, 55, 56, 60, 63, 58, 58, 52 or an average of 54 mm. 



Tabulating the facts above recorded as to the size and length of duration 

 of the larval stages as far as they were followed we find the following: 



