310 



Transactions . 



(C.) Colour. 



The colour is usually a mottling of green and grey, which harmonizes 

 well with the beds of streams ; some, however, are of a yellowish or a light- 

 brown colour. Those taken from the ponds of the New Plymouth Public 

 Gardens are almost black in colour, and this is no doubt correlated with the 

 colour of the mud on the bottom of the ponds, which Mr. W. W. Smith, 

 the curator, tells me is quite black. Some specimens from the Wanganui 

 Kiver were also very dark. 



It is an interesting fact that now and then a crayfish is met with that 

 is of a bright-red colour, similar to that of a boiled lobster. 



Dr. Marion Newbigin (1898, pp. 117, 129), in her book "Colour in 

 Nature," divides the colours of 'Crustacea into two series, the first series 

 containing the red lipochromes and a yellow pigment, while the second 

 series contains soluble blue pigments. She further shows that there is 

 reason to believe that " when mixed with the yellow pigment, or with the 

 red lipochrome, this blue pigment gives rise respectively to green and brown 

 colours " (p. 129). 



A possible explanation, then, of the occurrence of red crayfish might 

 be that the pigment representing the soluble blue series is absent in these 

 forms. That the blue pigment is the less stable is seen in its disappearance 

 when crayfish are boiled or placed in alcohol. In connection with this, Dr. 

 Newbigin states that in the living animal " the blue or cyanic series occur 

 . . . in solution, while the reds occur in fixed anatomical elements-^the 

 c hromatophores. ' ' 



(D.) Eggs. 



The fresh-water crayfish become sexually mature a considerable time 

 before they attain to their full size. Several ovigerous females were ob- 

 tained which were only 52-5 mm. in length ; but these were from the 

 Khandallah Stream, Wellington, from which no specimens greater than 

 77 mm. were taken. Many of the ovigerous females, however, taken from 

 other districts were not equal in size to the largest specimens from their 

 district. As is to be expected, the number of eggs carried increases in 

 proportion to the size of the crayfish. The accompanying table shows the 



number of eggs carried on some different- sized females :— 



Length of 



Animal. 



Mm. 



57-0 

 66-0 

 71-0 

 76-0 

 90-0 

 96-0 



Number 

 of Eggs. 



23 



26 



56 



60 



72 

 120 

 160 



(E.) Difference noted between Males, Ordinary Females, and Ova/emus 



Females. 



With regard to the relative width of the abdomen in males and females, 

 I found that when trying to pick out the males from the females by looking 

 at them from above I was as often wrong as right. Ovigerous females, 

 however, could usually be detected. Below are given the average propor- 



