114 MR. R. GURNEY ON LEANDER LONGIROSTRIS 



surprising]y short space of time, probably not more than half a 

 minute, but no doubt there were preliminary movements which 

 were not observed. After the moult the movements are most 

 erratic. The prawn may leap about with violent movements of 

 the abdomen or lie on one side in apparent discomfort, moving 

 its appendages continually. Some hours ehvpse before normal 

 progression is resumed. The very erratic movements immediately 

 after the moult are very likely due in part to the fact that the 

 otocyst is empty, and I was not able to see the process of inserting 

 new grains of sand. The cast skin is often eaten, at least in part, 

 while the newly-moulted prawn frequently falls a victirqi to its 

 companions. 



Breeding females do not, as is commonly the case in Caridea, 

 moult immediately after hatching of the eggs. Both this species 

 and also L. squilla and P. varians moult 4 or 5 days after hatching, 

 but the moult may -be delayed even longer. For example a female 

 about 70 mm. long was taken on July 17, the condition of her 

 pleopods showing that she had recently hatched young ; but she 

 did not moult till August 19, or 33 days later. 



I am unable to say at what intervals adult prawns normally 

 moult, since this can only be ascertained by keeping single 

 individuals for long periods under as nearly as possible natural 

 conditions. Warrington's observations on this point are, in my 

 opinion, quite unreliable, since several prawns were kept in the 

 same aquarium. The female mentioned above moulted a second 

 time on October 5, an interval of 47 days, no growth having 

 taken place. On the other hand, another adult female kept for 

 over a year in fresh water has only moulted once during the 

 whole period. 



5. Pal^monetes varians (Leach). 



Colour. — To the naked eye P. varians is generally almost 

 colourless and translucent, except for traces of yellow-orange 

 colour at the end of the abdomen and on the joints of the legs. 

 Under a lens the whole body is seen to be speckled with small 

 blackish chromatophores. On the thorax these are generally 

 ari^anged in lines, and have a faint yellow halo, while a few pure 

 yellow chromatophores are scattered among them. The rostrum 

 is colourless, except foi- a i-ow of orange-yellow chromatophores 

 below and of black ones along the middle line. The eye-stalks 

 and antennules are richly pigmented. The abdomen is speckled 

 with black and yellow like the thorax, but there is also an orange 

 spot at the junction of segments 4 and 5, and 5 and 6. The 

 uropods aiid telson have orange and blaok spots, but the pleopods 

 are colourless. The chelas of the second legs have an orange patch 

 at the base and at the end of the dactylus, while a similar 

 patch is seen on the merus of the remaining legs. Barrois* has 



* Bull. Soc. Zool. France, xi. 



