NOTES AND MEMORANDA. 459 



the back, fhe sides being spotted or blotched with the same colour, 

 while there are light markings similar in position to the white mark- 

 ings in the specimen described above, but yellow in colour, with 

 brown spots scattered over them. 



The occurrence of red specimens is mentioned by Day, who de- 

 scribes a male specimen of a brilliant carmine colour with white 

 markings. My specimen was a female, so that the colour has 

 nothing to do with sex. We have received several other specimens 

 of the same red colour, but only the one above described has been 

 yet subjected to careful observation. 



It is evident from the above that the red colour is not permanent, 

 so that red specimens do not represent a colour variety ; the red 

 colouration is evidently a temporary condition due to the action of 

 light. Whether an ordinary shore specimen can be made to turn 

 red by being exposed to light reflected from red surroundings has 

 not yet been proved, but it has been shown that a red specimen 

 soon loses its peculiar colour under the conditions above described. 

 At the same time the change is not very rapid ; in the above case 

 it occupied more than a month. It seems probable that the red 

 colour in nature is determined by the fact that the fish lives among 

 red seaweeds. Probably in this case there is no alteration in the 

 quantities of the differently coloured pigments in the skin, but 

 merely an alteration in the expansion and contraction of the differ- 

 ently coloured chromatophores. — J. T. Cunningham. 



Palaemonetes varians in Plymouth. — The estuary of the river Plym 

 is connected, especially upon its left (eastern) side, with a number of 

 small tributaries, whose waters are, even at their mouths, of very low 

 density. In many of these tributaries Palsemonetes varians ahoundis. 

 I have examined especially a large number of individuals from a 

 stream which runs through Saltram Park, in the water of which I 

 have found variations in density ranging from I'OIO to 1*018. 

 From the position of the stream it is improbable that its density is 

 ever much greater than 1*018, though a continuous rain might 

 possibly reduce its specific gravity to a limit below I'OIO. 



The variability of the adult individuals from Saltram is very 

 great. The following statement of variations observed in the 

 characters of the rostrum will show how enormously the variations 

 in this race exceed those indicated by the current diagnoses of the 

 species. 



Among 915 individuals of both sexes — 



The apex was simple in 432 cases. 

 The apex was bifid in 483 „ 



NEW SERIKS. VOL. I, NO. IV. 34 



