CRUSTACEANS 



Pasiphaeidae, is made the subject of the following note in the Fauna of 

 Liverpool, ' This, which appears to be a rare British species, has been 

 given to me by a Dee fisherman. All the Hoylake men know it, and say 

 that they may, on an average, meet with one in a week. The specimen is in 

 the Royal Institution Museum.'^ That the naturalist should prize one prawn 

 above another because it comes more seldom into the net, is a species of 

 idolatry or form of foolishness which the ordinary fisherman is very unwilling 

 to encourage. Mr. A. O. Walker also records P. sivado from the ' Mouths 

 of the Dee and Mersey, scarce.' But if every fishing boat finds on an 

 average one every week, the scarcity for scientific purposes is rather artificial 

 than real. From the shrimps and from one another the three prawns above 

 named are easily distinguished. The shrimps alone have the first pair of 

 legs sub-chelate, by which is meant that the penultimate joint or ' hand ' is 

 not produced into an elongate process or ' thumb ' more or less parallel with 

 the last joint or ' finger." The finger folds down on the distal margin of the 

 hand. In Pandalus montagui the first legs are provided with minute chels. 

 In Leander the nippers are well developed, and in Pasiphaa they attain a 

 conspicuous length, both finger and thumb being strikingly denticulate along 

 their confronting margins, with curved apices which cross one another when 

 the chela is closed. This species, like the shrimps, has an insignificant 

 rostrum, while both the other prawns are armed with a long dentate frontal 

 horn. In general aspect all the three differ among themselves considerably, 

 owing to the superior size of Leander serratus and the singular lateral 

 compression of the Pasiphaa. From the family Hippolytidse Messrs. F. W. 

 Keeble and F. W. Gamble attribute more than one species to this county. 

 Part of their work on the colour physiology of Hippolyte varians (Leach) 

 was done at the Piel Laboratory, and they say, ' Hippolyte varians is one of the 

 few Crustacea which may be considered abundant in the neighbourhood of 

 Piel. It keeps for the most part to beds of weeds below low-water mark, 

 and hence its habits have largely to be learnt from specimens in captivity.' 

 They found that ' fresh weed or the dead bodies of its fellows serve Hippolyte as 

 food.' In the Barrow Channel, they say, ' Shades of brown and yellow are abun- 

 dant, whilst green and red are sometimes common, sometimes rare. With the 

 large Halidrys siliquosa a dark brown variety is associated ; among the fine 

 Polyzoon {Bowerbankid) which clothes the lower parts of the Halidrys stems, 

 a speckled variety of Hippolyte occurs : in the tide-pools of Foulney Island the 

 green variety, and it alone, is found among the Zostera^ As a result of their 

 experiments they say, ' We have arrived at the conclusion that there are two 

 colour-phases in Hippolyte varians; one diurnal, the other nocturnal. The 

 recurrence of these phases is to some extent independent of the conditions of 

 illumination, although the colour itself may be profoundly influenced by 

 varying the quality and intensity of the incident light, and also by other 

 stimuli, which do not act through the eye.' Lastly they say, ' The species 

 of Crustacea we worked with have been kindly identified by A. O. 

 Walker, Esq. From the very limited fauna of Piel shore it may be of 

 interest to gwQ the list, which, however, is not quite complete. Hippolyte 

 varians (Leach), common, just below the level of ordinary spring tides. 

 Hippolyte fascigera (Gosse), a doubtful species; almost certainly a variety of 



1 Op. cit. S3- 



,163 



