510 Remarks on the Luminosiiy of ihe Sea* 



motions of fig. /, we are, however, able to supply from 

 analogy some of the deficiencies. Now, it seems certain that 

 the very quick rotatory motion, produced by the fascicles of 

 hairs at the upper and lower extremities, had for its object 

 not only the supply of food, in the manner so well described 

 by Mr. Baird, and which is, in fact, perfectly analogous to 

 what I have observed in the common Branchipus (Cancer 

 Linn.) stagnalis, but also, as in that animal, for the equally 

 important function of respiration ; it being evident that the 

 fascicles at the tail cannot be set in motion for the pur- 

 pose of producing a whirlpool, the centre of which is the 

 mouth, and which is the case with the fascicles at the sides 

 of the head ; those at the tail I should, therefore, rather con- 

 sider as the analogues of the false respiratory legs of some of 

 the typical Crustacea. If we further compare fig. 83. ^ with 

 Dr. Shaw's figure of the young state of the Branchipus stag- 

 nalis, in the first volume of the Linnean Transactions, we 

 find the same short obtuse body, and likewise the three pairs 

 of long lateral fringed legs ; whilst, if fig. 83. i be compared 

 with the figure of the second state of the same animal in the 

 same plate, we perceive in both the tail more elongated, and 

 the long ciliated legs reduced to two pairs. Hence, both 

 from structure and economy, I should be inclined to think 

 that Mr. Baird's two animals belong to that group of 

 entomostracous Crustacea, whose legs serve both for swim- 

 ming and respiration (Branchiopoda), rather than to the 

 Lophyropa or Ostrapoda. The small size of the animal 

 (scarcely that of a small pin's head), and its fascicles of hairs, 

 are different from any of the known forms of the former group. 



In fig. 98. a and b, in the preceding memoir, two lateral 

 eyes are represented ; hence I should regard them as con- 

 generous with fig. 83. d (Vol. III.), rather than e andj^ which 

 belong to the one-eyed genus Cyclops. The only two remain^ 

 ing animals belong to the more perfectly organised Crusta- 

 cea, and appear referable either to the group containing the 

 long-tailed crabs with eyes on foot-stalks (Malacostraca Pod- 

 opthalma, division Macrura), or to the split-legged shrimps 

 (Schizopoda) ; indeed I should be inclined to agree with 

 Mr. J. T. Thompson, that the first of them, at least, belongs 

 to the latter group. 



Fig. 100. a seems to represent Sir Joseph Banks's Cancer 

 fulgens, especially in the antennae. In this respect Mr. Thomp- 

 son's figure of the Noctiluca Banks/? seems to be distinct. 

 As the legs of these animals are always placed in pairs, Mr. 

 Baird has certainly fallen into an error respecting their 

 number : the true legs being stated to be only six, and the 

 abdominal false legs seven. It^ however, this animal belong 



