A NATURAL PUZZLE 227 



waters, the ClienirpJalus ecliinidentus of Michael Sars, 

 and CherapJiilus negledus, G. 0. Sars. The last-named 

 author, however, has quite recently been able to make 

 a very unexpected contribution to the settlement of the 

 question, for, in examining the development of different 

 members of the family, he has found that the various 

 genera and species are often more strongly distinguished 

 in the larval forms than in the adults, so that the 

 hesitation felt about separating, for example, the species 

 Crangon vulgaris and Crangon Allmanni, or tlie "genera 

 Cheraphilus and Pontopltilus, can no longer reasonably be 

 persisted in. Cheraphilus, it may be mentioned, agrees 

 with Crangon in having five pairs of branchiae attached 

 respectively to the five pairs of trunk-legs, but Pontophilus, 

 while agreeing with Cheraphilus in the shortness of the 

 second legs, differs both from it and Crangon in having six 

 pairs of well-developed branchias, besides a rudimentary 

 pair on the second maxillipeds. Since the species Egeon 

 fasciatus, Risso, has been provided by nature with a re- 

 markable brown band across the fourth segment of the 

 pleon and similar colouring on the tail-fan, as if to sepa- 

 rate it unmistakably from all other species, and to enable 

 the collector to identify it without further trouble, it may 

 be well to notice that Cheraphilus negledus also has a deep 

 brown band across the fourth segment of the pleon and a 

 narrower one across the tail-fan, so that after all the col- 

 lector has need to be cautious. 



The arctic Sahinea septeincarinata (Sabine) agrees with 

 Fontophilus in the branchial formula. In describing it in 

 1821 Sabine calls attention to the fact that the second legs 

 are ' unarmed,' that is, simple or not chelate, and, while 

 recognising that this is an ' essential point ' of distinction 

 from the known species of Crangon and Fontophilus, he 

 enters one of the common but always useless protests 

 against the multiplication of genera. If he spoke thus in 

 1821, what would he have thought in 1891 ? Kroyer, 

 who redescribed the species in 1842, after stating that it 

 is very abundant at Spitzbergen, adds that he had found 

 the stomach of the seal Phocci harhata quite filled with it. 

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