Feb. 12, 1880] 



NA TURE 



!55 



the five pairs of walking and nipping legs). But no such 

 realisation of the ideal can be found in Astacine nature, 

 any more than in that of the higher Catarrhines. In 

 some crayfish more or less of the leg-gills are suppressed ; 

 in others, the body-gills ; in others, the joint-gills ; and so 

 ringing the changes on the combination of these elements, 

 it is possible to construct clearly-distinguished groups 

 amongst the crayfishes of many climes, which at first 

 sight seem to differ very little from one another. Further, 

 Prof. Huxlev shows that crayfishes and lobsters difter 

 from prawns, shrimps, and crabs, in having villous gills 



instead of laminated gills, in being " trichobranchiate " 

 in place of " phyllobranchiate." 



It will probably not be welcome news to some of our 

 readers that the English crayfish is in all probability not 

 entitled to the current title olAstacus Jluviatilis. This name 

 appears to belong to a larger species, sometimes called A. 

 nodi/is, hardly distinguishable from the English one, which 

 in France lives side by side with it. The smaller crayfish, 

 which alone occurs in England, is known as A. torn/ilium. 

 This specific title will, it is to be feared, have to be adopted, 

 although it by implication casts a slur upon the River 



■j>il\2 



Fig. 5. 



Fig. 4. 



F.g. 4-Camiarw clarkii. male ('. nat. s.rc), after Ih s ™. Fre %.— Abacus fimiatitis.-\n A. ths gi , ' -anclibstegite, 



are seen ia their natural p siuon ; in U, the podoOrancMiB are rem .ved, and the anteri r set of arlbrobranclua: turned downwards (~ 2 ). 1, eye- 

 stalk; a, antennule: 3, antenna; 4 . mandible; 6. scaphognathite ; 7. first maxillipede, in B the eoipoiite, o which the hue paints, is partly rem , ved : 

 . ro.forceps; 14, fourth ambulatory leg ; 1^. first abdominal appendage; xy. hr,t. and ::v... second abd ..inal 

 somite : 1W* 8. art. 9, art. 13. the posterior arthrobranchux of the second and third maxillipedes and of the th.rd ambul.u Ty leg ; art . 9. arb . 13. the 

 ant. ani of the third ambulatory leg ; fid. 8, podobranchiae of the second maxillipede ; pbd. 13, thai 



the third ambulatory leg ; plb. 12, plb. 13. the two rudimentary pluurobranchiae ; ; " 



the' functional pteurobranchiae ; r, rostrum. 



/sis. A . jluviatilis has red tips to its legs and a rostrum 

 which differs by a notch or two from that of A. tor- 

 rentium. Further, and this is very curious, A. torrentiilm 

 never has been found to be infested by that very interest- 

 ing parasite (more interesting even than the crayfish 

 itself), the crab-leech, Astacobdella, or Branchiobdella, 

 whilst it is quite abundant on the A. Jluviatilis, at any 

 rate in some rivers {e.g., the Saale, in North Germany). 



A. Jluviatilis is largely eaten in France, attaining to the 

 very respectable size of 5 inches or so in length, whilst our 

 smaller A. torrentium is neglected from this point of 

 view. We can recommend it, however, when boiled in 

 salt and water, as nearly if not quite equalling the prawn. 



The poisonous properties of the flesh of crayfish might 

 perhaps be considered as justly falling within the scope 

 of the first chapter of Prof. Huxley's treatise. As in the 

 case of many mollusca and some true fishes, there appears 

 to be a substance present which acts as an irritant poison 

 upon the human organism, and to its action so ne persons 

 are more liable than are others, whilst certain conditions 

 of the crayfish seem to favour the development of a large 

 amount of this poisonous body. A case was recently 

 reported in a French medical journal, of the poisoning of 

 six persons who partook of a dish of crayfishes — in one 

 case with fatal result. 



E. Ray Lankester 



FOGS 



of our genuine London log which at times condenses to 

 a consistency so thick as to give point to the sketch in 



THERE are fogs and fogs, — from the one extreme of Punch some years ago, representing a street-boy springing 

 the dry fog of continental meteorologists which into the air, exclaiming " I am monarch of all I survey." 

 merely blurs the sky with a bluiah-tinted mist and shears Fogs appear under widely different conditions. Thus 

 the sun of its brilliancy as it nears the horizon, so that the J the waters of the Arne occasionally appear for some dis- 

 eye can look on its disk undisturbed, to the other extreme tance after issuing from their icy cavern, like a steaming 



