128 W. B. DWIGIIT. 



who reported thereon in a paper before the New York 

 Lyceum in October, 1869, and in a published paper in 

 the American Naturalist, vol. iv., July, 1870. 



Prof. D wight discussed the structure and relations of 

 the trilobite, and stated that Burmeister's opinion that 

 it had membranaceous swimmerets instead of stout, 

 chitinous legs, had been, until very recently, the most 

 accepted theory among naturalists. Mr. C. D. Walcott 

 had, however, very lately shown, by comparing many 

 microscopic cross-sections of trilobites, that they proba- 

 bly had spiral gills, and round, strong, and jointed 

 legs. A still more recent discovery of a specimen in 

 Ohio, described in the American Naturalist, December, 

 1883, by J. Mickleborough, which appears to possess 

 legs of this kind, seems to reinforce strongly this theory. 

 This is one of the most interesting iDoints brought out in 

 modern paleontological research. 



It has been stated that among thousands of moulted 

 carapaces of the Limulus, examined at various stages of 

 growth, not one had been found possessing the peculiar 

 nippers of the male. From this fact, it had been concluded 

 that these male appendages did not exist until after the 

 creature had undergone its last moulting. Prof. Dwight 

 had noticed that the nippers of the male were never to be 

 found on any of the young specimens or moulted carapaces 

 which he had examined, and that he had searched in vain 

 for this distinction between the sexes in hundreds of ex- 

 quisitely formed larvae. It therefore seemed to him that 

 the observation was probably correct in so far as regards 

 the earlier stages of the development. That the "king 

 crab' 1 never moults after developing the nipper-claws, is,, 

 however, to say the least, not proven. Professor Lock- 

 wood has attacked this statement, and shown that such 

 moulting may well occur and yet the rejected carapaces 

 may not be found on our beaches. It was suggested that 

 such maturer moulting occurs only in deep waters, be- 

 yond the reach of wave-action. 



so 



