268 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



whether these, even if different, produce the same perfect in- 

 sects or different ones. The attempt at discriminating from 

 the perfect insect alone he considers extremely unsatisfactory. 



THE KING-CRAB NOT A CRUSTACEAN. 



Professor Van Beneden, who has been lately studying the 

 embryonic development of the common American king-crab 

 (Limulus polyphemus), comes to the conclusion, first, that 

 these are not crustaceans, as none of the characteristic phases 

 of the development of Crustacea can be distinguished ; and 

 that, on the other hand, their development shows the closest 

 resemblance to' that of the scorpions and other arachnids. 

 Second, that the affinity between the limuli and trilobites can 

 not be doubted, and that the analogy between them is the 

 greater in proportion as we examine them at a less advanced 

 period of their development. Third, that the trilobites, as 

 well as the Eurypterida and Pcecilopoda, must be separated 

 from the class Crustacea, and form, with the arachnids, a dis- 

 tinct division. 13 A, January 15, 1872, 30. 



HAVE TRILOBITES LEGS? 



The question as to whether trilobites possessed legs or not 

 is one that has been discussed of late quite extensively. Pro- 

 fessor Dana, Professor Smith, and Professor Verrill, of New 

 Haven, have taken the ground that the animal was without 

 these appendages. Mr. Henry Woodward, of the British 

 Museum, however, on the strength of specimens collected by 

 Mr. E. Billings, of Montreal, insisted that the animal had real 

 legs. To this Professor Dana rejoins that a renewed exami- 

 nation by himself and colleagues only tends to confirm them 

 in their previously expressed opinion, that the arches which 

 were supposed to carry the legs are so slender as to be inca- 

 pable of bearing the free legs of so large an animal, the diam- 

 eter of the joints being hardly more than a sixteenth of an 

 inch outside measure, consequently affording insufficient 

 room inside for the required muscles. Legs of such propor- 

 tion, according to Professor Smith, do not belong to the class 

 of crustaceans. He also thinks that the regular spacing of 

 these arches along the under surface renders it very improb- 

 able indeed that they supported legs. If crowded together 

 the argument would be of less weight, but while they are so 



