1896.] Entomology. 333 



the external incisor, which was first pointed out by Cope, ami which 

 has been observed independently by several others, is frequently 

 observed in Europe as well as in America ; second, that the loss of the 

 first inferior incisor is also not very uncommon in Europe and that the 

 final reduction of the inferior incisors, shciihl it lake [.lace, will be by the 

 loss of this tooth and not by that of the external incisor as in the supe- 

 rior series. He, therefore, believes that the ultimate formula of the 

 incisive dentition in man will be I{, and not I*, as Cope left it. 



ENTOMOLOGY. 1 



The Segmental Sclerites of Spirobolus.— The structure of 

 the segments of Diplopoda has long been a morphological puzzle. On 

 account of the possession of two pairs of legs they have in a general 

 way been supposed to be double segments, that is, formed by the coal- 

 escence of two distinct embryonic or theoretical segments. Toward a 

 morphological demonstration of this idea there has been little progress. 

 Indeed, there are many facts which give grounds of suspicion as to its 

 correctness. Among these may be noticed that the double footed state 

 does not occur in the embryo at all, and that the segments which in 

 the adult bear two pairs of legs either do not exist in the newly hatched 

 larva or do not bear any legs at that stage, the newly hatched diplopod 

 larva having but three pairs of legs, the posterior of which is attached 

 to the fourth segment (at least in the Polydesmoidea). Moreover, all 

 Diplopoda have apodous segments not differing otherwise from those 

 which bear legs; also all Diplopoda have segments which bear but one 

 pair of legs, and yet have not been found to be greatly different from the 

 others. Growing Diplopoda acquire segments by intercalation in front 

 of the last. The segment is added at one moult, the legs for it at the 

 next. As the possession of two pairs of legs has been the occasion of 

 the theories of duplex segments, these facts are the more relevant as 

 objections, since more difficulties are introduced than are disposed of 

 by the theories. 



The existence of plurrc in the Oniscomorpha has long been known, 

 and for a less period in the Coloboguatha and Limacomorpha. In the 

 other orders these elements of the segmental ring are so thoroughly 

 coalesced or eliminated that their existence was theoretical until their 



1 Edited by Clarence M. Weed, New Hampshire College, Durham, N. H. 



