194 Annals Entomological Society of America [Vol. X, 



embryonic segment to which the labium is articulated. They 

 must explain why there are six segments in the head, if the 

 sixth or labial segment remains in the neck region behind the 

 head, to form the cervical sclerites. They must explain the 

 presence in the head region of the labial neuromere. They 

 must explain the lack of segmental structures in the neck region 

 if it is really a "labial or microthoracic segment." They 

 must explain why in the neck region alone in the whole realm 

 of Zoology, a pair of appendages have detached themselves 

 from the supposed segment which originally bore them, and 

 have grafted themselves upon another region; and the descrip- 

 tion of the hitherto unknown mechanism by which this unique 

 event was brought to pass, will be a distinct contribution to 

 science! Unless they are prepared to admit that the other 

 intersegmental regions (III and V of Fig. 1) were made to appear 

 to be homologous with the neck plates (region I) merely for 

 the purpose of deceiving the unwary, they must grant that 

 these other intersegmental regions between the thoracic seg- 

 ments are also distinct segments, if they claim that the neck 

 region (with which they are in every way homologous) is a 

 distinct segment, either labial or "microthoracic." They must 

 then explain why these new "segments" have no segmental 

 structures, atid why embryology offers no indication of their 

 segmental nature. Indeed, the difficulties in the way of 

 accepting the view that the neck plates represent a "labial or 

 microthoracic segment" are so numerous and insuperable, that 

 it is astonishing that any one would deliberately adopt such an 

 utterly unfounded hypothesis and disregard the obvious 

 explanation of the neck plates as an intersegmental region 

 between the true labial segment and the prothorax, just like 

 the other intersegmental region between the thoracic segments — 

 a view which, unlike the "labial or microthoracic segment" 

 hypothesis, postulates the occurrence of no hitherto unparalleled 

 phenomenon, involves the operation of no inexplicable mechan- 

 ism, is in complete accord with all of the observed facts of 

 embryology and anatomy, and is the simplest and most logical 

 explanation thus far advanced to account for the occurrence 

 of the neck plates. On this account we are justified in assuming 

 that the neck plates do not represent a segment either labial or 

 "microthoracic," and it is consequently incorrect to designate 

 them as such. 



