260 



EDWIN S. GOODRICH. 



stages of development the autenuary segment, together with 

 its appendages, is distinctly post-oral in position, most authors 

 are now agreed that it is a true metamere of primitively post- 



oral origin. 



M. 



Fig. 7. 







'f^ .le. 



M 

 IV 



Fig. 8. 





Fig. 7. — Ventral view of an embryo of Anurida maritima (after Wheeler). 

 Fig. 8. — Diagrammatic plan of the anterior segments of the Hexapoda (the 



numbering of the segments is doubtful, as explained in the text). Ant. 



Antennae. E. Eye. Lb. Labrum. Md. Mandible. il/.r. Maxilla. Pr. I. 



Procephalic lobe. P. Protocerebrum. D. Deutocerebrum. T. Trito- 



cerebrum. Other letters as in Figs. 1 and 2. 



We now come to the first serious difficulty in the interpre- 

 tation of the Arthropod head. In front of the antennary seg- 

 ment, in the embryo Hexapod, extend the large procephalic 



liave examined is provided with a pair of true mesodermic somites and with a 

 pair of appendages, the antennse. Each mesodermic somite sends a hollow 

 diverticulum into an antenna." — Wheeler (18). 



" Uas Cojlomsackclienpaar des Antennensegments wor bei den von mir 

 untersuchten Embryonen stets in typischer Weise ausgebildet." — R. Hey- 

 mons (3). 



