S" 



ANTS. 



noticed by Furel. In a .similar series of Formica (jlaciaUs (Fig. 29), 

 however, there are no such striking differences in the three phases. 

 The pedunculate bodies ( pb ) are as highly developed in the female as 

 they are in the worker, and they can hardly be said to be vestigial in 

 the male. In I'hcniolc instabilis ( Fig. 30), too, the female and soldier 

 have well-developed pedunculate bodies, though these seem to be insig- 

 nificant in the male. \Yhile, therefore, the male brain in all these 

 species, apart from the huge development of its optic ganglia and stem- 

 matal nerves, is manifestly deficient, I doubt whether we are justified 

 in regarding the brain of the female as being inferior to that of the 

 worker. It is true that the worker brain is relatively larger, notwith- 

 standing the smaller eyes and stemmata, or the complete absence of the 

 latter, but I would interpret this greater volume as an embryonic char- 



D 



FIG. 30. Heads of soldier (A), worker (B), female (C), and male (D} of 

 Pheidole instabilis, drawn under the same magnification, with brain, eyes and ocelli 

 viewed as transparent objects. (Original.) Letters as in Figs. 28 and 29. 



acter. The worker is, in a sense, an arrested, neotenic or more imma- 

 ture form of the female, and it is well known that the volume of the 

 brain and of the central nervous system in general is much greater in 

 proportion to that of the body in embryonic and juvenile than in adult 

 animals. Forel was probably influenced in his interpretation by the 

 view, so long accepted, but now abandoned by myrmecologists, that the 



