Protocerebnim of Micropteryx. 131 



vordere) root, or else that the posterior branch represents 

 that organ and that the ascending branch is a new organ. 

 The first of these views is supported by the fact that the 

 ascending and posterior branches leave the stem by a com- 

 mon origin, the ascending trmik. On the other hand, so 

 far as our knowledge yet goes there is no other brain in 

 which the backward root is bifurcated, which is what this 

 view implies. 



As I have said, it is also possible to regard the posterior 

 branch as the rucklatifige Wurzel {vordere Wurzel, tiibercule 

 anterieur) and the ascending root as an organ which cannot 

 be homologised with anything yet described. This is quite 

 a rational view to adopt, for practically nothing is yet known 

 about the brain of the Lepidoptera. Personally I do not 

 see any necessity for dubbing this a new organ, but if 

 Kiihnle's identification of the vordere with the riicklaufige 

 Wurzel is proved correct, then we shall probably find it 

 necessary to find a name for what I have provisionally called 

 the ascending branch. An investigation of other types 

 might yield most fruitful results. 



This very small and abstruse point must be settled defi- 

 nitely before the study of insect brains has gone further. 

 Unfortunately it is not possible to attack the question from 

 a comparative standpoint, but it is essential that we should 

 start work with our homologies correctly and clearly defined. 

 There can be no compromise between Kiihnle's view and 

 my own, and the point at issue is fundamental. I consider 

 that there is, at any rate, very little reason for doubting 

 my identification of the innere Wurzel, which agrees with 

 the views of previous writers. 



These conflicting views may be expressed thus : accord- 

 ing to my view, ascending trunk = common origin of — 



1. Ascending branch {vordere Wurzel, etc.) 



= Forward root. 



2. Posterior branch {rucliaufige Wurzel) 



= Backward root. 



Kiihnle, however, asserts that rucldaufige Wurzel=vordere 

 Wurzel. If this is so, then either — 



(i) Ascending trunk and ascending branch and posterior 

 branch together = rucldaufige Wurzel, or else — 



(ii) Ascending trunk = common origin of {a) posterior 

 branch {rucUaiifige Wurzel) and (b) ascending branch 

 (not homologous with anything yet described). 



