118 GEOEGE JOHN EOMANES issi 



No doubt I must in my second book deal with 

 instincts of all kinds, complex or otherwise. Your 

 ' speculations ' on the sand- wasp seem to me very 

 pithy — excuse the pun suggested by the analogy of 

 the cattle — and I think there can be little doubt that 

 such is the direction in which the explanation is to 

 be sought. I also think that the difficulty is mitigated 

 by the consideration that both the ganglion of the 

 spider and the sting of the wasp are organs situated 

 on the median line of their respective possessors, and 

 therefore that the origin of the instinct may have been 

 determined or assisted by the mere anatomical form 

 of the animals — the wasp not stinging till securely 

 mounted on the spider's back, and when so mounted 

 the sting might naturally strike the ganglion. But 

 I have not yet read Fabre's own account, so this 

 view may not hold. Anyhow, and whatever de- 

 termining conditions as to origin may have been, it 

 seems to me there can be little doubt that natural 

 selection would have developed it in the way you 

 suggest. 



I have now grown a number of seeds exposed to 

 the flashing light, but am not yet quite sure as to the 

 result. About one seedling out of ten bends towards 

 the flashing source very decidedly, while all the rest, 

 although exposed to just the same conditions, grow 

 perfectly straight. But I shall, no doubt, find out 

 the reason of this by further trials. It is strange 

 that the same thing happens when I expose other 

 seedlings to constant light of exceedingly dim in- 

 tensity. It looks as if some individuals were more 



