28 Mr. E. B. Poulton's notes ujjon the colours 



been chiefly formed from the study of this species. But I 

 have been long familiar with the coloured spots upon larvae 

 of ^S', ocellatus and S. jJojndi, and I am perfectly convinced 

 that, in these species at any rate, they have nothing to 

 do with coloured borders to the oblique stripes. It is 

 quite possible that they afford protection by resembling 

 galls : — seen irregularly, as they are, between the leaves 

 and upon a ground colour very much like the under 

 side of the leaves (see the Editor's notes lo the trans- 

 lation of Weismann's book). But I do not think that 

 we can yet speak of their significance with any certainty. 

 The spots are excessively variable in size, in the number 

 found in each row, and in the number of the rows them- 

 selves. In these facts we do not seem to recognise the 

 slow but sure accumulation of favourable variations by 

 natural selection. I think it is probable that we see the 

 decline of an old rather than the establishment of a 

 new character. In fact the extreme variability of the 

 spots, when present, seems to be best explained by 

 reversion, which is often unequal and irregular in its 

 action. It should also be remembered that a decided 

 majority of the larvse of S. populi, and an immense 

 majority of S. ocellatus, have no trace of these markings. 

 Shortly after reading Weismann's Essay I was fortu- 

 nate enough to find a spotted variety of S. ocellatus 

 (August 18th, 1883). The larva was feeding on Salix 

 cinerea by the banks of the Eiver Cherwell. It had the 

 bright yellowdsh green ground colour, and each of the 

 spiracles was, as usual, encircled by a fine red line. The 

 following is an account of the number and arrangement 

 of the spots (see PL I., fig. 1) : — Each of the spiracles of 

 segments 5 to 11 (inclusive) was upon or near a red 

 patch, very slightly indicated on segments 5 and 11, 

 and not greatly developed on the others. Except in the 

 smallest instances, each spot was made up of two 

 patches, one anterior and the other posterior to the 

 spiracle, with its encircling red line. There was also a 

 row of spots above and below that just described, and 

 the spots of both were approximately alternate with 

 those of the latter, and therefore each spot of the 

 highest row was situated vertically over one of the 

 lowest, as far as the two rows corresponded. There are 

 only four spots in the lowest row (on each side of the 

 body), one upon each of the first four claspers ; while 

 in the highest row there are distinct spots on the 7th, 



