markings and attitudes of Icpidopterous larvte, 295 



spots have ceased to form any part in the average 

 ontogeny. Nevertheless, when they are present, their 

 variability is so excessive that the various steps towards 

 the disappearance of the system can be made out with 

 a fair degree of probability. It is also likely that the 

 history of the rise in both cases has been similar to that 

 of the decline. Certainly this is true of the head 

 tubercles. They are enlarged and brightly-coloured 

 shagreen dots ; the topmost of each row that forms a 

 yellow margin to the face. This is proved by the hair 

 that still remains on their summits. As they disappear 

 each red tubercle again becomes yellow and similar to 

 the others, except for its greater size. So also the 

 simplest form of the system of red spots is seen in 

 those larvae with a very small patch on each side of the 

 spiracles (except the 1st), and perhaps a small patch on 

 each of the four anterior pairs of claspers. Then we 

 have larvae with these rows formed of large and con- 

 spicuous patches, and with another series of patches 

 above the spiracular row. The spiracles are in all larvse 

 surrounded by a reddish line, and the simplest form of 

 the system seems to consist in a slight peripheral 

 spreading of this colour. These coloured patches consist 

 of modified ground colour, although shagreen dots may 

 be found upon them. The a^jparently uniform occurrence 

 of the patches in the later stages is certainly an argu- 

 ment against my explanation, and is in favour of that 

 offered by Weismann. Mr. William White's observations 

 upon this subject render it probable that the spots often 

 appear at a much earlier date than that at which they 

 were noticed by Weismann. The uniformity of this onto- 

 geny is very remarkable. There is practically no diffe- 

 rence between the first and last stages, except the more 

 obvious hairs and complete subdorsal of the former and 

 the triangular head of the latter. Two of these 

 distinctions occasionally fail, as has been shown. This 

 uniformity may point to very long-continued protection 

 by the existing form of markings. Traces of other 

 conditions are seen in the hairs, head-tubercles, and 

 reddish spots. It will probably be very instructive to 

 examine the hairs of the young larva with fairly high 

 powers. At present I have only used the hand-lens 

 (except in more advanced stages). It will be interesting 

 to ascertain the form of the forked ends of the hairs in 

 the early stages uf, indeed, they are forked at such 

 times). 



