234 Studies in the Theory of Descent. 



after fourteen days (beginning of July) the young 

 larvae emerge. These are also of a light green 

 colour, and are conspicuous for the great length 

 of the caudal horn, which is nearly half as long as 

 the body. This horn is likewise of a light green 

 at first, but becomes dark violet in the course of 

 an hour. No trace of any markings can be 

 detected at this stage. 



As soon as the caterpillars are hatched they 

 commence to nibble the empty egg shells ; then 

 they run about with great activity, and after 

 several hours take up their position on the largest 

 vein on the under side of the lime leaves, where 

 they remain for a long period. In this situation 

 they have the same form and colour as the leaf- 

 vein, and are very difficult to discover, which 

 would not be the case if they reposed obliquely or 

 transversely to the vein. In about 4 5 days 

 the caterpillars undergo their first moult, and 

 enter upon the second stage. On each side of 

 the segments n 4, there now appear seven 

 oblique whitish stripes on a somewhat darker 



only, on the other. Of the three species discussed by Dr. 

 Weismann, Mr. Butler, following other authors, refers Tilia to 

 the genus Afimas, Populi to Laothoe, and Ocellatus to Smerin- 

 thus. It is to be hoped that when our knowledge of the 

 developmental history of larvae is more complete in all groups, 

 a reconciliation between the results of the biological investi- 

 gator and the pure systematist will be brought about, so that 

 a genus may not, as at present, have such very different values 

 when regarded from these two points of view. R.M.] 



