228 Studies in the Theory of Descent. 



view, since the absence of ring-spots on the three 

 front segments in the young caterpillar (one 

 instance), or their less perfect formation on these 

 segments (second instance), indicates a forward 

 transference of the spots. 



If the foregoing view be accepted, there follows 

 from it a fundamental difference between the 

 development of the genera Chczrocampa and 

 Deilephila. In the former the formation of the 

 eye-spots proceeds from a subdorsal line, but they 

 first appear on two of the front segments, and are 

 then transferred to the posterior segments. In 

 Deilephila, on the other hand, a single ring-spot 

 is formed on the penultimate segment bearing the 

 caudal horn, and this is repeated on the anterior 

 segments by secondary transference. With respect 

 to the origination of the ring-spot also, there is a 

 distinction between thiu genus and Chcerocampa, 

 inasmuch as t'he first step towards the eye- 

 formation in the latter consists in the separation of 

 a curved portion of the subdorsal line, whilst in 

 Deilephila the nuclear spot first seems to originate 

 and the separation of the mirror-spot from the 

 subdorsal line appears to occur secondarily. It is 

 difficult here to draw further conclusions, since the 

 first appearance of the primary ring-spot has not 

 yet been observed, and no more certain inference 

 respecting the history of the formation of the 

 primary ring-spots can be drawn from the manner 

 in which the secondary ring-spots are formed. 



