The Origin of the Markings of Caterpillars. 327 



account, be assumed without further inquiry, that 

 they are called into existence by the same causes ; 

 they must rather be investigated separately, from 

 their origin. 



Eye-spots are possessed by the genera Chczro- 

 campa and Pterogon ; ring-spots by the genus 

 Deilephila. In accordance with the data furnished 

 by the above-given developmental histories, the 

 origination of these markings in the two genera 

 may be thus represented : 



In the genera named, eye-spots and ring-spots 

 are formed by the transformation of single portions 

 of the subdorsal line. 



In Chcerocampa the primary ocelli originate on 

 the fourth and fifth segments by the detachment 

 of a curved portion of the subdorsal, this fragment 

 becoming the " mirror," and acquiring a dark 

 encircling zone ("ground-area"). The nucleus 

 (pupil) is added subsequently. 



In Deilephila we learn from the development of 

 D. Hippophaes, that the primary annulus arises on 

 the segment bearing the caudal horn (the eleventh) 

 by the deposition of a red spot on the white 

 subdorsal line, which is somewhat enlarged in this 

 region. The formation of a dark " ground-area " 

 subsequently occurs, and with this, at first the par- 

 tial, and then the complete, detachment of the 

 mirror-spot from the subdorsal line takes place. 



In both genera the spots arise at first locally on 

 one or two segments, from which they are trans- 



