FACTS FOR THE THEORY OF EVOLUTION. 



105 



irg example of the unity of type of the jointed appendages of 

 insects, and articulates generally. 



Another point of interest in these degraded insects is, that 

 the process of degradation begins either late in the life of the 

 embryo or during the changes from the larval to the adult, or 

 winged state ; An instance of the latter may be observed in the 

 wingless female of the canker worm, so different from the winged 

 male; this difference is created after the larval stage, for the 



caterpillars of 



both sexes are 



the same, so far 



as we know. So 



with numerous 



other examples 



am on g the 



moths. In the 



louse, the em- 

 bryo, late in its 



life, . resembles 



the embryos of 



other insects, 



even Corixa, a 



member of a not 12G - Antenna? of 

 Goniodes. 



125. The Turkey Louse. 



remotely allied family. But just before hatch- 

 ing the insect assumes its degraded louse physiognomy. The 

 developmeutist would say that this process of degradation 

 points to causes acting upon the insect just before or immedi- 

 ately after birth, inducing the retrogression and retardation of' 

 development, and would consider it as an argument for the 

 evolution of specific forms by causes acting on the animal while 

 battling with its fellows in the struggle for existence, and per- 

 haps consider that the metamorphoses of the animal within the 

 egg are due to a reflex action of the modes of life of the ances- 

 tors of the animal on the embryos of" its descendants. 



