ox THE ORIGIN OF GEXERA. 



89 



Here is a case where all the species but two change their 

 generic characters ; one changes them or not, according to cir- 

 cumstances, and one does not change them at all. What are the 

 probabilities respecting the change in the first set of species ? 



As we know from the experiments of Hogg, Dum^ril, and 

 others that metamorphosis is greatly hastened or delayed by the 

 conditions of temperature and light, what would not be the effect 

 on such a protean si^ecies of a change of topographical situation, 

 such as the elevation or depression of the land ? And I have no 

 hesitation in saying that if the peculiarities of series of individuals 

 of A. tigrinum and A. mavortium, in the respects above enumer- 

 ated, were permanent, they would characterize those series as spe- 

 cies, as completely as any that zoologists are accustomed to recog- 

 nize. For the evidences on this head, see the discussions of those 

 species in my monograph. 



The exj)eriments of Hogg, above alluded to, are as follows, as 

 given by him la the "Annals and Magazine of Natural History." 



He placed a number of impregnated ova of frogs in vessels 

 arranged at regular distances from the light, in a cave. The les- 

 sening degrees of light were of co^^rse accompanied by a corre- 

 sponding but much less rapid decline in temperature. The result- 

 ing effects on the metamorphosis may be tabulated as follows : 



3. The reproduction of some species of insects before they 

 complete their metamorphosis is a well-known fact, and it is par- 

 ticularly to the point that, in many of them, some individuals do 

 attain to their full development, while the many do not. "West- 

 wood says,* "Two British species of this family (the Keduviidje), 

 Prostemma gnttuJa and Coramis suhapterus, are interesting on 

 account of their being generally found in an undeveloped state, 

 the latter being either entirely apterous or with the fore-wings 

 rudimental, although occasionally met with having the fore-wings 



* Uhler informs me that Amyot's asserted color characters are not reliable. 



