180 BRITISH CICADA. 



was mncli the same as we find it in recent families, 

 and so much so that the ancient impressions of 

 Homoptera will tell us as much as to their generic 

 alliances, as recent wings now do of our present genera. 



On the other hand, Mr. S. Scudder shows that dete- 

 rioration or degradation obtained in geological times ; 

 and that atrophy of the two fore-legs in certain 

 butterflies, such as the fossil representatives of the 

 Nymphilidae, was commencing at a period when the 

 Florissant beds were in i^rocess of deposition. 



I do not find amongst the numerous finely drawn 

 figures of fossil Cicadae of the United States of 

 America any atrophy of the lower wings, which we so 

 commonly find in living Tettigidse, and which has 

 become almost the rule in the modern Delphacidae. 



Notwithstanding any probability there may be that 

 the existing orders of insects in distant times were 

 evolved from primitive types ; it must be confessed 

 that the proof of such has not gained much, if 

 any, strength through our more advanced knowledge 

 of fossil insect forms. Geology has been called the 

 archaeologist of biology ; but it has been many times 

 observed that when new forms of ancient life appear 

 in the rocks, they mostly do so fully specialized. 

 There seems, indeed, to be no process at work 

 which could in any way be irreverently considered as 

 tentative. Long periods of time, doubtless, are neces- 

 sary to form even permanent races. It is, therefore, 

 quite useless to speculate on what might be required 

 to introduce a new species. 



According to Mr. Wm. Carruthers, the lapse of time 

 from the pre-giacial age (roughly taken as 250,000 

 years) is too small to show any appreciable change in 

 any known species of plants, that is so far as our 

 materials admit of any comparison between them. 



Dr. Schweinfurth has shown by careful comparisons 

 that the existing Nile plants and fruits do not differ 

 from those unrolled from mummy-clothes 3000 years 

 old. Such plants, he says, show no marked variation. 



