KESULTS OF PAL^ONTOLOGICAL RESEARCH 41 



enough for specialization and particularly also the 

 formation of the jaws, which are already differentiated 

 for masticating, stinging, sucking, etc. 



In many cases the specialization was associated 

 with regression, with reduction of the number of wings 

 and segments. 



As an external impulse to variation Handlirsch 

 cites the Permian glacial epoch which, particularly, as 

 a result of the general cooling, may have caused the 

 transition of the larval forms into perfectly metamor- 

 phosed ones as ' being generally better fitted for cold 

 seasons/ For the late appearance (and origin) of the 

 Wasps, Ants, Bees, and Gall-flies, Handlirsch considers 

 that in the appearance and rich development of the 

 flowering plants, a sufficient reason is to be found. 



Wasmann l expresses his opinion regarding the 

 history of the origin of insects, as Handlirsch presents 

 it, as follows : ' In the hypothetical history of insect 

 origin certainly a manifold differentiation and specializa- 

 tion of the insect type has taken place, which was 

 connected, partly with an increased development of 

 certain characters, and partly with a reduction in others. 

 Of an enhancing of the entire organic type naught 

 can be said. ... A wingless worker ant can by no 

 means be considered as " a more perfect insect " than 

 a six-winged Pabeodictyopteron was. The primary 

 insects and those of their present descendants which, 

 like the Ephemeridse, have retained many of the 



1 Die progressive Artbildung und die Dinarda-Formen in Natur und 

 Offenb., 1909, no, 6, p. 333. 



