EVOLUTION IN NATURAL SCIENCE 11 



pare the formation of the wings with that of the 

 Blattidse, or cockroaches, both fossil and still 

 existent, we shall probably find that the termites 

 in some prehistoric palaeozoic age were evolved 

 from one and the same stock as the ancestors 

 of our present black-beetles. 



I might give many such instances, but it is time 

 for me to pass on to my photographs. They 

 represent the inquilines, living among ants and 

 termites, and we shall observe a number of in- 

 teresting phenomena, which are biologically ex- 

 plicable only from the point of view of evolution. 



[At this point some photographic lantern slides 

 were displayed. 1 ] 



To illustrate the statement regarding direct proofs the 

 lecturer displayed photographs of the varieties of the 

 Dinarda, a kind of beetle which lives with the ants, and is 

 still producing new forms. He also showed species of the 

 genus Doryloxenus, which in comparatively recent times in 

 the East Indies have ceased to live with the ants and have 

 become guests of the Termites, thus being changed into 

 new systematic varieties. The same change was shown to 

 have taken place in some African species of the genus 

 Pygostenus. 



Subsequent photographs illustrated the indirect means of 

 justifying the theory that new species, genera, and families 

 are formed by variation due to accommodation. These pho- 

 tographs also were chosen from the department of science 

 which the lecturer has made especially his own. Most of 

 them represented brachyoptera, beetles with very short 



1 For further details and illustrations, see Modern Biology, chap. x. 

 pp. 323-431, and also ' Instances of Eecent Formation of Species among the 

 Inquilines of Ants and Termites,' Biol. Zentralblatt, 1906, Nos. 17 and 18. 



