THE CANADIAN ENTOMOLOGIST 143 



To these are added a chapter on British species and a final one 

 on "Collecting, Rearing and Biological Methods." 



The book teems with suggestive ideas, particularly regard- 

 ing the phylogeny of various characteristic structures, such as the' 

 anal appendages, the pterostigma, the nodus and other venational 

 features, the rectal gills of the Anisoptera, the caudal gills of the 

 Zygoptera and the types of colour pattern. The wings of the' 

 Zygoptera are regarded as having been originally anisopterous, 

 as were those of the fossil order Protodonata, their general reduc- 

 tion, especially in the anal area of the hind wings having been cor- 

 related with their use as mere "sculling organs" with no power of 

 soaring or "planing." 



In the scheme of classification adopted, the chief deviation 

 from the systems usually followed is the separation of the family 

 Lestida?, with three subfamilies Epiophlebiinae, Lestinae and 

 Synlestinae. This change is based upon both imaginal (vena- 

 tional) and larval characters and appears to be well founded. 

 • Diagnostic characters are given for all the groups as far as the 

 tribes. 



The subject of Zoogeographical Distribution is considered 

 from a somewhat novel viewpoint. The fauna of each geographi- 

 cal region is divided into three main groups, palseogenic, entogenic 

 and ectogenic. The palaeogenic fauna consists of isolated rem- 

 nants of a past age, formerly more widely distributed than at 

 present; the entogenic fauna of those groups which are most 

 characteristic of the region in question, where they may form 

 definite "zoocentres;" while the ectogenic fauna consists of such 

 groups as have invaded the region from some neighbouring region 

 in which they are entogenic. The same genus may be entogenic 

 in more than one region. Separate tables are given of both ecto- 

 genic and entogenic genera, and their distribution in the various 

 regions. 



The fossil record, described in the next chapter, also contains 

 many interesting suggestions, such as the probability that the 

 larvae of the Protodonata dwelt in damp earth rather than water, 

 no larval forms having been preserved among the abundance of 

 imaginal remains in the Commentry deposits, and the larval 

 tracheal svstem of recent forms being a modification of an originally 



