No. I.] CONTRIBUTION TO INSECT EMBRYOLOGY. 1 05 



The development of the brain of Blatta gernianica and 

 Melanopliis fcmiir-riibrum agrees in all essential respects with 

 the development of the Xiphidiiim brain. Certain Hemiptera, 

 e.g. Ranatra fusca, conform very closely to the type of brain 

 structure seen in these Orthoptera. I may mention in this 

 connection that the brain of Anurida viaritiiua shows the 

 typical division into proto-, deuto- and tritocerebral segments 

 with great distinctness. The last segment especially is re- 

 markably distinct. 



Until very recently the detailed study of the embryonic 

 Hexapod brain has been limited to the Coleoptera and the 

 results obtained have been naturally enough extended to 

 include not only other insects but other Arthropods as well. 

 The Coleoptera, however, are far from being primitive forms 

 and the role which they play in contemporary embryological 

 literature is largely attributable to the unusual technical ad- 

 vantages presented by their eggs. As far as development is 

 concerned, the simpler brain of the Orthoptera and Ametabola 

 in general offers many points of resemblance to the Crustacea 

 and Myriopoda,^ whereas the brain of the Metabola, like so 

 many other points in their organization bears witness to a 

 considerable amount of modification. It is therefore more 

 consistent with our general views of phylogeny to reduce the 

 Coleopteran brain to the Orthopteran type than to proceed 

 vice vcjsd. 



We owe the most important contributions to the subject of 

 Orthopteran brain development to Viallanes. After a decade 

 of study devoted to the histological structure of the adult 

 Arthropod brain he has selected Mantis as a subject for 

 embryological investigation. His previous careful study of 

 the adult brain of other Orthoptera (CEdipoda coemlescens 

 and Caloptenus italicus, '87'') has enabled him to avoid the con- 

 fusion with which the inexperienced investigator is overwhelmed 

 when attempting to follow the rapidly increasing complication 

 of neural structures. With his usual skill and patience he has 

 traced the development not only of the main structural features 

 but of many details, so that we have a well-established point 



1 See the papers of St. Remy ('90) and Viallanes ('87^ '87^'). 



