194 THE CANADIAN ENTOMOLOGIST. 



ON GENERA. 



BY DR. H. HAGEN, CAMBRIDGE, MASS. 



(Read before the Entomological Club of the A. A. A. S.,at Buffalo, N. Y.) 



There will hardly be a naturalist who has not spent considerable time 

 to study the questions — What is a genus, and what are generic characters? 

 Indeed, work is nearly impossible without having taken a position with 

 regard to these questions. A full record of the literature, even the most 

 condensed one, would be here -out of place, but I have been induced by 

 a recent and most surprising discovery bearing upon this question to make 

 this communication. I have been speaking here only about natural 

 genera. The consideration of the genus as an artificial division differs 

 fundamentally, and to avoid mistake we should not call artificial divisions 

 by this name. The characters of artificial genera depend solely upon the 

 taste of the worker and the convenience of separating into groups animals and 

 plants. All species are considered to belong to the same natural genus which 

 agree in structural characters, external and internal, or anatomical ones 

 in the different stages, in transformation, in the manner of living. These 

 definitions of a genus are accepted as well by naturalists who are strong 

 Darwinians as those who oppose the development theory. In a prize 

 essay of the Jena University, D. P. Mayer, a pupil of Prof. Haeckel, in a 

 paper on the " Ontogeny and Phylogeny of Insects," enlarges this 

 definition in so far as he asks for a conformity in the embryological char- 

 acters. I believe no one will object that this definition is a good and 

 exhaustive one ; but if we attempt to use it in a special case we become 

 bewildered by the astonishing amount of characters unknown to us, and 

 the impossibility to make them out for our work. At present we know 

 hardly well enough the external characters of the imago. Of -other 

 characters our knowledge is merely fragmentary and often a tabula rasa. 

 We may say that a century of hard work will not fill these gaps in our 

 knowledge. It is obvious that we cannot wait till this enormous amount 

 of work is done. And it is certain that naturalists will not and can not 

 stop creating new genera. 



Genera created with such a limited amount of knowledge will depend 

 upon the experience and taste of the worker. Many of such genera will 

 have to be modified or dropped by a farther advancing knowledge. 



