THE CANADIAN ENTOMOLOGIST. 195 



The most important question (what are generic characters ?) is still 

 unanswered. 



The large literature and the difference of opinion emitted by pro 

 minent authorities seem to prove that a sufficient affirmative answer is 

 impossible till our knowledge is further advanced. But here, as in other 

 abstract questions, we can proceed in a negative manner by exclusion. 



Genera consist of a number of related species. If we knew the char- 

 acter of the species, the specific character, we can by exclusion come 

 nearer to the character of the genus. Species differ by structural 

 character, and as the species form the lowest degree of the classification, 

 we can be sure that species must differ at least by minutest points of 

 structure. 



I think there is no objection of consequence possible. I know very 

 well that differences in minuter points of structure have been considered 

 as generic characters. But naturalists beginning with the construction 

 and definition of the higher degrees of class, order, family, &c, used up 

 all characters at hand, till, coming to genera, nothing was left but minute 

 differences of structure ; the simple consequence of having used specific 

 characters for generic ones was that nearly every species was considered 

 to be a genus. 



I said before that species must differ at least by minuter points of 

 structure. The discovery which I mentioned before proves that structural 

 characters of species are more important, and can by a different manner of 

 living be changed in such a way as to represent forms which were formerly 

 believed to belong to different genera. Branchipus and Artemia, belong- 

 ing to the Phyllopod Crustacea, are represented by several species here 

 and in Europe. The two genera are nearly related one to the other, and 

 differ principally in the following points: Artemiahas eight post-abdominal 

 segments, the last one very long. Branchipus has nine post-abdominal 

 segments, the last two of equal size. Artemia has three articulated 

 claspers in the male ; Branchipus two articulated claspers. Artemia is 

 often propagated by Parthenogenesis, Branchipus never. 



Nobody will deny that those characters of structure go very far beyond 

 minuter points of structure, and are marked well enough to justify the 

 separation sixty years ago by Dr. Leach. Now, it is proved that not only 

 the species of Artemia known up to to-day from Europe, Asia and Africa? 

 but even some species of Branchipus belong to one and the same genus and 

 species. In the American fauna five species of Artemia and three of 

 Branchipus are described  of course they will have to be studied again 



