1008 7 General Notes. [ December, 
cases they seem actually to require a certain amount of desic- 
cation before they will hatch. Yet the fact remains that dif 
ferent species act differently in this respect. In short, nothing is 
more patent to the observing naturalist than that species, and even 
individuals of the same species, or the progeny of one and the 
same individual act very differently under like external conditions 
of existence ; or in other words, that temperature, moisture, food, 
etc., influence them differently. Hence—as has been shown by 
Semper to be the case with other animals, so it is with insects— 
changes in the external conditions of existence will not affect the 
fauna as a whole equally, but will act on individuals. We can 
understand how this great latitude in susceptibility to like condi- 
tions may and does in the case of exceptional seasons prove 
beneficial to the species by preserving the exceptional individuals 
that display the power to resist the unusual change, but we shall 
find ourselves baffled when we come to seek a demonstrable ex- 
planation of the cause or causes of such retardation, while the 
principles of evolution afford us the only hypothetical one at all 
satisfactory. 
In the innate property of organism to vary and in the complex 
phenomena of heredity, we get a glimpse at the cause—a partial 
explanation—of the facts of retarded development, for the excep- 
tional tendency in the present may be looked upon as a manifes- 
tation, through atavism, of traits which in the past had been 
more commonly possessed and more essential to the species. 
This hypothesis is strengthened by the fact that the period of 
two, three or more years occupied in full development by excep- 
tional individuals of a species which normally goes through its 
transformations within one year, is at the present day the normal 
period in other species belonging to the same natural order. 
PREPARATION OF Diprera.—Prof. Joseph Mik, of Vienna,has, 1n 
the Verhandlungen der K. K. zcologisch-botanischen gesellschaft td 
Wien for 1880 (reprinted in Katter’s Entomologische Nachrichten, 
1881, pp. 189-206) an elaborate article on the Preparation of Dip- 
tera for cabinets, and we recommend a perusal of it to our dipter- 
ists, whether beginners or advanced students. It is evident from 
the paper that the proper preparation of Diptera for a cabinet, so 
as to render the specimens fit for ‘scientific determination and 
study, requires more care and delicate manipulation than in any 
other order of insects. It is an art which can only be acquired 
by long practice, and we are glad that Professor Mik gives us the 
nefit of his life-long experience. 2 
Tue PERMANENT SuBsecTION oF ENTOMOLOGY AT THE siete 2 
A. A.S.1—Mr. Lintner’s paper “on 2 Tre 
