14 
WORK IN EUROPE 
earlier geological period; (3) Tromoptera , for the prevailingly aerial 
Diptera (. Nemestrinidae , Cyrtidae , Bombyliidae , Therevidae , Scenopi- 
nidae ); and (4) Eneryopoda for the pedestrian Diptera ( Asilidae , 
Dolichopodidae , Empidae , Lonchopteridae , Phoridae ). Objections 
have been raised against the juxtaposition of the Asilidae and the 
Dolichopodidae , etc., in the same superfamily. I believe that this 
juxtaposition is sufficiently justified by the structure of the head, of 
the antennae, and of the genital organs in this superfamily as con¬ 
ceived by me, and that the connection between the Asilidae and the 
rest of the families comprised in it is found in the Mydaid-like and 
ancestral section Apiocerina , the different forms of which occur in 
Australia, Chili, and some parts of North America, which are coun¬ 
tries abounding in ancestral forms. 
I feel convinced that the new distribution of the Orthorrhaplia Bracliycera 
which I have proposed is better than the previous one. But at the same time I 
am far from expecting, or even desiring, that it should be immediately accepted 
in handbooks of dipterology, or introduced into collections of Diptera. My 
feeling about it is distinctly expressed in the last passage of my Preliminary 
Notice, etc. ( Berl . Ent. Zeit., 1896, p. 373), which says : “My paper is a ballon 
d’essai, which I launch, attentive to the course it will follow ! ” Much remains 
to he done in anatomical and biological research before the final introduction of 
my new arrangement into dipterological practice can take place; and Dr. D. 
Sharp, in his Insects (London, 1899, p. 456-457), has set a good example in not 
adopting this arrangement, but in giving a short account of it, and calling the 
attention of advanced students to it. 
The views concerning Zoological Classification and the Nomen¬ 
clature connected with it which I have gradually developed during 
my studies may be summed up as follows: I understand the office 
of both to be merely mnemonic : they represent a scheme for the 
arrangement of animal forms tending to make the affinities exist¬ 
ing between them tangible and easier to remember. I expressed 
this opinion for the first time in the Berl. Ent. Zeit., 1895, p. 160, 
144 (1895) in the following terms : “ The true end of classification 
is an easier survey of affinities, a temporary aid to memory. In 
space and time all divisions become convergent and finally con¬ 
fluent.” Classification is not necessarily permanent. If zoologists 
had existed in different geological epochs they would have intro¬ 
duced different arrangements, to answer the requirements of their 
