A feviston of the Genera of the Avanee. AS 
seen this variety in the field, its normal habitat lying con - 
siderably north of this locality. It would, however, be 
dangerous to base any conclusions upon an isolated case of 
this kind. 
From the foregoing facts it seems probable that, in the case 
of those species which are amenable to the influences of 
climate, the stimulus necessary to induce seasonal change 
would consist in a combination of either moisture and heat 
or dryness and cold, and not in either of these factors exclu- 
sively. | 
Two years ago I made a few experiments in applying moist 
heat to the pupz of several species of Teracolus. Unfortu- 
nately all my notes on the subject have been lost, but, so far 
as I ean recollect, the results were almost entirely negative, 
which I then attributed to insufficient heat. The resulting 
Specimens were, however, sent to the Oxford University 
Museum with full data, and such of the insects as are worth 
preserving from the present experiments are being sent to the 
same institution. 
Salisbury, Mashonaland, 
August 1901. 
LI.—A Revision of the Genera of the ARANEZ or Spiders 
with reference to their Type Species. By F. O. PicKArD 
CAMBRIDGE, B.A. 
In the ‘ Annals & Magazine of Natural History ’ for January 
1901 I have discussed the question of the determination of 
type species for various genera and have briefly detailed the 
main features of that method of selecting type species amongst 
heterotypical genera which is usually known as “elimination ” 
or ‘‘ exhaustion.” 
My remarks have called forth prompt criticism from 
Dr. Dahl, in a paper published in the ‘ Archiv fiir Natur- 
geschichte,’ Jahrg. 1901, under the title “ Die internationalen 
Nomenclaturregeln und ihre Anwendung auf die altesten 
Spinnengattungen.” 
In this paper the author questions not only the application 
of the principles Jaid down in relation to the special cases 
dealt with, and the value of the methods themselves, but 
he -even goes so far as to doubt whether there is any 
necessity for the selection of a type species at all. 
Now, before we enter the field of discussion as to the 
methods and rules whereby a type species is to be recognized, 
29* 
