MYGALOMORPILE. | 3 
habit tends to similarity in structure without there being, necessarily, any near 
elationship between the forms. : 
When we enter upon the question of the distribution of particular groups and genera 
over wide areas and continents separated by broad seas, and whether certain definite 
forms are more or less confined to certain well-marked regions, we have first of all to 
bear in mind that the Mygalomorphe do not lend themselves so greatly to the usual 
agents of distribution as do the Arachnomorphe. ‘The former usually live under 
ground and upon the ground, and the egg-cocoon is not so likely to be carried in cargoes 
of vegetables and plants, for instance, from one hemisphere to another. Neither 
are their young so likely to be conveyed by the winds high up in the air from island 
to island and continent to continent, clinging to the masts and rigging of ships. 
Indeed, I have never heard that the young of any of the Mygalomorphe migrate in 
this manner, a common occurrence amongst the Arachnomorphe. As an instance 
of the distributing agency of steamers and ships in the case of the latter we may note 
the occurrence of the huge Heteropoda venatoria (regia, Fabr.) in almost every seaport 
of the tropical world, and one of the most familiar house-spiders to dwellers in the 
‘tropics. ‘They thrive amazingly in the warm holds and engine-rooms of the steamers, 
and have thus been transferred from port to port all over the world from their original 
headquarters. possibly somewhere in the oriental equatorial regions. 
With the Mygalomorphe, however, artificial or semi-natural distribution is far less 
likely to occur, and therefore we are more justified in concluding @ priori that the 
forms occurring, for instance, in Hindostan, Burmah, and Borneo will be strikingly 
different from those to be met with in Central America and Brazil, than we should be 
in the case of the Arachnomorphe. 
And as a matter of fact such @ priort judgment is, to a very great extent, borne out 
by actual comparison of the fauna from these widely separate regions; for compared 
with that of the western hemisphere we find the fauna of the Oriental region present 
striking differences. 
It is of course too soon to speak with certainty on the matter, but with regard to 
the family Theraphoside, at all events, we may affirm that, as a rule, the Neotropical 
members differ in certain very definite characters from those of both the Ethiopian and 
Oriental regions. The genera are entirely distinct, and although some of them are 
supposed to be common to Central America and to the European Mediterranean region 
(e. g. Chetopelma and Cratorrhagus), | am not in a position at present to confirm this 
supposition. 
The Theraphoside from the equatorial regions of the east possess in the stridulating- 
organs of both male and female a character which separates them at once from those of 
the Neotropical region. Curiously enough, however, in the case of the family Dipluride 
the position is almost exactly reversed, for in the Neotropical genera Zrechona, 
Melodeus, and Harmonicon the stridulating-apparatus is present, while in members 
Bt 2 
