178 
ORIGIN OF LIFE IN AMERICA 
are situated in the southern States of North America. It is 
suggested by Dr. Ortmann that the south-eastern centre of 
the early forms of Cambarus originated from the more ancient 
south-western one by a process of migration across the present 
continent. May not these early forms have travelled eastward 
from Mexico towards Cuba and Florida when the latter were 
connected directly by land with Central America ? A species 
of Cambarus still lives in the rivers of Cuba. 
Instead of mollusks or crayfish we may take almost any 
group of North American invertebrates and readily discover 
among them certain ancient forms, which are either confined 
to small areas in the south-eastern States or have evidently 
spread northward from a south-eastern centre. 
Scorpions, for instance, are universally acknowledged to be 
a very ancient group. The genus Centrums has its head¬ 
quarters in the West Indies and Central America. Now 
four species of Centrums are known from Florida, viz., C. 
gracilis, C. carolinianus, C. margaritatus and C. hentzi, the 
latter being peculiar to Florida. The allied genus Tityus, 
which is rather more southern in distribution than Centrums, 
has one endemic species in Florida, viz., T. floridanus.* 
Altogether the southern part of Florida shows marked affini¬ 
ties with the West Indies. There are also some species in 
Florida such as Cupiennius sallei, Keys, not yet recorded from 
the Antilles, which are known from Central America. Quite a 
similar southern relationship has been noticed among many of 
the Floridian Orthoptera f and the Coleoptera. J One of 
the most noteworthy genera of beetles recorded from Florida 
is Rhopalomesites. It has spread northward as far as Dela¬ 
ware, and reappears across the Atlantic in western and 
southern Europe. 
As regards the dragon-flies and their allies (Neuroptera), a 
few species are common to the West Indies and the northern 
continent. Some of these may have flown, or have been con¬ 
veyed by a storm, from one region to the other. Such a method 
of colonisation, however, cannot have been used by Enallagma, 
* Banks, Nathan, “ Arachnida of Florida,” p. 142. 
j Rehn, J. A., and M. Hebard, “ Orthoptera of Florida.” 
J Schwarz, E. A., “ Coleoptera of Florida.” 
