MICROSCOPY. 761 
seem as though the inhabitants had provided for a retreat in case 
of the capture of either half of the town. The southern half is 
far better defended, naturally, by ravines and steep inclines, and 
artificially by its double walls, so that this may well have been the 
first home of the people who, afterwards, extended the limits of 
their walled town northwards. The weakest portion of the fortress 
- is on its northeastern side where the artificial embankments are 
unusually high and steep, and where the main gateway opens out 
upon a broad level field on which is erected the mysterious enclos- 
ure whose outlines are given by Locke. The mound at the farther 
end of this enclosure I should say might well have served as a 
watch-tower either for the besieged or the besiegers,—its parallel 
walls affording means of escape and of defence. It is not clear to 
me but that the forest may have been allowed to stand both within 
and without the fort, even during its occupation, the trees being 
indeed an advantage both as protection against sun and wind, and 
as affording great help in actual combat.—CLEVELAND ABBE. 
[Being unable to reproduce Mr. Abbe’s drawings we have omitted his letters of 
reference.—ED 
MICROSCOPY. 
DISTRIBUTION oF THE Ru1zorops.—At a meeting of the Academy 
of Natural Sciences of Philadelphia Prof. Leidy remarked that 
while it was exceptional to find the same species of the higher 
sub-kingdoms in-the different parts of the world, it appeared to 
be the rule that most species of Protozoa were found everywhere 
under the same conditions. A large number of our fresh-water 
forms he had recognized as the same as those described by Euro- 
pean authors. A less number of species are probably peculiar 
to every region. Among our fresh-water izopods he had 
served not only the genera Ameba, Arcella, Diffugia, Euglypha, 
Trinema, Lagynis, Actinophrys, etc., but also most of the species 
of these as indicated by European naturalists. It is an interesting 
question whether our fresh-water Protozoa have reached us from 
‘the same sources as those of Europe and other remote countries. 
If derived from the same sources they were probably infused in 
the waters of the different continents at an early age when the 
latter were not separated by ocean barriers. If thus early infused 
we have a remarkable instance of a multitude of specific forms 
retaining their identity through a long period of time. Sucha 
view might appear to oppose the doctrine of evolution, but not 
