On EUROPEAN SPIDERS. 173 
We arrange the European Thomisoide under the following genera: 
§ Mamillæ ut et ungues in apice tarsorum adsunt. 
* Pedes 4 posteriores reliquis non vel parum graciliores, sæpissime iis non vel 
parum breviores. Tarsi in apice sub unguibus fasciculis duobus pilorum plus 
minus dilatatorum instructi. . . . . . . . . . . J. PHILODROMINAS. 
A. Utraque oculorum series ex oculis 4 composita. 
a. Oeuli medii antiei vix vel non longius a margine clypei quam a me- 
diis postieis remoti. Maxille plerumque rectæ et parallele.  (Fasciculi 
unguieulares spississimi, ex pilis longis, tenuibus, in ipso apice tan- 
tum paullo dilatatis constantes). 
1. Series oculorum antica paullo recurva, postica, desuper visa, paullo 
procurva. (Oculi intermedii in trapezium antice angustius dispositi). 
Genua pedum altius elevata. . . . . . . . . 1. Micrommata. 
with the two great main divisions of the organie world, the animal and vegetable 
kingdoms: all these various kinds of systematie unities have been formed on 
the strength of a certain, greater or less, number of common features, which the 
natural productions united under them seem to us to possess, and although we see 
now a greater, now a less saltus between the most nearly related coordinate groups, 
yet the differences in this respect do not affect the propriety of considering them 
as independent genera, families, orders, etc., provided only their typical forms 
show the amount of peculiarities, which one assumes to be necessary for a group 
to be acknowledged as possessing the signifieancy of a genus, family, etc., and 
provided some sure, even if insignificant, feature can be pointed out as determining 
in doubtful cases the limit of the group. The groups, which, like e. g. the genera 
Dinopis and Hyptiotes among Spiders, or like this and most other orders within 
the class of Arachnoidea, do not exhibit transitions to any other group, are 
comparatively few; and how vast differences in this respect are visible between e. g. 
the different orders of the class Crustacea on the one and of the Arachnoidea on the 
other hand! And yet surely no one will deny, that for inst. Copepoda and Branchio- 
poda are as natural and rational orders as Araneæ and Opiliones, although the 
boundary between the former is not so sharply defined, but that the same genus 
(e. g. Argulus) is referred by some authors to the Copepoda and by others to the 
Branchiopoda. Precisely similar to the relation between these two orders, is that 
between many genera, and among them that between 7homisus, Moneses and 
Philodromus: transitions there are, it is true, but the groups are on the whole and in 
their tupical forms sufficiently different, to deserve their separate denominations and 
the rank in the system, which it has hitherto been customary to give them. — The 
more new forms (especially fossile ones) are discovered, the more the intervals between 
a number of genera and of higher groups, which had previously been considered as 
widely separated, are filled up. If we were fully acquainted with the entire animal 
and vegetable world, both the now living and the extinct, all such gaps would as- 
suredly be filled up, and the truth of the old adage: natura non facit saltus, would 
stand out in all its grandeur. 
