284 
HALF HOURS WITH INSECTS. [Packard. 
affinity, in order that these two series may be virtually 
brought together; while the successive forms in the several 
families shall afford us some conception of the larger cate¬ 
gories these minor groups foreshadow. Such a group Pro¬ 
fessor Agassiz * has pointed out in the class of Selachians, 
which combine the characters of all the other classes of 
fishes existing during the same period, and also, by their 
being the earliest in time, afford what he calls prophetic types 
Fig. 220, Fig. 221. 
of all the coming classes of vertebrates. The former case 
affords what he calls synthetic types” 
In endeavoring to show that a similar synthesis as marked 
as in the fishes or reptiles, or other groups of animals, occurs 
in the different neuropterous. families of insects, the case of 
the Lepisma (Fig. 220, L. quadriseriata) or bristle tail, may 
be cited, which is closely allied to the Campodea (Fig. 221), 
* Essay on Classification. 
28 
