FOLSOM: “MOUTH-PARTS OF ANURIDA MARITIMA. 149 
the ocular segment, every somite is represented by a pair of append- 
ages. I find no evidence whatever for more than seven primitive 
cephalic segments, and believe that my observations have assisted 
to settle the long-disputed question of the segmentation of the 
head. : 
Since the time of Fabricius, the mouth-parts of insects have been of 
primary importance for the systematist. While insisting that a logical 
classification must recognize all anatomical structures, it must be ad- 
mitted that the mouth-parts are of fundamental systematic value on 
account of the range of their differentiation. 
Without discussing at length the phylogeny of insects, I may briefly 
give the bearing of these studies upon the subject, remarking that my 
conclusions are in entire accord with approved views upon the origin 
of insects. 
The Collembola are strikingly like Campodea and Japyx in structure, 
their peculiar entognathous characteristic separating these three groups 
from all other insects. The Collembola as a group are somewhat more 
specialized than the Thysanura in general structure. The Smynthuride, 
with their globular bodies, vertical heads, and well-developed furcule 
and ventral tubes, represent one extreme of differentiation — compara- 
tively high. The Aphoruride, including Anurida, with vermiform 
bodies, subequal segments, horizontal heads, no furcula, etc., are much 
more generalized, and probably degenerate forms. Anurida, for ex- 
ample, has both pairs of maxillary palpi, as well as rudimentary ab- 
dominal appendages and the fundaments of a furcula in the embryo, 
but in the embryo only. Therefore the ancestral Collembolan was 
probably intermediate between Smynthuride and Aphoruride, and is 
most nearly represented by members of the family Poduride. The 
resemblance in the mouth-parts leads us to suppose that the primitive 
Collembolan descended from the stem form of Campodea and not far 
below Campodea itself. 
The affinities of Campodea, which is slightly more primitive than 
Japyx, are in two.directions: towards Machilis and Lepisma on the one 
hand, and towards Scolopendrella on the other. In the first two genera 
the mouth-parts are clearly derivable from the Campodean type, and 
link Campodea with Orthoptera. In regard to Scolopendrella, it was 
long uncertain whether it should be placed among Thysanura or 
Myriopoda, on account of its strong affinities for both. Most authors 
have followed Grassi and placed it in the latter group, always admitting 
its insectean features. In the month-parts, Scolopendrella approaches 
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