32 THE AMERICAN NATURALIST. [Vor. XXXVI. 
development of the embryo it moves forward, and in adult 
insects it constitutes the dividing line between the head and 
the thorax, forming the neck. Its appendages, the second 
maxillae or labium, however, have moved forward so that they 
are either loosely attached to the ventral wall of the head 
(Plecoptera, Orthoptera, e/ al.) or, in the more specialized 
orders, they contribute to the formation of the fixed parts 
of the head. 
While the appendages of this segment have been retained 
and play an important róle as a part of the mouth organs, the 
segment itself is greatly reduced, being represented by small 
and more or less detached sclerites, the cervical sclerites. 
Straus-Durckheim (28) suggested that the cervical sclerites 
represent the remains of two segments situated originally 
between the head and prothorax. Newport (39) regarded 
i them as detached portions of the pro- 
thorax; and Huxley (78) wrote: “I 
think it probable that these cervical 
sclerites represent the hindmost of the 
cephalic somites.” But we find no 
account of these sclerites that contains 
5 | _| more than a suggestion regarding their 
Fic. 20.— Lateral cervical scle- homologies. No evidence has been 
rites of Melanoplus. : 
brought forward to support any of the 
conclusions, beyond the position between the head and thorax 
occupied by these sclerites. We have been led to adopt the 
view put forth by Huxley for reasons that seem to us conclusive, | 
and which we will now state. 
The cervical sclerites are best preserved in the Orthoptera. 
In this order a variable number occur in the ventral wall of the 
neck ; two in each lateral wall ; and in some forms, two in the 
dorsal wall. 
Between the two lateral cervical sclerites there is in certain 
forms, as Melanoplus and Stenopelmatus, a prominent apodeme 
_ (Fig. 20, ap). This apodeme we regard as homodynamous with 
the lateral apodemes of the thoracic segments. Each of these 
 apodemes is an invagination between an episternum and an 
epimeron ; we, therefore, conclude that the anterior lateral 


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