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THE AMERICAN NATURALIST. [Vol. XXXVIII. 



dence, nor have I been able to find any in support of this view. 

 There remains a consideration of the relation of these sclerites 

 to the primitive segmentation. I have called attention to the 

 fact that though Huxley, '58, does not make any definite state- 

 ment to that effect, the inference is strong thaf he regarded 

 these sclerites as representing the sternites of three preoral 

 segments. In fact, in referring to the Crustacea, he says that 

 the labrum represents the sternite of the antennary or third 

 somite. Viallanes, who likewise refers the labrum to the sternite 

 of his tritocerebral or third somite, seems to have attributed to 

 these sclerites a similar definite relation to the primary segmen- 

 tation. 



More recently Comstock and Kochi have independently arrived 

 at and very definitely present the view that the front, clypeus, 

 and labrum represent respectively the sternites of the first three 

 segments. In support of this view they lay much weight on 

 Viallane's statement that the labrum is innervated by the trito- 

 cerebrum. Since the front bears one or more of the ocelli, it is 

 obviously derived from the first or ocular segment. The inter- 

 mediate sclerite, or clypeus, would then belong to the second 

 segment. These writers also believe that the position of the 

 antennal rudiments is only apparently post-oral, — that in reality 

 the basal part of the antennal sclerites abuts against the pro- 

 cephalon. 



The embryological evidence, however, shows that the pro- 

 cephalon, and thus the sclerites 'derived from it, — the front, the 

 clypeus and the labrum, — belong to a single segment, the ocu- 

 lar or protocerebral. 



I have discussed elsewhere the question of the primitive posi- 



tion of the 



tinae, and have shown that in Blatta their rudi- 



ments are clearly post-oral at first. 



Even if we were to grant that the antennal rudiments are 

 only apparently post-oral, there can be no question as to the 

 primitive location of the second antennae and the third somite. 

 Vet the hypothesis derives the labrum from the sternite of this 

 segment. 



While I should attach great value to the innervation as a 

 criterion for determining the relation of sclerites to segments, I 



