192 An7ials Entomological Society of America [Vol. X, 



by Riley, 1904, in his table of the parts of the head of a Blattid 

 embryo. Riley offers absolutely no proof whatsoever, either 

 in his text or figures, for such an assumption, and it is the 

 more inexplicable from the fact that he definitely states that the 

 "pleurite" (i. e. the embryologists' term for pleuron) of the 

 labial segment is in the posterior portion of the embryo's head 

 capsule. The only explanation which suggests itself, is that 

 he must have been unaware of the existence of intersegmental 

 regions III and V (Fig. 1), homologous with the neck plates, and 

 situated between the true segments, in the lower insects, and 

 was thus unable otherwise to account for the presence of the 

 intersegmental plates forming the neck region, unless they 

 were to be regarded as representing the labial segment. Since 

 I have not examined Dr. Riley's material, I do not know what 

 evidence it offered for assuming that the neck plates represent 

 the embryonic labial segment, but, while studying in Berlin, 

 Prof. Heymons allowed me to look over his embryological 

 material, in which I was unable to find any indications what- 

 soever that the neck plates represent the embryological labial 

 segment; and in view of the direct embryological evidence 

 that the labial segment is included in that portion of the head 

 capsule to which the labium is articulated, I am forced to 

 consider that the including of the neck plates in the labial 

 segment in Dr. Riley's paper, is a minor error in an otherwise 

 extremely carefully conducted and valuable embryological 

 investigation. 



I have perhaps laid too great emphasis upon a "side issue" 

 of Dr. Riley's paper simply because, in searching through the 

 appended list of reference works, his is the only recent article 

 I could find, containing original embryological data, in which 

 the neck plates are referred to as the labial segment; and on 

 this account, I have inferred that recent investigators have 

 reference to his work, when they state that there is embryolog- 

 ical "proof" that the neck plates are to be regarded as the 

 "labial or microthoracic segment." It seems incredible that 

 any one can seriously put forth as "proof" the mere fact that 

 some investigator has arbitrarily designated the neck plates as 

 the labial segment in his table of the parts of the head, without 

 giving any reasons for so doing, but such seems to be the case, 

 unless these entomologists have reference to some other work 

 which I have not seen. 



