1917] Veracervix or Neck Region In Insects 193 



Now the neck region of an insect is no more a part of the 

 head capsule than the seven cervical vertebrae of mammals 

 are a part of the skull, and it would therefore be wholly incorrect 

 to say that the head of an insect is composed of six segments, 

 if the sixth, or labial segment, remains behind to form the neck 

 region, which is situated back of the head region. It is thus 

 rather surprising to have these entomologists refer to the head 

 of an insect as composed of six segments (including the labial 

 segment) and in the same breath assert that the neck plates 

 behind the head of such an insect are the labial segment. This 

 is assuredly not in conformity with the laws of physics, which 

 assert that a single body cannot occupy two different positions 

 at one and the same time! If the labial segment is in the head 

 region, it simply cannot be in the neck region behind the head 

 region; and when such embryologists as Heymons, Holmgren, 

 Hirschler, Hoffman, Philiptschenko, Strindberg, and every 

 other recent embryologist, with the exception of Riley, are 

 unanimous in asserting that the labial segment is in the head 

 capsule, it would appear that there is some reason for con- 

 sidering that the labial segment is really in the head capsule 

 and not in the neck region behind the head! Heymons and 

 Holmgren have very carefully traced out the portions of the 

 head which are formed by the embryonic labial segment, and 

 I can see no reason for regarding their work as wholly false, 

 especially since it is borne out by the facts of comparative 

 anatomy and is in accordance with the known zoological 

 phenomena. We are thus justified in stating that the only 

 actual embryological proof thus far brought forward, con- 

 clusively demonstrates that the labial segment enters into the 

 composition of the head capsule, and consequently the neck 

 plates must be interpreted as intersegmental plates between 

 the real labial segment and the prothoracic segment, homol- 

 ogous with the other intersegmental plates between the other 

 thoracic segments. 



Those who maintain ' that the neck plates are the labial or 

 microthoracic segment, must bring forward some actual proof 

 for their claim. They must prove the falsity of the embryo- 

 logical evidence brought forward by such embryologists as 

 Holmgren, 1909, who have shown that the embryonic segment 

 depicted in Fig. 2 is the labial segment, or they must explain 

 in some other way the presence in the head capsule of an 



