278 Proceedings of the Royal Physical Society. 



pre-m axillary bones, and in none of our specimens did we 

 find these bones in tlie alveolar arch. The upper lip and the 

 superior alveolar arch are developed from three processes, 

 viz., the fronto-nasal, which passes down in the middle line, 

 and the maxillary processes, which extend forwards and 

 inwards on each side, and blend with the fronto-nasal. 

 Although the parts developed from the fronto-nasal process 

 are absent, yet there does not appear to be ever a cleft in the 

 middle of the upper lip or superior alveolar arch. Indeed, 

 in the human foetus, and also in the other specimens, not 

 only did the superior maxillary bones meet in the mesial 

 plane in front, but they were firmly united by bone. 



Kepresentatives of the intermaxillary bones do not appear 

 to have been detected in the anterior part of the proboscis. 

 As the incisor teeth are normally found embedded in the 

 intermaxillary bones, their complete absence from the superior 

 alveolar arch, as in the human cy clops («.), is not surprising. 



As several of our specimens show, a single central incisor 

 tooth is sometimes found in animals fixed in the gum in 

 front of the superior maxillae, although the intermaxillary 

 bones are absent. As the teeth are developed from the 

 epiblast lining the mouth and the subjacent mesoblast, the 

 presence of incisor teeth, independent of the presence of a 

 fronto-nasal process and intermaxillary bones, is easily 

 understood. We have looked carefully for what Hannover 

 describes as the " persistent canal of Kathke," but can find 

 no traces of it. As most of our specimens were animals, 

 we are not surprised at this, for Hannover himself describes 

 it only in human Cyclopeans. 



These cyclopean monsters do not, as a rule, survive beyond 

 a few minutes after birth. This is usually attributed to their 

 defective cerebral development being inconsistent with the 

 maintenance of their vital functions. Such does not appear 

 to be an altogether satisfactory explanation, for the base and 

 posterior portions of the brain are usually well developed. 

 In our opinion, a more probable cause of death is the 

 absence of the normal air passages between the exterior and 

 the pharynx, so that the newly born animal must breathe, 

 if at aU, by the mouth. 



