ORIGIN OF MONSTERS 493 



the api^earance of an elongated snout or proboscis-like structure. 

 On sections of such embryos it was found that this 'proboscis'- 

 mouth is apparently capable of functioning, for the continuity 

 of the oral cavity with the pharynx and oesophagus is nowhere 

 interrupted. 



Stockard ('09) who has also obtained this abnormality of the 

 mouth in cyclopean embryos with magnesium chloride in the 

 same material suggests that 



this condition is due to the fact that the single antero-median eye 

 occupies the position normally assumed by the mouth and thus ob- 

 stmcts the usual forward growth of its structures. The mouth, there- 

 fore, remains ventro-posterior to the eye and grows downward, pre- 

 senting the proboscis-like appearance. 



This interpretation of the 'proboscis'-mouth as secondary to 

 the 'cyclopean' condition does not appear to be justified, for I 

 have recorded the occurrence of this anomaly of the mouth not 

 only in cyclopean and synophthalmic, but also in asymmetrically 

 monophthalmic and in some two-eyed microphthalmic embryos 

 (fig. 21). In neither of such cases can the eye or eyes be said 

 to occupy the position which is normally taken by the mouth. 

 Moreover, the very opposite may occasionally be found to occur, 

 viz., that in some asjanmetrically monophthalmic embryos (fig. 

 15) the mouth may take the place which should normally be 

 assumed by the lacking eye. There is good reason to believe 

 that the 'proboscis'-mouth results from approximation and par- 

 tial fusion of the potential anlagen of the maxillary and man- 

 dibular arches, following an injury which has destroyed inter- 

 mediate parts. This becomes strikingly evident on examination 

 of sections. 



Our \T.ew is further strengthened bj^ Spemann's ('04) findings 

 who, by constricting amphibian eggs, has produced ophthalmic 

 deformities and the 'proboscis'-shaped mouth in the same embryos. 

 In Spemann's experiments the destruction of material inter- 

 mediate between the potential eyes, the potential maxillary and 

 mandibular arches could not, by any means, be doubted, for here 

 the relation between a well defined mechanical injury and the 

 resulting morphological defect is evident. Moreover, on exami- 



