ORIGIN OF MONSTERS 503 



which, while being outside of the 'cyclocephaUc group/ yet ex- 

 hibits ample evidence that it owes its formation to like morpho- 

 genetic factors. 



a. Synophthalmia hilentica. One of the embryos which we 

 have chosen for the presentation of this malformation is seen 

 in toto in figure 3 (p, 488). The eyes are large, not fused, but 

 very closely adjacent. On microscopic examination it is seen 

 that in anterior sections the eyes are separate (fig. 63) . If, how- 

 ever, the whole series be examined, it is found that at about the 

 le^'el at which the lens appears in the sections, the medial mar- 

 gins of the eye-bulbs begin to blend; and when followed more 

 posteriorwards this fusion becomes so intimate as to manifest 

 itself in a unition of the retina of one eye with that of the other. 

 The eyes appear to be otherwise normal in structure and two 

 optic nerves are present which are seen to enter the optic lobes 

 after having formed a chiasma (fig. 64). 



Examination of the entire series of sections of this embryo 

 suggests that the injury sustained by it which is responsible for 

 its ophthalmic malformation was apparently restricted to the 

 most anterior part of the future embryo's body. This is evi- 

 denced by the following data. The abnormalities such as are 

 found to characterize this embryo concern the mouth, the olfac- 

 tory organ and the most anterior part of the brain, viz., the 

 fore-brain. As seen in figure 3 the mouth is a typical proboscis, 

 and the olfactory pits are in sections seen to be perfectly blended 

 into one large pit (fig. 63). The fore-brain is abnormal in struc- 

 ture and unpaired (fig. 63), while the mid- and hind-brain are 

 bilaterally s^mimetrical and apparently normal in other respects 

 (fig. 64). On following out the whole series of sections no other 

 abnonnality can be detected. The injury sustained is thus very 

 clearly seen to be restricted to the embryo's anterior end. Its 

 probable nature and its morphogenetic consequences will be 

 pointed out in the course of the following description of other 

 embryos where a like teratogenetic principle seems to obtain. 



6. Synophthalmia unilentica. The embryo selected for the 

 description of this deformity is from the same experiment as the 

 preceding one and was twenty-four days old when killed. In 



