ORIGIN OF MONSTERS 537 



antero-median portion of the head pnmordium may, and, no 

 doubt does, vary in quantity and location. The eUminated 

 'wedge' may involve an antero-lateral fragment only, which con- 

 tains the ophthalmoblastic material of one side and in this case 

 the embryo will lack one eye (asymmetric monophthalmia) . 

 Or, the 'wedge' may be a very broad and short one and involve 

 parts of the ophthalmoblastic areas of both sides as well as a 

 small antero-median portion. The result will be an embryo mth 

 small eyes, as a rule nearer each other than are normal eyes, 

 and with deformities of the mouth (often proboscis-shaped) and 

 the olfactory pits (microphthalmia). 



Neither the unwarranted assumption of a single median eye 

 anlage and an inhibition of its 'developmental vigor' (Stockard) 

 nor, much less yet, degeneration due to deficiencies in the circula- 

 tory system as Loeb CI 5) assumes, can be expected to solve the 

 difficult problem of teratophthalmia. For, these deformities are 

 clearly due to a defect of the undifferentiated embryonic primor- 

 dium. With the possible exception of such cases of anophthalmia 

 (in which on sectioning deeply buried rudimentary eyes aie found) 

 where an inhibition cannot be excluded, all eye malformations 

 can be accounted for by a blastolytic defect. And the localiza- 

 tion of the latter can, in turn, be understood, when we assume 

 the presence of an antero-posterior axial susceptibility gradient, 

 which Child's investigations have made so highly probable. 



D. DEFORMITIES OF THE BRAIN 



In nearty all pathological embryos recorded in our observa- 

 tions the central nervous system is more or less deformed. 

 No detailed study of the malformations of this system has yet 

 been made, and the few observations which will be recorded 

 at this place pertain largely to the brain in teratophthalmic 

 embryos. 



In our description of ophthalmic deformities same malforma- 

 tions of the brain have already been pointed out (cf. pp. 503, 

 506, 508, 509, 511, 512, 513, 515 and 520). It was shown that 

 in synophthalmic and cyclopean monsters the forebrain is single, 



