570 E. I. WERBER 



of a fragment of, either, ophthalmohlastic or potential interocular 

 material and not to an inhibition as was held by Huschke and 

 Dareste and is 7iow postulated by Stockard. 



Only such cases of anophthalmia, where on microscopic exami- 

 nation rudiments (ill-differentiated optic vesicles or cups) are 

 found, form an exception to this rule. Here an inhibition is 

 assumed, due to a decrease of the chemical capacity for develop- 

 ment (chemical exhaustion). 



9. The frequent occurrence in these experiments of terata of 

 the eyes (or the anterior part of the head) only is regarded as 

 being due to the highest degree of susceptibility of that part of 

 the earliest embryonic primordium, which eventually becomes 

 the embryo's anterior end (animal pole). This assumption sup- 

 ported by many data, is based on Child's discovery of a definite 

 susceptibiUty gradient ('metabolic gradient'-Child) along the 

 chief body axis of many animals from various phyla. 



10. The numerous meroplasts recorded and especially such 

 teratomata as the 'sohtary eye' and the 'isolated eye' point to 

 a very high degree of capability of parts of the embryonic pri- 

 mordium for independent development and differentiation (self- 

 differentiation — Roux) . 



11. While the occurrence in these experiments of various 

 duplicities would seem to point to a relatively high prospective 

 potency of parts of the teleost egg, the latter decreases very 

 rapidly, for at an early stage (the Rand-s^oilst-stage or thereabout) 

 these parts are already specifically predetermined as early (un- 

 differentiated) anlagen of some organs. If at this stage a frag- 

 ment be eliminated the result will be a defect of a corresponding 

 organ or part of the body. Accordingly the teratogenetic time 

 limit must be regarded as very brief, and especially so in the 

 case of duplicities. 



12. The results obtained tend to justify the hypothesis on 

 which the experiments were based, namely that parental meta- 

 bolic toxaemia may be the cause, or, at least, the chief cause 

 underlying the origin of monsters. 



DECEMBER 24, 1915 



