410 E. I. WERBER 



interpretation which may be largely due to the insufficiency of 

 data at command at the present time. 



I also appreciate the justification of an objection often raised 

 against such attempts, namely that deductions regarding the 

 morphogenesis of monsters are uncertain, if based only on the 

 analysis of the end-products of such atypical development. 4 It 

 is, of course, obvious that certainty could here be gained only 

 by direct observation in vivo from the beginning of development 

 through successive stages. However, this direct method pre- 

 sents great difficulties in view of which it seems necessary to 

 take into account the inferential clues often furnished by the 

 analysis of already developed monsters. 5 The indirect evidence 

 thus gained is in accord with data established by direct obser- 

 vation of successive stages during atypical development in 

 many experiments in the lower animals. 



BLASTOLYSIS AS A MORPHOGENETIC FACTOR IN THE DEVELOP- 

 MENT OF DOUBLE MONSTERS 



"While attempting to account for the morphogenesis of 'mon- 

 stra per defectum' I (I.e.) have shown that in many of the em- 

 bryos of which a microscopical study was made there was un- 

 questionable evidence of either dissociation of tissues or of 

 dislocation of organs or of both. From these observations 6 

 the conclusion was drawn that we are here, manifestly, con- 

 fronted with some action (or actions) that tended to disintegrate 

 and to dissociate parts of the earliest embryonic primordium. 

 As the chief components of this complex process (blastolysis) 



'' 4 These objections were pointed out already by Rauber ('79-'80). 



5 Every teratological experiment in which, like the present, a chemical modi- 

 fication of the environment is employed, must be carried out on a great many 

 eggs, since their mortality is very high. This greatly increases the difficulty of 

 •continuous observation of the still surviving eggs of which probably no two de- 

 velop alike. Besides, the chemical processes and the alterations they are re- 

 sponsible for, elude direct observation. This is particularly true for the trans- 

 lucent egg of Fundulus. 



6 Similar observations were made by Mall ('08) who, however, dealing with 

 material not coming from experiments, did not attempt to account for the factors 

 underlying this shifting and dissociation of tissues which he correctly pro- 

 nounced as 'histolysis.' 



