PRODUCTION OF MONSTERS BY HYBRIDIZATION. 



313 



and form are mixed together in a single cell, than when they are 

 all of the same kind. Whatever the primary cause of abnormal 

 development may be, the most obvious early effect is a lowering 

 of developmental rate and it is on this point that the similarity 

 exists among all of the experimental results heretofore discussed. 

 Since we are dealing primarily with rates of metabolism, we 

 shall doubtless find, as Werber has suggested, that the morpho- 

 genesis of monsters in teleosts is simply a special case of form 

 regulation similar to those recently described and discussed by 

 Child ('15 and '16) for sea-urchins, in which he demonstrates 

 the effectiveness of the axial metabolic gradients as dynamic 

 factors in the development of various types of monsters. He 

 has been able to "control and modify development by means 



of the differential action of external factors on different regions 

 of these gradients." 



It is my belief that an application of the principles enunciated 

 by Child serve to rationalize the results of heterogenic hybridiza- 

 tion as well as those produced by chemicals and by low tempera- 

 tures, and since Werber merely suggested the possibility of 

 explaining ophthalmic anomalies by this theory and failed to 

 apply it in any far-reaching way to the other various types of 

 monster he was dealing with, it seems w T orth while to give the 

 theory a thorough trial in this field. 



