ON THE PRODUCTION OF MONSTERS BY 

 HYBRIDIZATION. 



H. H. NEWMAN. 



Of late there have appeared several papers that deal with the 

 production of monsters in teleosts, especially in the common 

 mud-minnow, Fundulus heteroclitus. The papers of Kellicott 

 ('16) and Werber ('15 and '16) have been especially interesting 

 because they deal with the same type of monster that I have 

 been studying incidentally for more than ten years and that I 

 have described and discussed in several different papers dealing 

 with development and heredity in fish hybrids. 



In 1908 I published the results of intercrossing Fundulus 

 heteroclitus and F. majalis (Newman, '08). In the cross F. 

 heteroclitus X F. majalis I called attention to the various types 

 of monsters, noting especially those types in which the head and 

 eyes developed and the body was relatively inhibited, and those 

 in which head development was inhibited and body was relatively 

 normal. 



The wide range of variability in the results of crossing two 

 individuals of different species was emphasized. A long list of 

 conditions was given ranging from extreme subnormal eggs that 

 failed to cleave, up to markedly supernormal individuals that 

 are hardier and better equipped to live than individuals of either 

 pure strain. In subsequent papers (Newman, '12 and '14) I 

 called further attention to the graded series of teratomata 

 resulting from one set of eggs fertilized by sperm from a single 

 male. 



In general it was shown that in hybrids between closely allied 

 species (homogenic hybrids) the rate of development of a con- 

 siderable percentage of individuals was accelerated, but that in 

 all heterogenic hybrids there is a more or less marked retardation 

 of developmental rate from the earliest cleavage stages on. Even 

 in the case of homogenic hybrids, the retarded individuals are 



always abnormal. 



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