THE MUTATED GENE 49 



The first step to link these facts with the problems that we are 

 studying here was taken by Newman (1908-1917) when he found 

 that the same type of monsters could be produced by crossing 

 widely distant forms of teleosts. Here, then, a genetic agency was 

 found to have a parallel effect, which now brings this set of facts 

 close to the problem of the phenocopies. Here belongs also a 

 finding by Montalcnti (1933), who reported numerous abnormali- 

 ties produced by crossing species of toads all of which may be 

 attributed to the effect of asynchrony of developmental rhythms. 



The foregoing interpretations are still better supported by 

 cases in which a single Mendelian gene produces effects very much 

 like the ones described; there is the case of Little and Bagg (1924), 

 of monsters in mice supposed to be inherited in a simple Mendelian 

 way; another somewhat different one by the same authors (1929) ; 

 a case of Wriedt and Mohr (1928) of such a type in cattle. Also, 

 Little and Bagg in analyzing the abnormalities produced in 

 X-rayed rats reach conclusions of a similar type. They find 

 that the defects are in most cases the consequence of extravasates, 

 produced at different times, which interfere with the normal rate 

 of differentiation of the respective organs. In some respects, 

 the best analyzed case, though not so simple on the genetic side 

 and not studied embryologieally, is the one found by Wright, 

 the case of otocephaly in guinea pigs (Wright, 1934c; Wright 

 and Wagner, 1934; Wright and Eaton, 1933). This heritable 

 abnormality consists in a graded series of changes at the anterior 

 end, beginning with a reduction of the lower jaw. (2) Then 

 the ears are joined below the jaw by naked skin; (3) then there is 

 only a single ear opening on the throat; (4) the mouth and upper 

 incisors are lost; (5) the nostrils fuse; (6) the eyes become fused 

 more or less below the proboscis; (7) and the fusion becomes 

 complete. (8) Then the proboscis is lost; (9) the eye also; (10) 

 also the ear opening; (11) and finally no head is left except a small 

 median ear. Figure 16 illustrates these grades. 



This type of monstrosity is inherited, though not in a simple 

 manner, a fact that does not concern us here, however, except 

 that we are not dealing with the effect of one mutant gene but 

 with a combined effect of, perhaps, two. There is no comparable 

 phenocopy in mammals, but, as we have already reported, in lower 

 vertebrates monsters have been produced by experimental 

 treatment of early embryonic stages which closely resemble these. 



