212 CHARLES R. STOCKARD AND GEORGE N. PAPANICOLAOU 



The experimental modification of the inheritance of definite 

 characters by a treatment of the germ cells is a future possibility. 

 It must be recognized, however, that one is able to produce 

 grotesque monsters by a treatment of eggs or spermatozoa, and 

 yet all of the known characters which Mendelize in such an in- 

 dividual may be expressed in a perfectly normal fashion. This 

 may be due to the fact that comparatively few such characters 

 are known. Aside from the future definite modifications of 

 inheritance, it would seem from the present study that the 

 'general qualities,' for lack of a more suitable term, of an or- 

 ganism may be affected, on account of an experimental modi- 

 fication of the germ plasm from which it arose. The modifi- 

 cation may have taken place several ancestral generations ago. 

 This is really the inheritance of pathological conditions which 

 were induced upon and transmitted by the ancestral germ plasm. 

 Such a type of inheritance is no doubt important in its relation 

 to the normal processes of development and inheritance. 



15. GENERAL CONSIDERATIONS 



A discussion of the literature bearing on the influence of various 

 chemical substances on the egg and spermatozoon has been given 

 in former papers of this series, particularly Stockard ('12 and 

 '13). In all cases only the effects of the treatments on the zygotes 

 immediately resulting from the modified spermatozoa or eggs 

 have been studied. There has been no experimental investiga- 

 tion of later generations arising from the affected specimens. 

 And indeed, in almost all cases the developing individuals were 

 lost during early embryonic stages as in the X-ray experiments 

 of Bardeen and the radium studied of Oskar Hertwig which are 

 the most satisfactory investigations on the direct injury of the 

 sperm. These experiments really supplied no available material 

 for an investigation of the inheritance or transmission of the 

 induced defective conditions. 



Since the beginning of the present experiments other studies 

 have been recorded which bear more directly on the results con- 

 sidered in the foregoing pages. Of particular interest in connection 

 with our supposed differential effects of the alcohol treatment on 



