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THE AMEBIC AN NATURALIST [Vol. XLVII 



old, having been in a constant tremor since its birth; 

 another lived for nine days but whenever it attempted to 

 walk it was seized with spasmodic contractions ; the third 

 specimen exhibited the same nervous manifestations and 

 was completely eyeless. This animal died eight days 

 after birth and an examination of the brain showed an 

 entire absence of optic tracts, as may be seen in Plate 1A. 



In the development of this animal it is probable that 

 the optic vesicles were supj:tressed and never arose from 

 the brain. Thus, no eyes, optic nerves, or optic tracts 

 could have formed. This particular eyeless condition in 

 these experiments is of interest since one is readily able 

 to suppress the origin of the optic vesicles in fish and 

 chick embryos by similarly weakening the embryo with 

 treatments of alcohol, ether, etc. 



The mother of these offspring was remated with her 

 brother, but she died six weeks later, not becoming preg- 

 nant. She was in an emaciated condition but had always 

 been less than half normal weight. 



The three extremely weak and defective offspring were 

 doubtless due to the fact that both of their parents had 

 similarly weakened or injured constitutions, having re- 

 sulted from a single mating of a normal female with an 

 alcoholized male. The eyeless offspring and the other 

 two nervous non-viable individuals should not be inter- 

 preted as due merely to the fact that their parents were 

 brother and sister. Several normal matings of brother 

 and sister have been made during the experiment and 

 perfectly healthy offspring have been produced. In the 

 studies of heredity conducted on guinea-pigs brother and 

 sister are crossed with impunity, in no way weakening 

 their offspring. The significant point in the present con- 

 sideration is that the two animals coining from the same 

 mother and treated father may have had similar weak- 

 nesses or defects and the combination of two such indi- 

 viduals resulted in offspring which exhibited these defects 

 to a more decided extent. The three animals were far 

 more defective than their parents and owed their defects 



