262 HANS PRZIBRAM 



antero-posterior differentiation falls upon the meridian of fer- 

 tilization we may justly suppose that the grouping of anterior 

 and posterior anlagen is also produced through fertilization. 

 The symmetry of the right body -side would be developed on 

 the right of the meridian passing through the posterior and dor- 

 sal poles, while the symmetry of the left body-side would develop 

 on the opposite side. Strictly bilaterally symmetrical animals do 

 not afford the means of discerning as to whether similar or dissimi- 

 lar "Anlagen" are distributed in both sides of the body. 



Ill 



I We must come back now to the topic of minor asymmetry and 

 I to consider such objects which may be propagated through several 

 /generations, because through the study of heredity we must find 

 I out if the asymmetry, manifested on a certain side of the parents 

 I body either in the development there of a new character or in 

 the dropping out of a character, will tend to reappear also in 

 the offspring; and, furthermore, whether the asymmetry will 

 reappear on the same side of the body, or on any side quite re- 

 gardless of the condition observed in the parents. The phenom- 

 enon of heterochromy of the eyes presents such a case of asym- 

 metry, as it is found for instance in certain cats with one yellow 

 and one blue eye. From my lists of pedigrees of these cats T 

 made the following deductions : 



1, Heterochromy as such may be inherited; 2, in this case the 

 offspring does not always have the yellow eye on the same side 

 of the body as its parents; and 3, the color of one eye of the ances- 

 tor may in the offspring appear in both eyes. 



Other authors, for example Castle, found it impossible to fix 

 color-patches tending to asymmetrical distribution in descen- 

 dants of guinea pigs selected for this purpose. On the contrary the 

 symmetrical hood of piebald rats, which extends over the anterior 

 and dorsal half of the animal is inherited as an unchangeable 

 unit-character in strict accordance with Mendel's rule. 



Apparent exceptions to Mendel's rule frequently appear in 

 those structural characters which are often asymmetrical, as for 



