448 RUTH J. STOCKING 



more irregular course, resembling in this respect those of Para- 

 mecium, Such a character is the 'beaded wing/ recently 

 studied by Dexter ('14). Lutz ('11) had previously investigated 

 an abnormal wing character in Drosophila, with results that 

 are still more similar to the conditions shown in Paramecium. 

 Lutz found that certain abnormalities of venation were herit- 

 able, but, as in Paramecium, the inheritance was not precise; 

 the abnormalities of parent and offspring might be diverse, but 

 the tendency to produce some sort of abnormality of venation 

 was inherited. Furthermore the proportion of individuals abnor- 

 mal, and the degree of abnormality, were modifiable by selection, 

 apparently through fine gradations. Lutz is of course working 

 with bisexual reproduction, which greatly complicates the inter- 

 pretation of the matter. Yet selection continued to be effec- 

 tive after ten generations of inbreeding, at which time it would 

 be expected that a homozygotic strain would have been reached, 

 if the character were dependent on typical Mendelian units. 



In many other cases abnormalities have been shown to follow 

 aberrant types of heredity; to attempt a general review of the 

 matter here would lead too far. 



