CONTRIBUTIONS FKOM THE ZOOLOGICAL LABORATORY OF THE 



MUSEUM OF COMPARATIVE ZOOLOGY AT HARVARD 



COLLEGE, E. L. MARK, DIRECTOR, No. LXXIII. 



STUDIES IN MORPIIOGEXESIS, VI. 



A CONTRIBUTION TO THE QUANTITATIVE STUDY OF CORRE- 

 LATED VARIATION AND THE COMPARATIVE 

 VARIABILITY OF THE SEXES. 



By C. B. Davenpokt and C. Bullard. 



Presented October 14, 1896. 



The following quantitative study of variation is based upon counts of 

 the Miillerian glands of the fore legs of 4,000 swine. Our attention was 

 directed to these glands as favorable objects of study by Gertrude Grotty 

 Davenport, who had already collected some data concerning their varia- 

 bility. These data, together with valuable suggestions derived from her 

 own experience, she generously placed at our disposal. 



The positions of the Miillerian glands ai-e indicated upon the wrist by 

 large openings or pits, about 1 mm. in diameter, which are found only 

 upon the inner aspect of the fore legs. The number of pits is variable. 

 Where there are several they occur, for the most part, in a single row 

 trending somewhat obliquely to the long axis of the leg. 



Of the 8,000 legs examined, the arrangement of the glands was studied 

 on only 2,000 legs, 1,000 male and 1,000 female. The total number of 

 glands on a single leg varies from to 10. When the number is large, 

 some of the glands are frequently found outside the main row. In no 

 case have we found more than nine glands in one row. We may call 

 those lying outside the main row lateral glands. The lateral glands 

 usually (six exceptions) occur at the upper (proximal) end of the series. 

 Their number does not usually exceed two, but in a single case we have 

 found four. These four glands lay in a secondary row parallel to the 

 main row, which contained five glands. In one other case, where three 

 lateral glands were found, these lay parallel to the main row of five. 

 When there are two glands they may lie .either in a line parallel with 

 the main row, or make any angle up to 90° with it. Lateral glands 

 occur more rarely when the total number of glands on the leg is small, 

 but we have found one extreme case in which the only two glands on the 

 leg occurred side by side, i. e. in a transverse row. 



