Volume III 
NOVEMBER, 1904 
No. 4 
MERISM AND SEX IN " SPIN AX NIGER." 
By R. C. PUNNETT, M.A., Fellow of Gonville and Caius College and Demonstrator 
of Comparative Anatomy in the University of Cambridge. 
CONTENTS. 
PAGE 
I. Introduction 313 
Material and Methods 314 
Sexual Dimor^jhism 318 
The Numerical Proportion of the Sexes 321 
II. Variation and Correlation 321 
Meristic Variability 321 
Variability in Difierent Regions 326 
Correlated Variability in the Meristic Series 326 
Growth Changes 333 
Variability in the Girdle Canals 333 
The Hypothesis of Excalation 334 
On Intercalation 337 
Random Increase and Decrease of Segments. Note by K. Pearson . 338 
III. Heredity of Meristic Characters 341 
Fraternal Correlations 341 
Absence of Differential Sex Variability in Mothers .... 343 
Parental Correlations 344 
IV. Summary 345 
Appendix of Tables 348 
I. Introduction. 
In spite of the mass of literature steadily accumulating upon the subject, the 
question of the origin of limbs still remains one of the most vexed problems in 
vertebrate morphology. The gill-arch theory of Gegenbaur and the side-fold 
theory with which the name of Balfour is most closely associated each have their 
supporters. Both theories are so elastic that each without undue stretching may 
be made to cover all the facts at present known with regard to the comparative 
Biometrika in 40 
