APPENDIX A 



FURTHER REMARKS ON THE RELATION BETWEEN THE 

 SYMMETRY OF THE EGG, THE SYMMETRY OF SEG- 

 MENTATION, AND THE SYMMETRY OF THE EMBRYO IN 

 THE FROG. 



IN the measurements, referred to above (pp. 165-8), of the 

 angles between the plane of symmetry of the egg (as determined by 

 the position of the grey crescent), the first furrow and the sagittal 

 plane of the embryo, it was found (1) that there was a certain 

 tendency for the first furrow and the sagittal plane to coincide, 

 since in a large number of cases small angles preponderated over 

 large ones, the standard deviation of this angle from the mean 

 (which was practically = 0) being a = 40-39 + -65 ; (2) that 

 there was a much greater tendency for the plane of symmetry 

 and the sagittal plane to coincide, the standard deviation of the 

 angle between these two planes being a- = 29-75 + -63 ; (3) that 

 the first furrow tended either to coincide with or to lie at right 

 angles to the plane of symmetry, the standard deviation about 

 being 18-70 -60, that about 90 being 23-29 -86, the value 

 of or for all the observations being 47-90 + 1-19. The 

 correlation between the first furrow and the sagittal plane was 

 found to be p = -138 + -031, that between the plane of symmetry 

 and the sagittal plane p = -372 + -025, that between the plane of 

 symmetry and the first furrow p = -087 + -032. 



These results may be tabulated as follows : 



a- p 



} 40>39 >65 - - 13 8-<> 31 - 



Q- p and I 29-75 + -63. -372 + -025. 



Sagittal Plane. j 



Plane of Symmetry and J 47 . 9Q + Mg . 087 + 1()32 

 First Furrow. ) 



Full details of these results will be found in a paper in 

 Biometrika V. 1906. 



For the purpose of making these measurements the eggs were 

 placed in rows parallel to the length of glass slides, and the 

 angles measured between the various planes and lines ruled 

 across the slide. Such eggs compress one another by their jelly 



