APPENDIX A 307 



From this it is clear that there is a very close relation indeed 

 between the point of entry of the spermatozoon and the direction 

 of the first furrow, especially when the disturbing effects of pres- 

 sure and gravity are removed. There is, however, little relation 

 between the sperm meridian and the plane of symmetry even 

 under the most favourable circumstances, and when the condi- 

 tions are not favourable the correlation is negligible. There is 

 however (in the 8 series) a considerable correlation (p -479 + '070) 

 between the sperm-path and the plane of symmetry. It should 

 be remembered, however, that all these eggs were exposed to the 

 light. From what we know of the effect of this agent upon the 

 direction of the symmetry plane, it would not perhaps be too 

 bold a hazard to surmise that in darkness there would be a 

 correlation between the sperm entrance and the plane of sym- 

 metry. 



Even after the removal of this disturbance there remain 

 factors which interfere with the completeness of the correlation 

 between these planes; these must probably be looked for in 

 the incomplete radial symmetry of certain eggs due possibly 

 to pressure in the uterus and to the slight squeezings and dis- 

 tortions the eggs may be subjected to when they are being taken 

 from the Frog. 



It will be seen that the relation between the sperm-path and 

 first furrow is closer than that between the latter and the sperm 

 entrance. This is because though the furrow may be placed to 

 one side of the entrance point, it may still be parallel to the path, 

 or, if not to the ' penetration ' path then to the inner or ' copu- 

 lation ' path, as observed by Roux. This ' copulation ' path is 

 usually observed when the penetration path is turned away from 

 the first furrow, that is, when it has not been directed towards 

 the egg-axis. 



The same data give the position of the point or of entrance 

 with regard to the direction of ' pressure ' and ' gravitation 

 symmetry'. In the (a) series the sperm tends to enter in 

 the direction of ' pressure ', that is, on that side of the egg on 

 which it is in contact with its neighbours. Hardly a single 

 spermatozoon enters on that side of the egg on which the white 

 pole had been turned up, and very few on the opposite side. 



X 2, 



