174 Symmetrif of Egg and Symmetry of Embryo in the Frog 
and the entrance point. The sperm always enters somewhere in the animal hemi- 
sphere and the value of this angle therefore never exceeds 90°. 
(6) The angle between the sperm-entrance meridian and the lines ruled across 
the slide, obtained from (1) and (2) and the previously determined positions of the 
First Furrow and Plane of Symmetry on the slide. 
(7) The angle between Sperm-path and the First Furrow. By the Sperm- 
path I shall always mean the first part or ' penetration ' path of Roux. This is a 
conical streak of pigment, the base outwardly, the apex inwardly directed. It is 
evidently what is termed in cytological descriptions of fertilization, the entrance 
fuimel. It is formed when the sperm enters the egg by the aggregation of a clear 
hyaline substance (I describe what I have observed in another Amphibian — the 
Axulotl) about the anterior end — apical body or acrosome — of the spermatozoon. 
The substance streams into the interior of the egg — the phenomenon is probably 
0. 
o m 
D 
o 
Fig. 4. A. Meridional section of Axolotl egg just after the entrance of the spermatozoon. On the 
left is seen the entrance-funnel and sperm-sphere, containing the spermatozoon (j). ?, female 
pronucleus. P. B. polar bodies. 
B. Similar section a little later. In front of the Sperm-nucleus ( ) is the Sperm-aster. The 
entrance-funnel is marked by a streak of pigment ("penetration" path). 
C. Enlarged view of the spermatozoon and sperm-sphere of A. 
D. Enlarged view of the sperm-nucleus, and sperm-aster with the centrosome divided. 
The direction of the sperm-path is shown by the arrows. 
