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capillary — and carries with it the spermatozoon, and at the same time sweeps 
before it a good deal of the superficial pigment (Fig. 4 A). This pigment remains 
when the clear substance has disappeared as the visible sperm tract (Fig. i B and 
Fig. 5). 
At the inner end of the entrance-funnel (if I may resume here very briefly 
what occurs in the Axolotl) a sperm-sphere — or yolk free area — appears round the 
middle piece (a modified centrosome), the sperm-head having meanwhile been 
rotated through 180" so that the middle piece is inwardly directed (Fig. 4 ('). 
Radiations appear round the sperm-sphere which then becomes the sperm-aster, 
and the sperm-nucleus — developed from the sperm-head— preceded by its aster 
travels towards the egg-nucleus. As it does so its centrosome divides (Fig. 4 D) 
at right angles to the direction in which it is now moving. This direction 
(the 'copulation' path of Roux) may, but need not, be in tlie same meridional 
plane with the entrance funnel, and when it is, it may but need not be in the same 
straight line as the other, for the entrance funnel may be directed towards the 
Fig. 5. Projections in an equatorial plane of the various relations of Sperm-path to First Furrow. 
A. The whole path included in the Furrow. 
B. The whole path parallel to the Furrow. 
C. The "penetration" path turned away from, the "copulation" path parallel to the Furrow. 
D. The Sperm-path inclined towards the Furrow at a large angle. 
