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PROCESS OF FECUNDATION. 65 
to the neck cells and stop over these and continue to gradually revolve 
around and around, apparently in the process of crowding into the egg 
cell. In fecundation the entire spermatozoid unchanged swims into 
the egg cell, passing between the ruptured neck cells. The entrance 
tube is very narrow compared with the size of the spermatozoid, and 
the latter must be greatly stretched out in accomplishing the passage. 
It is certain that they pass through into the egg cell entire, as they 
have in many instances been found in the egg cell having their normal 
shape. Several spermatozoids commonly enter each egg cell, two and 
three having been found in very many instances. Only one of these 
takes part in fecundation, and the others may be found presenting a 
perfectly normal appearance or in some stage of disintegration. Those 
not concerned in fecundation may usually be found in the upper part of 
the egg cell between the wall and the cytoplasm, which is slightly con- 
tracted away from the wall in the majority of the writer’s preparations. 
In some instances they seem to have crowded against the cytoplasm 
of the egg and caused a noticeable indentation (figs. 55 and 70). Occa- 
sionally one of the spermatozoids not concerned in fecundation pushes 
for a short distance into the contents of the egg cell, but such sperma- 
tozoids do not mingle with the protoplasm of the egg cell, as they 
are always found in such cases to form distinct bodies, which stain 
very differently and remain intact until long after fecundation has 
taken place. The spermatozoid which reaches the egg cell first would 
seem to be the one which causes fecundation. That one which is 
utilized in fecundation swims into the cytoplasm of the egg cell for a 
short distance, where it comes to rest and undergoes change. The 
nucleus slips out of its cytoplasmic sheath and passes on alone from 
this point to the egg nucleus, with which it unites. The spiral cilifer- 
ous band, which forms such an interesting part of the spermatozoid, 
remains at the apex of the egg cell in the place where the nucleus left 
it. In very numerous instances just after fecundation it has been dis- 
covered in this position, and there can be no doubt that this process is 
the one normally occurring. It shows very plainly and presents nearly 
the original form of the spermatozoid, but is alwaysstretched out much 
more than in the normal spermatozoid. The band lies free in the 
cytoplasm of the egg cell, and the sections of the spiral, with the num- 
erous cilia radiating from them, are frequently very distinct and can 
be easily photographed (fig. 69). 
The method of the escape of the nucleus from the body of the sper- 
matozoid can only be conjectured. It would seem, however, that the 
rapid boring of the apical or spiral end into the egg cell may cause too 
great a pressure on the large body of the spermatozoid, resulting in 
its bursting and freeing the nucleus, while the cilia motion continues 
probably some time longer, carrying the band farther along and freeing 
the nucleus from any hindrance by it. The apex or spiral end of the 
5526—No. 2—01——5 
