386 JACQUES LOEB AND F. W. BANCROFT 
In these balsam preparations the first change which seemed to 
take place was a broadening of the sperm head with a decided 
increase in staining power. Then the sperm head gradually 
seemed to shorten and assume various irregular and sometimes 
angular shapes, still retaining its high staining power. Finally 
these small deeply staining heads seemed to become larger and 
vesicular, and typical nuclei were formed. Accordingly it would 
seem that when first formed these vesicles are so delicate that 
they cannot stand this technique without shrinking all out of 
shape. 
From these experiments we must conclude that in yolk and 
white of egg the spermatozo6n undergoes the transformation into 
a nucleus. We have not noticed any mitosis or asterformation 
and we are, therefore, not yet in a position to state that the 
spermatozo6n can undergo mitosis outside the egg. 
PLATE 1 
EXPLANATION OF FIGURES 
All the figures where drawn with a camera from preparations of chicken sperma- 
tozoa and nuclei into which the spermatozoa were transformed. 
The vesicles in figs. 1 to 6 all stain more lightly than the substance surrounding 
them, as is represented in fig. 6. To represent the preparations faithfully figs. 1-5 
should also have a background similar to that in fig. 6. All except fig. 4 are from 
preparations fixed in Flemming’s fluid. 
1 Chicken spermatozoa showing an early stage in the vesicle formation, 
and the beginning of the bending of the spermatozo6n in the middle-piece region. 
Sperm kept in white of egg two hours, forty-five minutes. Stained and examined 
in Herla’s malachite green and vesuvin mixture. X 1620. 
2 Spermatozoa with vesicles as in fig. 1 but more eompletely bent on them- 
selves in the middle-piece region. All of the loops contain vesicles which are seen 
exactly from the side in a and ¢ and slightly from the edgeinb. From same prep- 
aration as fig. 1. X 1620. 
3 Spermatozoa similar to those im fig. 2 but seen edge on. From same prep- 
aration as figs. land2. X 1620. 
4 Spermatozoén showing the maximum development of the vesicle before 
the bending of the sperm head begins. Sperm kept in yolk for about four hours. 
Killed, stained and examined in Herla’s. X 640. 
