474 
erate and play no further active part in either the 
developing or the adult spermatozoon. At the 
time of the breaking down of the nucleus, the large 
sphere with its astral system disappears, leaving 
only the contained centrioles and a mitochondrial 
mass which surrounded it. There are a great 
many of these centrioles and, lying close together 
at the periphery of the cell, they very soon divide 
and one half of the resulting granules begin to 
move across the cell. In this way a large bundle 
of very thick axial fibers is formed and its subse- 
quent growth greatly increases the length of the 
cell. Before it has reached its full growth, how- 
ever, the bundle splits down its long axis. Con- 
tinued growth causes each half of the bundle to 
pass to opposite sides of the cell. Here, by fusing 
and pushing out the cell wall, they eventually form 
the undulating membranes. The albuminous bodies 
first appear a short time before the bundle of axial 
fibers begins to split. They are formed by the 
filling up with albumen of previously existing 
vacuoles. At first these bodies are spherical, but 
later, through crowding, they become polygonal. 
The foregoing facts, relative to the development 
and the adult structure of these cells, would indi- 
eate that their function, if any exists, must be 
widely different from that of the ordinary sper- 
matozoa. Indeed, the evidence at hand is almost 
strong enough to make the application here of the 
word spermatozoon, in its specialized meaning, a 
misnomer. 
Reinvigoration Produced by Cross Fertilization in 
Hydatina senta: Davi D. WHITNEY, Wesleyan 
University. 
A report of experiments was given in which Dr. 
Whitney has reared rotifers for five hundred gen- 
erations by the parthenogenetic method. The fe- 
males of each generation laid eggs and these at once 
without fertilization by a male grew into females 
for the succeeding generation. Dr. Whitney ob- 
served two long experiments for about three years 
and found that these animals gradually became 
weaker and weaker by this maleless method of 
reproduetion and finally died out from general 
weakness if the experiments were carried on long 
enough. One of the races lived for 385 genera- 
tions and the other is still alive in the 503d gen- 
eration, but is in a very weak condition. When 
both races were alive and had reached a weakened 
condition males were produced from them and 
some inbreeding experiments were made in which 
eggs were fertilized by the sperm of the males of 
the same race. This was done in order to deter- 
SCIENCE 
[N.S. Vou. XXXV. No. 899 
mine whether fertilization would bring the race 
back to normal vigor. Several successive inbreed- 
ing experiments were made and only resulted in a 
slight amount of reinvigoration of either race. 
However, when the two weak races were cross- 
bred a great amount of reinvigoration occurred at 
once and the resulting race was as vigorous as 
any young normal race. 
To be published in full in the Journal of Ea- 
pervmental Zoology. 
External Agents and the Growth Period of the 
Egg in Hydatina senta: A. F. SHULL, Univer- 
sity of Michigan. 
It is not possible to reduce the proportion of 
male-producers in this species of rotifer by trans- 
ferring to manure solution eggs that have been 
laid in spring water, even though the manure solu- 
tion is strong enough to exclude male-producers 
when the rotifers are bred continuously in it. The 
nature of the females is determined, therefore, 
before they hatch. A female that has already pro- 
duced some male-producers, ceases almost imme- 
diately to yield male-producers if she is placed in 
manure solution. A female that has produced part 
of her family (all female-producers) in manure 
solution, may commence to bring forth male-pro- 
ducers almost immediately if she is transferred to 
spring water. The kind of female which will 
hatch from an egg is determined, therefore, within 
a period of two or three hours before the egg is 
laid. This period includes the entire growth of 
the egg and the formation of the single polar 
spindle. 
The complete paper will appear in the Journal 
of Experimental Zoology. 
Notes on the Inheritance of Barring: H. D. Goop- 
ALE, Station for Experimental Evolution. 
Some Reactions of Drosophila to Parallel Rays of 
Light: H. G. Kriss, University of Pennsyl- 
vania. 
The Drosophila were placed in a tube 8 inches 
long and about 1% inches in diameter. When 
placed in the light with the axis of the tube par- 
allel with the rays no characteristic reaction could 
be observed. When the axis of the tube was tilted 
to an angle of about 45 degrees to that of the 
rays the flies at once showed their characteristic 
orientation. When, however, the ommatidia form- 
ing the central mass of the eye were painted over, 
the flies no longer reacted in the normal way when 
the axis of the tube was placed at the 45-degree 
angle, but would do so when it was placed parallel 
to the rays of light. 
