234 THE AMERICAN NATURALIST. [Vor. XXXV. 
fluid on a glass slide, and watched under the microscope. A certain 
number of the eggs developed (without fertilization) upto the morula 
stage. The fluid was found to be effective in causing the develop- 
ment of unfertilized eggs, even when ten hours old. Control lots 
of eggs placed in sea water or in distilled water did not develop at 
all. The sperm extract made in sea water worked better than that 
made in distilled water, which is not at all surprising considering the 
known injurious effects of fresh water on marine organisms and their 
sexual products. 
Pieri admits that his experiments would be more convincing if a 
centrifugal machine and a porcelain filter had been employed in mak- 
ing the extract. He believes, however, the fact to be established that 
an extract of spermatozoa contains a chemical substance capable of 
causing the development of unfertilized eggs of the species producing 
the sperm. ‘This substance he believes to be a soluble ferment, 
ovulase (Dubois, 1900, Mémoires Soc. Biol. Paris, 52, p. 197). No 
evidence is offered in support of this view. 
Winkler’s experiments and results are similar, though slightly dif- 
ferent methods were employed by him to obtain the extract, and 
greater precautions were taken to exclude from it living spermatozoa. 
Sperm of Spherechinus granularis or Arbacia pustulata was put into 
distilled water, shaken frequently during half an hour, and the fluid 
then filtered five or six times through three thicknesses of filter paper. 
The fluid was then brought up to the density of sea water by adding 
to it salt obtained by evaporation of sea water. 
Sperm extract was also prepared by putting sperm into concen- 
trated sea water (400 c.c. evaporated to roo c.c.). In this sperma- 
tozoa shrunk at once, but were allowed to stand for half an hour, 
being frequently shaken. The extract was filtered as already 
described and then diluted to the concentration of normal sea 
water. 
In the extract obtained by either method a certain number of 
unfertilized eggs underwent cleavage, though the process was not of 
the normal sort, and it did not progress beyond the 4-cell stage. 
Stained eggs showed that genuine mitoses occurred. Control lots 
which were put into sea water, instead of sperm extracts of the same 
density, did not develop in any instance.. 
Only negative results were obtained by heating sperm to 50°-60° C. 
in sea water and placing eggs in the cooled fluid. Winkler expresses 
no opinion as to the chemical nature of the extract substance which 
causes the development of unfertilized eggs, but thinks the idea of 
