MATURATION AND FECUNDATION OF THE OVUM. 109 
considerable size (average 25 cm. in length), found in large 
numbers in the intestines of horses. It can easily be obtained, 
especially in winter (at Liege), in the living condition in any 
numbers required. The preparation of its ova is effected with 
great ease : its spermatozoa are large, non-motile, and conspi- 
cuous; lastly, from a single female a large number of ova in 
each successive stage can be obtained, from those still in the 
ovary to those which have begun to segment. In order to 
expose the sexual organs all that is needed is to slit the animal 
longitudinally with scissors. The maturation and fecundation 
of the ovum take place during its slow passage down the oviduct 
and uterus, the latter of which contains large numbers of 
spermatozoa. A given stage of development occurs at a 
certain position in the sexual tube, so that by taking a small 
portion of the tube thousands of eggs are obtained all in the 
same stage. The uterus is fifteen to twenty cm. in length, and 
the ova come into contact with the spermatozoa at its upper 
end. With regard to the penetration of the male element 
the author remarks, ‘ II est facile de demontrer en cinque 
minutes, non pas seulement a des histologistes experimentes, 
mais au dernier des profanes, la penetration du zoosperme. 
Methods. — 1. By examining the eggs fresh, either in 
Kronecker’s artificial serum (distilled water 100, NaCl 6, 
HNaO '06j or in the liquid of the body of the Ascaris, all the 
phases of the penetration of the spermatozoon can be made 
out : in the oldest ova the various membranes, the two polar 
globules, and the pronuclei can be seen, but the details of the 
changes cannot be made out in fresh eggs. 
2. One of the methods which gave the best permanent pre- 
parations was to kill the ova with nitric acid 3 per cent., 
leave them in this for one hour, then wash with water, place 
one or two hours in alcohol 33 per cent., then transfer to 
alcohol 70 per cent. For younger ova it is necessary to open 
the uterus and prepare the ova on the slide ; for the ova at the 
inferior end of the uterus this is not necessary. For staining 
after the use of nitric acid, borax carmine, fuchsine, and 
methyl green gave the best results. 
