204 
MR. NEWPORT ON THE IMPREGNATION OF 
the spermatozoa, by filtration from the fluid in which they move, and testing the ova 
with these and the fluid separately, affbrd good proof of the agency of these bodies ; 
while immersion of the ova in coloured fluids, at the moment of their passage from 
the body of the frog, seems equally fitted to ascertain the believed existence of a 
fissure or perforation through the envelopes during their expansion. The experiment 
of filtration was originally performed by Prevost and Dumas with well-marked re- 
sults, and it has since been repeated by the first of these observers* by a different mode, 
— endosmose through the operation of galvanic currents. The mode pursued by my- 
self was that originally adopted by these observers : — careful mechanical filtration, by 
simply passing the fluid portion of diluted semen through folds of filtering-paper. The 
paper I have employed, and which alone was fitted for the purpose, was the best 
Swedish filtering-paper employed by chemists in their most delicate analyses. A large 
proportion of the spermatozoa were always retained, even on a single filter, although 
a few usually passed through ; but this, as the results show, was not in reality a dis- 
advantage, when a few only were present in the filtered portion. When three or four 
folds of filtering-paper were employed, the whole of the spermatozoa were removed. 
Filtration of Seminal Fluid.— ¥\\x\d obtained from a male frog, immediately after 
removal from the female, was mixed with about twice its quantity of water and placed 
on the filter. Portions of this fluid as they passed through were repeatedly examined 
with the microscope. Some of these filtered specimens contained a very few sperma- 
tozoa, usually not more than three or four in the drop examined, but sufficient 
occasionally, as the results proved, to effect impregnation. 
Filtration Experiments. — K. March 14, 1849. Atmosphere 55°'5 Fahr. Water 
55° Fahr. 
No. 1. A single drop of the filtered fluid added to one ounce of water, in which 
forty-six ova were immersed. Not a single egg became segmented or produced an 
embryo. 
No. 2. A single drop of the diluted fluid, not filtered, but two hours after it had 
been obtained, was added to one ounce of water with ninety ova. Not a single egg 
was segmented or produced an embryo. 
No. 3. Two drops oi filtered fluid were added to one ounce of water with sixty ova, 
but not one egg became impregnated. 
No. 4. Three drops of filtered fluid were added to one ounce of water with one hun- 
dred and five ova. Two of these were partially impregnated, as shown by their be- 
coming imperfectly segmented (Plate XIV. fig. 11 and 12), but neither of them pro- 
duced an embryo. 
No. 5. Three drops of diluted fluid, not filtered, but two hours after being mixed 
with water, were added to one ounce of water with seventy-six ova. Several of these 
became segmented, but more tardily than in the following experiment. No. 7- At the 
end of seventeen days fifteen embryos had been produced from these ova. 
* Journal de I’lnstitut, 1840, No. 362, p. 908. 
