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, afford 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. Fluid 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. Set K. March 14, 1849. Atmosphere 55- 5 FAHR. Water 

 55 FAHR. 



No. 1. A single drop of the Jittered fluid was 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 Jiltered, 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 of Jiltered fluid were added to one ounce of water with sixty ova, 

 but not one egg became impregnated. 



No. 4. Three drops ofjilteredfluid were added to one ounce of water with one hun- 

 dred and jive 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 flltered, 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 daysjifteen embryos had been produced from these ova. 



* Journal de 1'Institut, 1840, No. 362, p. 908. 



