226 MR. NEWPORT ON THE IMPREGNATION OF 



snake (Natrix torquata) are not affected by acetic acid, but he makes no reference to 

 its action on those of the Frog. 



4. Gum-Arabic. A thick solution of gum appears to act on the spermatozoa me- 

 chanically only, and almost immediately deprives them of motion by the obstruction it 

 opposes to them. When a minute drop of spermatic fluid is placed in the midst of 

 one of gum solution, and covered with talc, those spermatozoa which have become 

 mixed with the gum cease to move instantly, and remain with the tail and body coiled 

 in various directions ; while others at the edges and in the midst of the fluid, where 

 they are less mixed with gum, still move feebly for a few seconds, but become motion- 

 less as the gum collects around them. 



These circumstances will better enable us to understand the following experiments, 

 the object of which was to endeavour to learn how far the influence of the sperma- 

 tozoa, and the act of impregnation of the ovum partake of a chemical or of a mecha- 

 nical nature ; and also will help to determine the length of period of contact requisite 

 for impregnation. 



The following experiments bear on these inquiries : 



Potass experiments. SetP. March 25,1850. Atmosphere 48 FAHR. Water46 FAHR. 



No. 1. P.M. l h 40 m . Fifty-four ova were passed from the Frog on a dry surface, 

 and were instantly bathed with recently-obtained impregnating fluid mixed with 

 water ; and at the lapse ofjifteen seconds were washed by means of a hair-pencil 

 loaded with the solution of caustic potass before mentioned ; after which the eggs 

 were again washed freely with water. 



No. 2. P.M. l h 45. Thirty-nine ova were treated in precisely the same way, except 

 that the interval between the application of impregnating fluid and the solution of 

 potass was only Jive seconds. 



The ova were removed, after the first day, to a room in which the average tempera- 

 ture was about 60 FAHR., and at the end of the eighth day twenty-one embryos, ad- 

 vanced to near the end of the fourth period of development, had been produced in No. 1, 

 and two embryos, at a similar stage, in No. 2. This, at first thought, appeared to be an 

 extraordinary fact, seeing that the solution of potass so quickly decomposes the sper- 

 matozoa, and even renders the ovum sterile, as was afterwards found ; but, on exami- 

 nation of the details, the experiments admit of explanation -.Jirst, the seminal fluid 

 was employed immediately it was obtained, and before the application of the potass, 

 which was not used, in the first case, until after a lapse ofjifteen seconds, and in the 

 second case, of Jive seconds ; next, that in both instances the solution of potass was, as 

 quickly as possible after its application, diluted and removed by repeated washing of 

 the ova with water. Nevertheless, these experiments prove that the ovurn becomes 

 impregnated very quickly after the application of spermatozoa, and, in these cases, 

 even within the short interval oijlfteen seconds in the one, and Jive seconds in the 

 other, the difference in the number of embryos produced in the two apparently in- 

 dicating the extent in each of the deleterious effect of the solution. 



