AND ON THE DIRECT AGENCY OF THE SPERMATOZOON. 255 



to the circumstance of the fluid being too thick ; but as we shall presently find, this, 

 perhaps, may admit of a different interpretation. 



My first object having been to learn how small a number of spermatozoa is suffi- 

 cient to fecundate an egg, it may well be supposed that the facts just mentioned 

 were exceedingly puzzling, and they were rendered still more so by the circumstance 

 that a different result occurred with three other eggs from the same frog, employed 

 at the same time as those in the preceding experiments. Two of these eggs, placed 

 like the others, each in a separate cell, in a mixture of one part of seminal fluid to 

 six parts of water, two hours and twenty minutes after the fluid had been obtained, 

 became fecundated. In each of these the chamber was formed above the yelk, 

 segmentation took place, and proceeded regularly, and each egg subsequently pro- 

 duced an embryo. In the third egg the chamber was formed, but the yelk became 

 irregular in outline, and did not undergo segmentation. It had merely three parallel 

 depressions on its upper surface, after which it became strangely altered in form, and 

 was abortive. The cause of this failure seemed to be the same as in the preceding 

 experiments, an excess of spermatozoa in encounter with the egg, as subsequent ex- 

 periments tended to show. 



Seven eggs were passed into one large cell, and one egg into each of two separate 

 cells, and the cells were then filled with a mixture of fluid and water, which was so 

 dense as to appear turbid and opaline. This appearance was in part due to the fluid 

 containing a large proportion of developmental cells. The result in each instance 

 was very marked. The fluid at the time it was employed had been mixed with water 

 about one hour and jive minutes, and the temperature at the time the experiment was 

 made was 56 FAHR., but the eggs were soon afterwards removed to a temperature of 

 62 FAHR. At the end of Jive hours the yelks of two of the eggs had become partially 

 segmented, but the changes were continued only in one. The remaining eggs had 

 been more injuriously affected. Their yelks had become shrivelled and contracted, 

 and resembled withered apples. In this experiment it was evident that the effect had 

 been occasioned by an excess of impregnating influence, but in what way it was not 

 then easy to understand. The yelks of these eggs looked very like those of eggs 

 which had been in contact with solution of potass, or of those to which stale and de- 

 composing fluid had been supplied. 



But it was possible that this change of form might be due to some injury sustained 

 by the eggs in their removal from the body of the frog, or to some accidental cause 

 in their removal to the cells, before fecundation. In order, therefore, to remove all 

 doubt in this respect, another trial was made with two other eggs, which were so 

 carefully passed into cells as to avoid all suspicion of injury to them, and the cells 

 were then filled with mixed fluid like the preceding. The yelks of each of these eggs 

 also changed their form, and one of them became irregularly contracted and pear- 

 shaped. Of the whole of the eggs employed in these experiments only one underwent 

 segmentation, and produced an embryo. The others were not fecundated. It was 



