AND ON THE DIRECT AGENCY OF THE SPERMATOZOON. 249 



April 2, 185 1 . Atmosphere 55. Ten eggs were passed into a large glass cell, and 

 each egg was touched once only with the pin point dipped lightly into the fluid for each 

 egg. This experiment was perfectly successful, as the chamber was formed above 

 the yelk in four or five of these eggs, and at the end of five days three of them had 

 produced embryos. In these instances the pin had been allowed to remain in contact 

 with the egg, and the fluid to drain off it for one or two seconds. 



Six eggs were also placed in another cell and each was touched with the loaded 

 pin point when the fluid employed had been obtained about a quarter of an hour. 

 Two of these eggs became partially fecundated, as shown in the formation of the 

 respiratory chamber. In each of these the yelk became slightly elongated, a symptom 

 which always precedes the first cleavage ; yet they did not undergo further alteration, 

 but with the remaining four were abortive. 



Twenty-three eggs were included in a large cell as a further experiment, and each 

 egg was touched once with the pin-point loaded each time, when the fluid employed 

 had been one hour and three quarters mixed with water. Four of these also had the 

 chamber formed, and segmentation commenced in them, at the end of four hours 

 and a half; but the majority were only partially fecundated, as only one of the 

 twenty-three eggs produced an embryo. The fact of this production, however, shows, 

 that an exceedingly small amount of influence, even at a long period after the fecun- 

 datory fluid has been removed from the body in which it is generated, is sometimes 

 sufficient to occasion the development of an animated being ; and that although a 

 plurality of spermatozoa, supplied to the egg, appears always to be necessary to 

 ensure fecundation, yet that the result seems to depend less upon the abolute given 

 number, or numerical relation of these bodies, to the egg, than on the measure of 

 vitality possessed by those which are brought into actual encounter with it, as a very 

 small number appears to be more efficient when employed immediately after their 

 removal from the body, than a much larger number after a prolonged interval. 



(b.) Pin-head application of fluid. The preceding experiments having been made 

 with the smallest quantity of fluid, and consequently with the fewest spermatozoa 

 that could be applied directly to the egg, it was desirable to increase the number of 

 these bodies without applying them in excess, and for this purpose the head of a very 

 small pin, the smallest size used by insect-collectors, was employed, instead of the 

 point of a larger sized pin. An endeavour was also made, as in the previous trials, 

 to ascertain the number of spermatozoa which the head of this sized pin, dipped 

 lightly into fluid, was likely to be the means of conveying to the egg. It was then 

 found that the loaded pin-head deposited on a plate of glass, in the minute quantity 

 of fluid which adhered to it, from at least fifty to one hundred and fifty spermatozoa ; 

 a number which was not only fully sufficient to fecundate each egg to which the pin- 

 head was applied, but also other eggs which might happen to come into contact with 

 these in the same cell and water in which the experiment was made. 



Six eggs, placed in a single cell, were each touched once only with the pin-head, 



