974 



tration of the spermatozoon bodily into the ovum. All the observa- 

 tions he has been able to make on the ovum of the Frog, both mi- 

 croscopically and experimentally, are opposed to the belief that any 

 fissure or perforation exists in the envelopes of the ovum, as de- 

 scribed by Dr. Barry in the ovum of the Rabbit, and through which 

 the spermatozoon was supposed to enter. Neither is he able to con- 

 firm the statements of Prevost and Dumas, that the spermatozoa 

 penetrate into the substance of the envelope of the egg either of the 

 Frog or the Newt; and he thinks these distinguished observers 

 must have supposed that spermatozoa which they saw on the ex- 

 terior of the ovum were in the interior. The author has put this 

 question to the test in the ovum of the Newt, Lissotriton punctatus. 

 He extracted an ovum, which he had reason to believe had not been 

 impregnated, from the oviduct, and placed it with seminal fluid in 

 water, and immediately afterwards examined it with the microscope. 

 Spermatozoa were detected upon it in less than one minute after 

 immersion; but neither then, nor at any subsequent period, could 

 even a single spermatozoon be seen within it, although the whole 

 Interior of the egg was brought within focus of the microscope, and 

 distinctly recognised. This egg was preserved in a small glass cap- 

 sule beneath the microscope, and watched until the embryo was 

 produced. Spermatozoa were recognised on the exterior during 

 the first forty-eight hours. 



But although spermatozoa do not enter the interior, they are in- 

 variably found in contact with the surface of the impregnated ovum, 

 and this contact is essential to their agency. The author also shows 

 that the envelopes of the ovum are essential to its fecundation, and 

 that ova taken from the ovary, or from the cavity of the body after 

 they have left the ovary, but have not yet entered the oviduct and 

 acquired their gelatinous coverings, are not susceptible of being im- 

 pregnated. The coverings imbibe water by endosmose, but do not 

 usually admit solid particles of matter equal in size to spermatozoa 

 into their texture, as was proved by immersion in (solution of carmine. 



The author then enters at length on an examination of the agency 

 of the spermatozoa as affected by chemical media. Availing him- 

 self of a fact ascertained during a chemical analysis of seminal fluid 

 by Dr. Frerichs, that the spermatozoa are decomposed by caustic 

 potash, he conceived the possibility of so employing this agent as to 

 render it a test in experiment. Ova were passed from the body of 

 a frog on a dry surface, without being in contact with water, until 

 seminal fluid mixed with it was applied to them. After the lapse 

 of a given time, solution of caustic potash, of sufficient strength to 

 decompose the spermatozoa immediately, was also applied, and as 

 quickly as possible afterwards was again diluted and removed with 

 water, before the potash, as found by other experiments, acted pre- 

 judicially on the ova. The result was that segmentation of the yelk 

 usually took place even when the interval of time between the ap- 

 plication of the seminal fluid and the solution of potash was only 

 one or two seconds, but no embryos were produced. When, how- 

 ever, the interval was five seconds, a very few embryos were formed ; 



