900 OF GENERATION ACTION OF THE FEMALE. 



( 747), and in the changes which occur as the immediate consequence of 

 that contact, that the act of Fecundation essentially consists. The most re- 

 cent observations of the late Mr. Newport upon the process of impregnation 

 of the Frog (some of which the Author, through the kindness of Mr. Newport, 

 had the opportunity of verifying) showed that the spermatozoa become im- 

 bedded in the gelatinous envelope of the ovum, within a few seconds after 

 they come into contact with it; and that they then absolutely pass through 

 the vitelliue membrane, into the interior of the Ovum, 1 where they probably 

 undergo a gradual diffluence ; and thus the product of the "sperm-cell" 

 may be absorbed into the "germ-cell," and may intermingle with its con- 

 tents, the Spermatozoon being nothing else than an embodiment of the 

 fertilizing material developed within the sperm-cell, which is endowed with 

 a temporary power of movement in order that it may find its way to the 

 Ovum. In the Osseous Fishes it has been shown by Dr. Ransome that the 

 Spermatozoa pass through a minute opening in the external membrane of 

 the ova, termed the micropyle. A similar opening has been observed by 

 Muller and others in Insects, Acephalous Mollusks, and in several Echino- 

 dermata ; and its use, as Dr. Allen Thomson has suggested, is probably to 

 facilitate the fecundation of ova possessed of very thick external coverings. 

 A micropyle has not been seen in any of the Mammalia, though the point 

 has been closely investigated by Reichert in the Guinea-pig. It has been 

 remarked by Mr. Newport, that Spermatozoa whose spontaneous motility 

 has ceased, no longer possess the fecundating power ; and this fact concurs 

 with other phenomena to indicate, that it is not only a certain material, but 

 a vital force of which that material is (so to speak) the vehicle, which is re- 

 quired to effect this most important operation. 



749. The precise share which the Germinal Vesicle performs in the 

 changes which take place in the ovum about the period of fecundation, 

 has not yet been satisfactorily determined. According to Dr. Barry (loc. 

 cit.), the germinal vesicle becomes filled with a new development of cells, 

 which sprout, as it were, from its nucleus (the germinal spot) ; and after 

 fecundation, a pair of cells is seen in the space previously occupied by the 

 pellucid centre of the nucleus, which is developed at the expense of the 

 rest, and is the true foundation of the embryonic structure. This view is 

 to a certain extent confirmed by the observations of Wagner on the ova 

 both of Frogs and Mammalia, and by those of Vogt on those of the liana 

 obstetricans ; both of which lead to the belief that such a process of cell- 

 formation does take place within the germinal vesicle, but that, instead of 

 the further development being carried on within the germinal vesicle, as 



1 Philos. Transact, 1853, pp. 266-281. Prof. Bischoff, the hig-hest authority on 

 this subject, who had disputed the validity of all previous observations on the pene- 

 tration 'of the spermatozoa into the interior of the Ovum, fully confirmed those of 



the majority of cases, the act of fecundation occurs whilst the ovum is traversing the 

 Fajlopian tube. According to Coste, the duration of the passage of the egg through 

 the oviduct of the fowl varies fn.m four to six hours, and of its retention in the cloaca 

 four hours. The influence of a single act of coition in the fowl, according to the same 

 observer, may extend to from five; to six eggs, which may he laid during the eleven 

 to seventeen subsequent days. Harvey extended the influence even to twenty eggs. 

 His agrees with Uoste, and observes, that in all probability these eggs were impreg- 

 nated at different periods ; and hence some of the variations in point of development 

 of the cicatricula may proceed. His has also observed that the eggs of fowl, laid in 

 the middle of summer, are more advanced, and develop with greater rapidity than 

 those laid towards the end of autumn. 



