60 FECUNDATION 



found considerably advanced along the Fallopian tube in animals killed 

 immediately after or even before sexual union, not only proves the spon- 

 taneous maturation and discharge of ova from the ovary, but also renders 

 highly probable the opinion, that not merely at the ovary, but at any part 

 of the tract from this organ to the uterus at which the ovum first comes 

 in contact with the seminal fluid, fecundation of it may be there effected. 

 Bischoff* is of opinion that the ovum may sometimes be fecundated at 

 the ovary, but that most commonly it escapes from this organ previous to 

 the arrival at it of the seminal fluid, and that fecundation is then effected 

 in the Fallopian tube. He considers that by the time the ovum reaches 

 the uterus, or even the lower end of the Fallopian tube, its capacity for 

 being impregnated is lost. His reasons for this supposition, are founded 

 on the changes indicative of impregnation observed in the yolk of the 

 ovum previous to its entrance into the uterus, and on the complete 

 cessation of the sexual desire in those animals in which, after death, he 

 found that the ova had passed into the uterus, or had arrived at the lower 

 part of the Fallopian tube. Pouchet,| on the other hand, maintains that it 

 is only in the uterus or the lowest part of the Fallopian tube, that fecun- 

 dation takes place, for, according to his statement, the seminal fluid never 

 penetrates so far as the ovary, and seldom, if ever, extends beyond the 

 middle of the Fallopian tube. He believes that Bischoff and Wagner 

 must have mistaken for spermatozoids on the ovary a form of Entozoa, 

 which he describes under the name of Pseudo-zoospermes.J 



No confirmation has been afforded to the opinion entertained by Pre- 

 vost, and Dumas, and by Dr. Barry, that the spermatozoids enter bodily 

 into the ovum, and as believed by the first-named observers, constitute the 

 embryo. Neither has any other en.bryologist succeeded in finding any 

 opening or fissure in the zona pellucida, through which the spermatozoids 

 might be enabled to enter the ovum, as was described by Dr. Barry : || 

 Bischoff, who has repeatedly but fruitlessly made search for such an open- 

 ing in the ova of bitches and rabbits, disbelieves entirely in its existence. *[[ 



Fecundation in Plants. In his enquiry into the question concerning the 

 probable mode in which fecundation of the ovum of animals is effected, 

 Professor Miiller was led into an examination of the several theories 

 adopted in explanation of the process of fecundation among plants ; espe- 

 cially of those of Schleiden and Meyen. Since then, the opinion enter- 

 tained by Schleiden that the extremity of the pollen-tube pushing the 



* Entwickl. des Hunde-Eies, p. 30. 



t De la Fecondation, p. 35, et seq. ; de 1'Evolution Spontan. p. 370. 



% Del'Evol. Spont.p.416. 



Philosophical Transactions, 1840, p. 533; and 1843, p. 33. In the latter place Dr. 

 Barry states that he has twice distinctly observed several spermatozoids within the zona 

 pellucida of ova from the rabbit. || Miiller's Physiology, p. 1497, and fig. 166 D. 



TI Eutwickelungs-gesch. des Hunde-eies. p. 17. 



