FECUNDATION. 353 



in some instances, perfectly-formed spermatozoids in the very- 

 substance of the vitellus. 1 



The following very interesting experiment by Lott has a 

 certain amount of bearing upon the question of the penetra- 

 tion of spermatozoids through the vitelline membrane. Lott 

 made a little bag of the caecum of the sheep, moistened the 

 membrane with a weak saline solution, introduced ten to 

 twelve drops of ejaculated semen, and, having closed the bag 

 securely, placed it in a vessel containing the same saline solu- 

 tion. In ten minutes, he drew out the bag and found, in the 

 exterior liquid, a number of motionless spermatozoids. This 

 observation he often repeated, with similar results ; showing 

 that the spermatozoids had actually passed through this deli- 

 cate animal membrane.* How far this explains the passage 

 of spermatozoids through the vitelline membrane, it is diffi- 

 cult to say ; but the results are certainly curious and some- 

 what startling. 



All direct observations on the lower orders of animals 

 have shown that several spermatozoids are necessary for the 

 fecundation of a single ovum ; but we have no definite idea 

 of the number required in mammals, much less in the human 

 subject. Nor do we know what becomes of the spermato- 

 zoids after they have come in contact with the vitellus. All 

 that we can say upon this point is, that there is probably a 

 molecular union between the two generative elements, soon 

 to be followed by the remarkable series of changes involved 

 in the first processes of development. 



1 WEIL, Beitrage zur Kentniss der Befruchtung und Entwicklung des Kanin- 

 chendes. Mcdizinische Jahrbucher, Wien, 1873, S. 18, et seq. 



2 LOTT, Zur Anatomic und Physiologic des Cervix Uteri, Erlangen, 1872, S. 

 140. 



