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Scientific Proceedings (127) 



ment. An extraordinary reaction then takes place. The fila- 

 ment begins to draw back into the egg dragging the spermato- 

 zoon along with it. Not only this but all the other filaments 

 projecting from the egg are similarly withdrawn. Apparently, 

 a wave of response is started when a filament fuses with a sper- 

 matozoon. This wave must travel down the filament and over 

 the egg. 



As the filament with a spermatozoon on its tip shortens, the 

 spermatozoon is pulled deeper and deeper into the jelly and the 

 lashing of its tail becomes more and more restricted. The sper- 

 matozoon behaves like an unwilling victim and occasionally, 

 frees itself, especially when other filaments have been slightly 

 ahead in activity and have also secured spermatozoa which they 

 are now pulling in. With the microdissection needle one may 

 free a spermatozoon by breaking the filament to which it is at- 

 tached. Such a spermatozoon is generally unable to extricate 

 itself from the jelly in which it lies embedded. After a few vi- 

 brations of its tail it becomes permanently quiescent. 



By the time the filament has dragged the spermatozoon half 

 way through the jelly the base of the cone changes in shape. 

 The convexly rounded border, which gives it the appearance of 

 a rounded nipple, draws in so as to become concave. In doing 

 so it leaves the egg membrane behind and this now becomes 

 plainly visible owing to the space intervening between it and the 

 surface of the cone. By the time the filament is withdrawn so 

 as to bring the sperm head to the summit of the cone, the lifting 

 of the egg membrane has spread from the base of the cone over 

 the egg and is recognized as the fertilization membrane. 



When the filament is completely withdrawn into the base of 

 the cone the head of the spermatozoon is taken in with it. The 

 tail of the spermatozoon remains for a time outside the fertiliza- 

 tion membrane. As long as the tail maintains organic continu- 

 ity with its head it keeps up a feeble oscillatory movement. As 

 the cone recedes into the egg, the strand extending from it to 

 the tail outside the fertilization membrane breaks and the tail then 

 lies motionless. The tail can be seen for several minutes mark- 

 ing the site where the sperm head had gone in. 



