40 THE AMPHIOXUS. 



The eggs ejected were surrounded by numberless 

 spermatozoa, which turned like radii towards the 

 membrane of the egg, held fast to it by their heads 

 and tried to make their way into it. 



At the same time the vitelline membrane began to 

 separate rapidly from the protoplasm of the egg, 

 probably under the influence of the sea water. It was 

 only at one point that the membrane adhered any 

 longer to the protoplasm, it having there in conse- 

 quence the appearance of being drawn in like a funnel. 

 I think that this is just the place in which a sperma- 

 tozoon made its way into the egg. This place I 

 regularly found near to the lower pole. 



The separation of the vitelline membrane advances 

 with great rapidity, and it expands to many times 

 the diameter of the egg, enclosing a clear liquid, which 

 can certainly be nothing else than diffused sea-water. 

 This expansion of the vitelline membrane advances 

 also further during the first segmentation stages, and 

 reaches such a degree as may be seen in Fig. 1, where a 

 later embryo stage is formed within the egg membrane. 



These conditions exhibit to us already the remarkable 

 and extreme elasticity of the vitelline membrane. I will 

 introduce here some further observations, which give 



