ALG^. 131 



autumn, are very similar to the ordinary neuter cells, 

 only they are more numerous. The contents assume 

 a dark green colour, at first having a frothy appear- 

 ance from the formation of vacuoles, but ultimately 

 become packed with protoplasm, but never undergo 

 any process of subdivision. They acquire a flask- 

 shape, with the narrow end to the circumference of 

 the sphere. When ready for impregnation a spherical 

 form is assumed, enveloped in a gelatinous membrane. 

 The male cells at first more resemble the neuter 

 cells, and when they have attained definite dimensions 

 they begin to divide ; but they are of a lighter colour 

 through containing less chlorophyl. They are ulti- 

 mately resolved into a bundle of cells, each consist- 

 ing of an elongated body, in which the green colour 

 becomes reddish yellow, with a long and colourless 

 beak, furnished at its base with two long movable 

 hairs, and possessing also an eye-spot. The whole 

 antheridium is enclosed within a gelatinous envelope, 

 each of the contained bodies being a spermatozoid. 

 These are fully developed just at the time that the 

 oogonia, or female cells, are matured. By the breaking 

 up of the antheridium the enclosed spermatozoids 

 are set free and float actively within the gelatinous 

 envelope, through which they speedily find their way 

 into the cavity of the parent sphere. When entirely 

 free they soon cluster around the female cells, or 

 oogonia, and some of them penetrate the gelatinous 

 envelope, and coalesce with the contents of the 

 oogonium, which now becomes fertilized and secretes 

 a new cell wall. This is at first smooth but after- 

 wards covered with conical prominences, which gives 



