REPRODUCTION 



179 



first contains several nuclei of which all but one subse- 

 quently retreat into the main filament again before the 

 septation is completed. 



The oogonium eventually forms a rounded mass with a 

 truncated conical projection of clear protoplasm on one 

 side where it opens. The antheridium which is multi- 

 nuclear and more or less coiled or like a hook is 

 open at the tip. Its contents first break up into swarm- 



PIG. 75. A, Conjugation of Spirogyra guinina. B, Spirogyra longata; z, 

 zygospore. C, cell of Spirogyra jugalis; k, nucleus; ch, chroma tophores; p, 

 pyrenoid. (Strasburger, Noll, Schenck, and Karsten.) 



ing spermatozoids which it then discharges together with 

 its mucilaginous contents. The spermatozoids are very 

 small, each being provided with a single nucleus and two 

 cilia. They collect about the oogonium into which one 

 of them eventually penetrates to fertilize it by the fusion 

 of their nuclei. The oogonium then becomes converted 

 into a resting oospore which eventually germinates with 

 the production of a filamentous thallus. Here we find a 



