73 



(fig. 143), and t}ie spores round off, becojning oval in 

 shape. The lowest sjore, up to tliis time attached to the 

 stalk cell hy a slender t}iread of cytoplasm, hreaJcs away 

 at the point of attacliment, and the strand is v/ithdra\vri 

 into tiie "body of tlie spore. The gelatinized cell wall, nov/ 

 very much sv/ollen, appebjr*s to dissolve in the sea v/ater, 

 and tlie four spores are set free, aLmost iimnedij-.tely "be- 

 coming spherical. Like tiie carpospores, they are heavier 

 th.an sea-vvater, and slowly sink, if left undisturhed , 



The ras,ture tetraspore resembles the ca.rpospore in ap- 

 pearance. It is approximately spherical. In the centre 

 the large nucleus is conspicuous, v.ith its ch-romatin seg- 

 regated into 12-20 small masses. Immediatelj'^ around tlie 

 nucleus is a zone of rather dense cytoplasm; outside this 

 the cytoplasm is coa,rsely vacuolar. In the perijiheral cy- 

 toplasm is a single layer of chroma.tophores, outside which 

 is the limiting membra.ne of t}ie spore. Fo cellulose cell 

 wall is visible. 



The average size of tlie tetrasporic structures is 

 sliovm in the follo-vdng table: 



