M 



FIG. 2. 



The development of isopores and heterospores in Thalassicolla nudeata. (After Brandt, 1005.) 

 A-C, isospore-fonnation, x 100. The large nucleus (N) breaking up into spore nuclei (N. Isp). 

 D, an isospore (x 2000) ; Cone, stratified concretions lying in proteid vacuoles. E-K, hetero- 

 spore - formation, x 100. E, nuclear membrane collapsing. Nuclear figure and one intra- 

 nuclear centrosome. F, diffusion of nucleoplasm (Nm) outwards. G, organisation of second- 

 ary nuclei (N.>). H and K, segregation of these nuclei to form heterospore nuclei. L, mega- 

 spores. This figure shows the two flagella arranged like those of a Dinoflagellate. M, micro- 

 spores. L, M, x 1000. 



101 



