130 



A. OKA. 



complete. Nitsche'.s statement that the cells evacuate the caskets 

 before their closure is probably an error. 



As already said, the inner cystogenous layer thins out by the 

 flattening of its cells, and when the chitinous plates completely 

 inclose the granular mass it forms a thin epithelial covering to the 

 latter directly within the central capsule (figs. 42-46, PI. XIX, Enü. 

 m.'). The size of the nuclei becomes smaller as the height of cells 

 decreases, and reaches at last the dimensions given before wdien 

 the niatiu-e statoblast w-as described. The cells of this membrane are 

 distinctly bounded and hexagonal in sha})e. 



Keturning to the stage represented in fig. 41, the granular 

 spheres, composing the mass contained within the cystogenous cup, 

 have each a centrally placed nucleus, and growing larger (fig, 42, 

 PI. XIX.) press upon one another so that they assume a polyhedral 

 form. P'lie}- remain distinctly bounded as long as the rim of the 

 chitinous cup remains open, but fuse together after the latter closes. 

 It is a singular fact, that in some statoblasts, either the granular 

 mass is produced in over-quantity, or the capsule formed is too small, 

 so that a portion of the mass is left outside the statoblast as the cap- 

 sule closes, afterwards disappearing. 



The nuclei of the granular mass become smaller as the develop- 

 ment of the statoblast advances. Arrived at a stage represented in 

 tig. 42, PI. XIX, the nuclei almost lose their peculiar chromatin reac- 

 tion, and stain very faintly, so that in some preparations it is very 

 ditiicidt to detect them. This condition, however, lasts for a very 

 short interval, and in all the later stages the nuclei are again distinct- 

 ly visible. This [)eculiar behavior of the nuclei may have lead 

 Verworn to assume that the granules are the product of the splitting 

 of nuclei and that the latter as such are not found after the com- 

 plete development of the granules. 



