120 ERNEST WAKREN. 



on the walls of the expanding- cavities (text-fig. 6, a, b). 

 In fig. H the pigment-degeneration is seen proceeding in the 

 inner portion of two contiguous endoderm cells. 



(4) Sertularella meditorranea Hartl. 

 Text-fig. 7. 



This common species on the Natal coast exhibits a type of 

 pigment- degeneration which differs considerably from the 

 kinds of degeneration already described. Older, exposed 

 colonies appear yellowish-green to the naked eye. Micro- 

 scopical examination shows that this condition results from 

 the presence of more or less numerous oval-shaped areas 

 which contain small yellowish granules (text-fig. 7, a, b). In 

 S. meditorranea these areas generally represent a single 

 transformed cell, or sometimes, perhaps, a portion of a cell 

 only, while in Lytocarpus f ilamentosus, Thuiaria 

 tubulif ormis, and Sertularia operculata the modified 

 areas may mostly consist of several cells. The series of 

 changes which these cells undergo are illustrated in text-fig. 7, 

 c-N. As the granules arise the general cytoplasm becomes 

 less turbid and stains less readily with ha3matoxylin (figs, c, d). 

 The nucleus undergoes change and the chromatin disappears, 

 so that the nucleoplasm becomes clear except for the nucleo- 

 lus which seems to remain unaltered for a time. Subsequently 

 even the nucleolus cannot be found and the nucleus is seen to 

 be quite homogeneous (r). The granules increase in number 

 and the cells become oval whatever the oi-iginal shape of the 

 cell (figs. e-h). The protoplasm is gradually converted into 

 yellow granules of average diameter about 0'4 ju, and into a 

 transparent matrix. 



On staining by the Kiihne-Gram method the granules 

 became reddish-yellow and the matrix a fairly dark yellowish- 

 brown. Sometimes the areas are almost perfectly spherical 

 (fig. k), and the granules may be exceedingly concentrated, 



Fig. 7. — Sertularella mediterranea Hartl. Fig, A, X 220. Fig. b, 

 X 1100. Figs, c-o, X 3000. Fig. p, x 1700. 



