Dr. Alex. Brown — On Solenopora. 



199 



of cells is excellently seen (Fig. 11). The cells are fairly large, 

 and occupy the whole space between each dark concentric line. 



f ^^ ^ 



Fig. 11. — Long. sect, of thallus of Amphiroa exilis. x 160 d. (modified after 

 Solms-Laubach). 



In another form, Melobesia deformans, it is necessary to note the 

 arrangement of the spore-bearing cells (sporangia) in relation to 

 the tissue-cells of the thallus. The illustration in Fig. 12 will 

 clearly show this, where the larger cells are tetraspore-producing 

 cells, and the smaller the ordinary tissue-cells of the thallus. 



f9 



M2 



Fig. 12. — Surface view of the tliallus of Melobesia deformans, sliowing tetrasporangia. 

 X 450 d. (after Solms-Laubach). 



Let us now examine the points wherein the ancient form Solenopora 

 resembles members of the group of calcareous Algse. 



(a.) Structure, Growth, and Arrangement of tissue-cells. 



In existing forms of Corallinece the concentric arrangement of 

 cells, though very general, is not always observed. As regards 



