Dr. Alex. Brown — On Solenopora. 



201 



(&.) Size of the cells of Solenopora. 

 It may be objected that since the cells of Solenopora are so 

 much larger thaa those of a Nullipore, the genus Solenopora can 

 hardly be compared with the recent calcareous Algte. A comparison 

 between the cells of various genera of the Corallinese and the cells 

 of the genus Solenopora, will dispel all such objections. A glance 

 at Fig. 13 shows the marked variations in the size of the cells 

 ofa repent Nullipore (A), of Amphiroa exilis (B), of Solenopora 

 filiformis (C), and of Solenopora Jurassica (D), all being drawn to 

 the same scale. 



M 



c 



Fig. 13.— a Cells of a recent Nullipore {Lithothamnion) . x 160 d. 



B Cells of Amphiroa exilis. x 160 d. (modified after Solms-Laubach). 

 C Cells of Solenopora filiformis, Nich. x 160 d. 

 D Cells of Solenopora Jurassica, Nich. x 160 d. 



Such au illustration at once clears up any difficulty on the above 

 point, for there appear to exist all gradations of size of the 

 tissue-cells. 



(c.) Beproductive organs. 



Evidence in regard to these is not yet so complete as one would 

 wish ; still, examination of some specimens clearly shows traces of 

 structures that can be accounted for in no other way than by 

 regarding them as the remains of reproductive organs. 



Ihus, a specimen of Solenopora compacta, var. Trentonensis, on 

 examination of a tangential section, is seen to possess two distinct 

 kinds of cells, as mentioned above in the description of this species. 

 The larger cells here (Fig. 2) are sporangia, and can be compared 

 with the sporangia of Melobesia deformans (Fig. 12), where they 

 exist as large cells among the ordinary tissue-cells of the thallus. 



Again, a tangential section of a specimen of Solenopora Jurassica, 

 shows certain spaces amongst the general cellular mass. These 

 spaces are oval or circular in form, and in one specimen from 

 Malton, Yorkshire, are arranged in a concentric row. The latter 



