No. 3-] DEVELOPMENT OF MARINE SPONGES. 341 



find any more, my conclusion is that these anchors are foreign 

 particles, and that bits of the sponge to which they originally 

 belonged entered Tedanione and were used as food. 



2. Development. 



My observations on the development of Tedanione and Hir- 

 cinia deal only with the egg development, going in the former 

 sponge as far as the formation of the swimming larva, but in 

 the latter no farther than the segmentation. 



Tedanione was with eggs in September and October and 

 possibly for a much longer time at Green Turtle Cay, Bahamas. 

 Adults were kept in aquaria, and after an hour or two, as a 

 rule, a few ciliated larvae were thrown out of the oscula. 



The very young ovarian egg is of an irregular shape and lies 

 in the mesoderm surrounded by a follicle of flattened cells, 

 PI. XXIII, Fig. 102, ov. 0. It has a large nucleus and single 

 nucleolus. As the egg increases in size it becomes rounded, 

 its protoplasm becomes filled with yolk, and the nucleus 

 undergoes certain changes, which are not completed until the 

 egg has attained its full size and is ready for segmentation. 

 A general idea of the change in size and character of the egg 

 during its growth may be gathered from a comparison of PL 

 XXIII, Figs. 102, 103, 104, 105, 106, drawn to the same scale 

 and representing successive stages in the life of the egg. 



During the increase in the size of the egg, its follicle is 

 constantly surrounded by a dense mass of mesoderm cells, as 

 may be seen in the section, Fig. 103 (w^cj. ^the cells in ques- 

 tion; the egg is one-half the full size). These cells have large, 

 plump bodies which stain well, being full of a finely granular 

 yolk. The shape and direction of the cells on the outskirts of 

 the mass indicate a migration of mesoderm cells from all 

 quarters to the egg. By the time the egg has reached its full 

 size the surrounding mass of cells has dwindled away to a 

 small number. Fig. 104, and during the remaining period of 

 its life in the parent sponge the embryo is surrounded by 

 ordinary mesoderm, in which the cells are not more thickly 

 crowded than elsewhere in the body. It is only while the egg 



