346 WILSON. [Vol. IX. 



There are two or three flagellated chambers present in this 

 sponge, one of which is shown in the figure, f. c, but I can 

 communicate nothing as to the details of their formation, 

 except that they are independent of one another and surrounded 

 by a solid mass of cells. 



IV. Early Stages in Egg Development of Hircinia 



ACUTA. 



The "Loggerhead" sponge, Hircinia acuta, is very abun- 

 dant in the shallow water round Green Turtle Cay, forming 

 circular masses often of very large size, which contain great 

 numbers of annelids, Alpheus, and other semi-parasitic forms. 

 It is with eggs in this locality during September, and probably 

 for a much longer period. My observations on this form are 

 very few, dealing only with the development of the ovarian 

 egg and the segmentation. 



The mesoderm of Hircinia has in many regions a cartilagi- 

 nous appearance, consisting of a clear non-stainable matri.x 

 containing cavities in which lie the cells. When the cell 

 shrinks away from the wall of the cavity, the latter comes 

 plainly into view, PL XXIII, Fig. 114 (bit of the mesoderm). 

 Tracts of this sort are often found in which flagellated cham- 

 bers are absent, and in such places egg cells frequently occur. 

 In Fig. 114 is shown an egg cell {0. ov.) about twice the size 

 of the surrounding mesoderm cells, and containing a large 

 nucleus with a single nucleolus. The egg is enclosed by an 

 incomplete follicle, composed of neighboring mesoderm cells 

 which apply themselves closely to the wall of the egg cavity. 

 During its increase in size the egg becomes stored with yolk, 

 and its nucleus undergoes changes similar to those described 

 for Tedanione. 



To the few mesoderm cells enclosing the young tgg, others 

 are gradually added, and in this way a complete follicle is 

 formed, PI. XXIII, Figs. 115, 115', consisting of a single layer 

 of cells. In Tedanione the follicular cells very early flatten out 

 into a thin membrane, but in Hircinia this change does not 

 take place until after the beginning of segmentation. In 



