No. 2.] EMBRYOLOGY OF THE AMERICAN LOBSTER. 221 



then within, while the outer portion of the ovary represents 

 the vitellogen, as described by Herrick (86). The figure, more- 

 over, shows that the present is a secondary condition. The 

 inner blood-sinuses represent localities of invagination, and sec- 

 tions show that they occur at varying points throughout the 

 entire ovary. 



Instead, then, of having a single germogenal line, as has been 

 described in many Decapods, there are as many germogens as 

 there are deep invaginations. 



If one of the blood-sinuses is examined in detail, the lining 

 membrane (PI. XVI, Fig. io) will be found to be, in the main, 

 structureless and to contain varying numbers of blood-cells 

 (Fig. io, Cor.). At its deepest portion the membrane frequently 

 presents a pitted appearance, which under a high power seems 

 to be due to the presence of a single series of appressed cells 

 (Fig. io, //.). Connective tissue fibres stretch from the lining 

 membrane into the substance of the ovary between and sur- 

 rounding the younger developing egg-cells at the centre, but 

 losing their prominence as they approach the periphery. 



Around the more mature eggs of the periphery a distinct 

 layer of cells, the follicular epithelium (PI. XVI, Fig. io,fe.), 

 presents itself, and as we pass from the periphery towards the 

 centre these cells become less numerous and less columnar, 

 and finally, at the very centre are not distinguishable from the 

 cells that are finally to develop into eggs. 



The primitive egg-cells are arranged in bunches around the 

 distal ends of the sinus invaginations (PI. XVI, Fig. io). They 

 are more or less irregular in shape, but betray their point of 

 attachment by the direction of their major axes. A distinct 

 cell-wall is not present, and frequently two or more cells seem 

 to be in a process of fusion. 



On following the lining membrane of the blood-sinus to the 

 outside of the ovary, it is found to lead into lacunae of the mus- 

 cular layer, which, in turn, probably communicate with blood- 

 vessels. 



Passing now to the more mature ovary, the outer muscular 

 covering is found to be much thicker, though in life quite trans- 

 parent, and to exhibit the large, ripe eggs below as a surface 

 of polygonal areas of varying shades of green. The younger 

 eggs are crowded from the surface, to find their positions below 



