No. 2.] EMBRYOLOGY OF THE AMERICAN LOBSTER. 223 



clearly show the interlacing bands of muscle fibre. The greatly 

 enlarged egg-cells have crowded the smaller into the inter- 

 stices, and many have been driven from periphery to centre by 

 the growth of their fellows. The cells of the follicular epithe- 

 lium are seen in cross-section (Fig. 1 1) as nucleated bands of 

 tissue enclosing the egg-cells. In places where the knife has 

 cut tangentially across these bands, a higher power shows innu- 

 merable pavement epithelial cells and traces of connective tissue 

 and blood-cells. The thick-walled blood-sinuses of the early 

 ovary are no longer prominent, and the primitively radiate 

 structure has become entirely obliterated. 



Immediately after oviposition the ovary presents a torn and 

 tattered condition. The shreds of connective tissue and follicu- 

 lar epithelium extend out into the lumen of the organ, giving 

 cross-sections a spongy appearance very different from that 

 presented at other times. The eggs to be next deposited are 

 opaque white in color, and do not acquire the green shade until 

 two or three weeks after oviposition. 



The Ovarian Egg. 



The ovary of a small female lobster presents the youngest 

 ovarian eggs. These are in groups and clusters not clearly 

 defined (PL XVI, Fig. 10, E-c l ). The elongated and more or 

 less homogeneous nucleus occupies nearly the entire cell. In 

 sections a plasmodium-like appearance is often presented, and 

 cases of apparent fusion of cells, as already stated, are not infre- 

 quent. The egg-cells are at this time indistinguishable from 

 the cells which may ultimately form follicular epithelium. 

 Small particles of chromatin, or at least particles that absorb 

 the stain, are often scattered over and around the nuclei and 

 between the cells. 



Associated with the above-described elements are cells slightly 

 older, which have taken on structures that foreshadow their 

 ultimate condition. The nucleus is more clearly defined, it is 

 distinctly granular, and a surrounding layer of homogeneous 

 protoplasm is evident. Such a cell is figured on PL XVI, Fig. 

 10, E-c 2 . As the earlier cells may fuse, so these are at times 

 found flowing together. A slightly older egg-cell is found at 

 E-c 3 . The layer of protoplasm has become deeper, but the 



