224 BUMPUS. [Vol. V. 



most characteristic feature is the presence of a nucleolus, 

 though granules are still present and continue to exist for some 

 time. Cases of possible fusion are not difficult to find. 



When the egg-cells have reached the condition shown in Fig. 

 10, E-c i , the nucleus has become most prominent. Its con- 

 tents is seen to consist of a clear fluid in which is extended a 

 reticulum, holding in suspension one, or at times several, deeply- 

 stained, spherical nucleoli. In this respect the early egg-cells 

 of Homarus resemble those of Astacus, but differ from those 

 of Eupagurus, since Mayer (yy) claims for the latter a single 

 nucleolus in all stages. In Homarus when there is but a single 

 nucleolus this is relatively larger than when several are clustered 

 in the same nucleus. The cytoplasm is fine-grained, with scat- 

 tered dots of pigment, and is slightly different in color imme- 

 diately around the nucleus, fading away like a halo towards the 

 periphery. 



When the egg-cells have reached the size of E-c b , the halo- 

 like layer of protoplasm around the nucleus is still more promi- 

 nent, and in specimens stained with lithium picro-carmine an 

 interesting structure is exhibited : the peripheral portion of the 

 egg is found to abound in minute vesicles of varying size and of 

 two kinds, fat and plasmic. The fat vesicles, which are present 

 in many crustacean ova, are abundantly distributed throughout 

 the more peripheral portion of the egg-cell, but take on no color. 

 The plasmic vesicles are, in the present case, almost equally 

 abundant, but differ from the first in selecting, to a limited 

 extent, the color of the stain. The plasmic vesicles are oval, 

 spherical, and at times multipolar. They may be homologous 

 with the " transparent vesicles " of Lereboullet ('62), and in 

 many respects answer to the description of the "yolk-cells" of 

 Agelena as described by Balfour ('80) ; though in the latter case 

 they were not considered in stages earlier than the blastula. 

 Ishikawa ('85) has described very similar bodies as occurring in 

 the "yolk segments" of Atyephira, though appearing later, 

 during the segmentation stages. It is his opinion that they 

 arise from the segmentation nuclei. The " secondary meso- 

 derm " of Reichenbach (86), and the "spores" described by 

 Herrick ('86) as occurring in AlpJieus, are probably related to 

 the structures under discussion. 



Though the nucleus [primordial vesicle], E-c b , is consid- 



