Now2.)) A77CRODEUTOPRCS (GRYLEOTALPA COSTA. 309 
22-24-cell stage. — Figs. 5-8 show four views of an egg of 
the 22-cell stage, Fig. 5 representing the macromere pole of 
the egg. In this stage A, Bb, C, D, G, and # have given rise 
to At, A’, B, B*, etc., by an equatorial cleavage (Fig. 8), while 
£ and Fare still in the act of dividing and the micromeres show 
no trace of division. 
jo-cell stage. — Figs. 22-24 show three views of an egg of 
thirty cells passing into the 42-cell stage. The cells E and & 
have sgiven Tse: to 22) 227A, and) 7777(fic. 22) ihe cells'a 
and c, 6 and d@ have all divided, forming a’-a%, cc’, and 6°62, 
a*—d’, while g@ and h*, x and y are the descendants of g and Z%. 
Instead of the division being by an equatorial plane in these 
cells, as it is in the macromeres, and as Van Beneden and 
Bessels ('69), Rossiiskaya ('90), Della Valle (93), and Ulianin 
(81) found it for the micromeres of other amphipods, it is 
vertical and at right angles to the last plane of division of 
these cells, which also was vertical (Figs. 3, 4). That the divi- 
sion of the micromeres at this time is vertical and not equa- 
torial in Microdeutopus is shown by the spindles in g and / 
(Fig.11). I havealso seen spindles in 6 and d@ lying in the equa- 
torial plane and at right angles to those shown in g and 4; z.2., 
in the direction of the arrows in the cells 4 and d (Fig. 11). 
Figs: 11,02 show the protoplasm in A, .A% 52 Bb C+, C42. 
D divided and the yolk deeply constricted; the nuclei of G, 
ff in the aster, and of g, / in the diaster stage. In Figs. 24, 
25 G’, 77/2 are beginning to divide; in. G?; 27 the process is 
further advanced, and g and % have divided completely. The 
daughter cells of g and ZI shall name g*, h*, x, and y, the x, y 
cells being those lying next to 6°-6%, d*-d’. These are 
always present before G*, H/ have divided, although e and 7, 
the cells corresponding to g and 4, upon the other side, show 
no trace of division until a much later period (about the 72-cell 
stage). It is interesting to note that the cells of the A/ and 
ef groups divide later than those of the GH and gh groups. 
It may be that the ZF cell corresponds to the smaller cell 
which Della Valle ('93) found to result from the second division 
in Orchestia. He describes this cell as lagging behind the 
others in development. 
