1904.] NATURAL SCIENCES OF PHILADELPHIA. 353 

Ist. 2d. 3d. 4th. 

2a 121 211 122 | 212 





da | ot | jay! | S19 "| 1290 
(or 22) | 






The table should be read: In A quadrant 2a”! cleaves first, 2a”! second, 
2a™ third and 2a” fourth. In B quadrant, etc. Cleavages in A 
quadrant are found in figs. 50, 58 and 63; in B, figs. 52 and 59; in C, 
figs. 44, 48, 54, 60 and 65; in D, figs. 47, 51 and 61. 
The divisions of 2a!?"-2d™! are leotropic in all quadrants, of 2a?1-2d?"" 
universally dexiotropic, of 2a7-2d? everywhere dexiotropic, while 
variation is found in the direction of cleavage in the cells 2a’-2d™. 
Of these latter a decidedly leotropic direction is found in B quadrant, 
horizontal to dexiotropic in D, horizontal to leotropic in A and ap- 
proximately horizontal in C. With regard to the size of the derivative 
cells, it may be said in a general way that variation is evident. More 
particularly considered the following conditions are found to prevail. 
The divisions of 2a”, 2c#!, 2d result in cells of equal size, while in 
the case of 2b”! the upper cell 2b”! is much smaller than 2b”; 2a7, 
2b*?, 2d?" form upper small and lower larger parts, while 2c”! divides 
equally; 2b?, 2c?”, and 2d” show similar divisions into upper small 
and lower large cells, while 2a7? remains so long undivided that its 
derivatives are uncertain; 2a'”-2d™ divide equally. 
As a result of the foregoing cleavages the second quartet contains 
in all approximately forty cells. The irregularities which have char- 
acterized the preceding divisions are increased in number as cleavage 
continues, though until a much later period all four quadrants show 
relatively the same number of cells for this quartet. If figs. 67-70, 
representing the different sides of the same egg, be examined it will 
be seen that in A quadrant 2a” has divided dexiotropically, while 
2a has divided horizontally; quadrant B shows no further multi- 
plication of elements; in C quadrant, 2c" is in process of division, while 
2c744t and 2c?4? have both given off small cells toward the upper pole; 
D quadrant remains as before. 
23 
