No. 3-] THE EMBRYOLOGY OF A TERMITE. 517 



shown in the figure. Near the lateral and posterior boundaries, 

 as well as in the center, the nuclei are about equally distributed 

 and lie rather close together. Turning to the older stage (PL 

 XXX, Fig. 13), it is evident that the nuclei in the lateral por- 

 tions of the same area are fewer than in the younger Q.gg, and 

 nearly twice the distance apart. The Qgg (PI. XXX, Fig. 14), 

 being rolled slightly on one side (though not nearly so much so 

 as PL XXX, Fig. ii^, with which it must not be compared), 

 shows this better than PL XXX, Fig. 13, in which the convexity 

 of the surface makes it impossible to give an accurate idea of 

 the distribution of the nuclei at the sides. The letters l.b.d. 

 indicate a like region in both figures (PL XXX, Figs. 13 and 

 14). It is the portion of the surface lying outside of (lateral to) 

 the position marked by these letters that shows a diminution in 

 the number and a wider separation of the nuclei, as compared 

 with the previous stage. 



These changes within the limits of the posterior half of the 

 ventral surface, between the stages of PL XXX, Figs. 12 and 

 13, resulting in a perceptible diminution in the number of nuclei 

 laterally, with an increased crowding toward the center, appar- 

 ently necessitate an active migration of cells centripetally, 

 cooperating with cell multiplication, to establish the embryonic 

 disc. 



PL XXX, Fig. 15, is an example of an older o^gg, showing an 

 extreme concentration of the embryonic disc. 



In PL XXX, Fig. 18, which represents the ventral surface at 

 a much later stage, the embryonic region, now appearing as a 

 conspicuous and sharply defined circular disc of nucleated 

 protoplasm, hardly occupies one-half of the area formerly 

 marked ca. The surrounding cells are few and widely scat- 

 tered, while the comparatively broad, crowded area in the 

 earlier figures (PL XXX, Figs. 12 and 13) has contracted to the 

 smaller, densely crowded, circular embryonic rudiment. There 

 is a marked concentration in the germ-disp visible in passing 

 from the stage shown in PL XXX, Fig. 17, to that of PL XXX, 

 Fig. 18. Note the concentric crowding of the nuclei along the 

 sides of the disc in PL XXX, Fig. 18, as compared with the 

 preceding figure. 



