No. 3-] THE EMBRYOLOGY OF A TERMITE. 525 



this section and the following ones, fine protoplasmic processes 

 running out from the ectoderm. In some instances I have 

 traced such threads out to the chorion and into the micropylar 

 funnels. 



As the cells of the amniotic fold have multiplied, it has bent 

 well forward in the next figure (PI. XXXI, Fig. 34). Its cells 

 form a thick mass and are arranged in two layers. Posteriorly 

 it passes into the ectoderm through the thinned region pointed 

 out in the former stage. The flat serosal cells lie superficially 

 drawn forward with the amnion. The mesodermal plug is 

 more sharply defined from the ectoderm, its cells lying loosely 

 together in the former position and dividing in places. 



When the amniotic cavity is finally closed completely (PI. 

 XXXI, Fig. 35), as in PL XXXI, Fig. 24, from the surface, the 

 resemblance between the amnion and the ectoderm is most strik- 

 ing. The cells of both are arranged in two layers and divide in 

 a similar manner. The serosa is now a very thin membrane of 

 large, flat cells, stretching over the embryo and enclosing the 

 yolk. Its nuclei are found, from now on, in resting condition, 

 with one or more nucleoli and granular looking chromatin. They 

 divide seldom. The mesoderm is now sharply separated from 

 the ectoderm, and from this time the separation appears to be 

 maintained. A few mesoderm cells have pushed back to the 

 extreme posterior end of the embryo. At the anterior end the 

 former relations remain unchanged. The yolk-cell nuclei are 

 of remarkable size and have apparently remained undivided 

 from an early stage. 



Growth of the Disc-Shaped Embryonic Rudiment into 



AN Elongated Germ-Band up to the Time 



OF ITS Segmentation. 



Comparing PI. XXXI, Fig. 24, with figures of earlier stages, it 

 is evident that considerable change has taken place in the 

 shape of the embryo. The disc has now grown larger. It is 

 about twice as long as broad, and while the posterior end is 

 enlarged and rounded, the anterior extremity is rather pointed. 

 The cells of this disc and of the amnion have become much 



