122 GEOEGO ORIHAY SHINJI 



depression, but it gradually elongates to form a long folded tube. 

 Only the dorsal wall of the invagination becomes the embryo 

 proper, while the ventral wall gradually transforms into the 

 amniotic layer. 



The second maxillae, first maxillae, thoracic legs, mandibles, 

 antennae, and labrum appear in the order given. As the brain 

 grows enormously in size, the amnion in front of the brain is 

 pushed against the serosa, with which it finally fuses. At this 

 point of fusion a rupture occurs, through which the embryo 

 emerges, first the head, then gradually the rest of the body, and 

 thus it rotates around the transverse axis of the egg, with the 

 result that the poles of the egg and those of the embryo coincide. 



A short time before the revolution, a large ventral middle 

 invagination occurs between the maxillae. At the time of the 

 completion of the revolution this invagination forms the ventral 

 cavity. The mandible and the first maxilla each produces, 

 from its distal or pointed end, a long chitinous bristle or oral 

 seta, while the labrum and the second maxilla together form a 

 box-like framework. 



5. A short time before the egg passes into the oviduct, a colony 

 of globular (Icerya) or rod-shaped (Lecaniodiaspis) organisms mi- 

 grate into the egg through the follicular epithelial cells situated 

 at the anterior (Pseudococcus and Lecaniodiaspis) or posterior 

 end of the egg (Icerya). The germ cells, the first definitive cells, 

 migrate toward this colony of organisms and surround it. In the 

 case of Icerya, the germ cells, as well as the colony of the parasitic 

 organisms, are actually pushed forward by the invagination of 

 the germ band to a point a short distance from the anterior end 

 of the egg. Then both the germ cells and colony of the 

 parasitic organisms become stationary and do not accompany the 

 further elongation of the germ band. In the case of Pseudococcus 

 and Lecaniodiaspis, the germ cells which are formed at the 

 posterior end of the egg, voluntarily migrate toward the colony of 

 organisms located near the opposite end of the egg. From the 

 colony of organisms the germ cells later migrate toward the tip 

 of the invagination and form two definitive ovaries. 



6. In coccids there is a true gastrula. The entoderm, mesoderm, 

 and ectoderm are all continuous at the tip of the invagination. 



