EMBRYOLOGY OF COCCIDS 91 



sists of two bands separated by the median groove. In reality, 

 however, the furrow represents the amniotic cavity, the blasto- 

 pore, within the invaginating germ band. The colony of para- 

 sitic organisms was not, at first, in contact with the germ band, 

 but it now appears as though it were in the same relative position 

 as in the case of the cottony cushion scale. 



As the invagination proceeds further, the caudal portion of the 

 invaginating germ band curls up ventrally, assuming the shape 

 of the letter 'S.' Each turn of the invagination represents a 

 particular region or division of the body of the embryo as should 

 have been brought out earlier. The germ band at the stage 

 last described consists .of four main divisions, representing the 

 cephalic, the oral, the thoracic, and the abdominal regions, (figs. 

 46, 50, and 64). These regions are shown in figure 6, separated 

 by three dark areas. The two remaining regions cannot be 

 shown very well in the picture, but their presence is represented. 

 Each dark area indicates the junction of two adjacent regions. 



It should also be mentioned that the preoral and abdominal 

 regions are much less extensive in length as compared with the 

 oral or thoracic region. The colony of parasitic organisms, 

 which had been located near the growing tip of the germ band 

 of the cottony cushion scale, now becomes fixed, so to speak, 

 at the region of the second and third abdominal segments and 

 does not accompany the growth of the abdominal region beyond 

 these segments. The condition described for the cottony cush- 

 ion scale is accomplished in an altogether different manner 

 in the case of the mealy bug and Lecaniodiaspis. Instead of 

 pushing the colony of parasites forward, the germ bands of these 

 two species sends out a few germ cells at first, then follows a 

 mesodermal extension to the colony, which establishes a relation 

 with the latter, just as in the case of Icerya. During this stage 

 a pair of somewhat curved, dark elevations appear, one on each 

 side of the germ band near the blastopore. These, as will be 

 seen later, are the rudiments of the brain. In the next stage 

 (fig. 66), the first rudiments of appendages, the second maxillae, 

 become apparent. The abdominal region is very much elon- 

 gated beyond the colony of parasitic organisms. The division of 



