EMBRYONIC DE\^LOPMENT OF THE MANTID 227 



tion that the indusium begins its rapid growth and envelopment 

 of the yolk. In P. sinensis the indusium is not further developed. 

 I offer the suggestion that it is simply pulled over the embryonic 

 rudiment as the amnio-serosal fold progresses to form the embry- 

 onic envelopes. Accepting my idea of homology, therefore, 

 readily explains the presence of this structure and offers an 

 explanation of its unique position in the serosa. The organ 

 persists in place, apparently firmly attached to the vitelline 

 membrane, until sometime after completion of revolution, when 

 it frees itself and is ingested by the embryo during the formation 

 of the dorsal walls. This structure is clearly not to be called 

 the dorsal organ, though it may become part of it, as will be 

 evident presently. Another organ later makes its appearance 

 which answers very satisfactorily to Wheeler's ('89) definition 

 of a dorsal organ. "The term 'dorsal organ' has been applied 

 to the peculiar thick lump of cells resulting from the concentra- 

 tion on the dorsal yolk of the remains of either the amnion or 

 serosa, or of both, preparatory to their sinking into the yolk and 

 being absorbed." 



Definitive segmentation and the appendages. Referring again 

 to the small area of cells posterior to the thoracic region, active 

 growth takes place as soon as the lateral development of the 

 thoracic region has proceeded to its completion for the present, 

 as shown in figure 2. As the definitive thoracic segments are 

 becoming visibly outlined by the grouping of the cells, this 

 posterior mass is rapidly developing caudally to form the ab- 

 dominal segments. It is during this extension that the antennal, 

 buccal, thoracic and abdominal rudiments first make their 

 appearance. 



The antennal rudiments originate as the result of a rapid 

 multiplication of cells in a rather restricted area on the hind 

 margin of the cephalic lobes, a little less than half way between 

 their margins and the median line. Immediately behind this 

 area a strip of clear cytoplasm is apparent, making the antennal 

 proliferations even more noticeable. This very rapid cell 

 division crowds a large number of cells with little cytoplasm into 

 a compact mass. As growth continues, the tendency is appar- 



