EMBRYONIC DEVELOPMENT OF THE MANTID 231 



It is unique among observed insect embryos in at least two 

 respects : first, the embryo reaches the dorsal yolk by means of a 

 lateral or sidewise migration instead of proceeding head first or 

 tail first as is commonly the case: second, the embryo, after 

 arriving in position on top of the egg, remains there for the rest 

 of its embryonic growth and even on hatching works its way 

 out of the ootheca from this position. The usual revolution of 

 hexapod embryos, when such a movement occurs, is followed 

 later by some sort of reversal during which the embryo returns 

 to its original position. 



Growth during revolution. Growth continues during the fore- 

 going movement, and very early there can be perceived a tend- 

 ency toward a general thickening of the entire embryo. It 

 becomes broader, covering a larger proportion of the yolk; it 

 also elongates. By the time it is in a mid-lateral position; the 

 antennal, maxillary and thoracic appendages, instead of appear- 

 ing as mere finger-like projections, have become considerably 

 elongated and exhibit, as well, definitive segmentation, though 

 this is far from complete. The first abdominal segment has 

 developed a pair of elongate conical processes, which are primi- 

 tive appendages. The tracheal invaginations are unusually dis- 

 tinct and the telson is undergoing several modifications. The 

 abdomen shows ten definitive segments and with the telson, eleven 

 in all. The last three are ventrally flexed. 



When the embryo reaches the dorsal surface of the egg it 

 appears as in figure 4. We note at once the rapid development 

 that has taken place in the whole embryo and particularly in 

 the appendages. The procephalon is clearly outlined, the optic 

 plates are heavily pigmented and the tritocerebrum is drawn 

 up under the procephalon. The buccal segments are likewise 

 drawn forward into a more compact mass. The thoracic region 

 is as broad as the cephalic area, and all of the appendages shov/ 

 greater or less signs of segmentation. The first abdominal 

 appendages are still relatively long and project diagonally out- 

 ward. The following pairs are certainly reduced in size. In 

 fact they rapidly flatten out and a little later apparently form 

 the margins of the sternites. As a result of the disappearance 



