ORTHOPTEROIDEA (PANORTHOPTERA) 



219 



derm appears late, after the segmentation of the germ band. Yolk cells 

 take no part in its formation. Blastokinesis is accomplished as described 

 and figured for the dragonfly ; amnion and serosa fuse into a single mem- 

 brane at one point, only to tear open over the ventral side of the embryo, 

 the edges of these two envelopes fused, both retracting dorsally, later to 

 form the secondary dorsal organ at the back of the head. The yolk is 

 now contained in a sack whose ventral wall is the embryo and whose 

 lateral and dorsal walls are formed of the 

 amnion and serosa. The head of the 

 embryo now slips up along the ventral 

 surface of the yolk to the anterior end of 

 the egg, while the caudal end comes to lie 

 beneath the micropyles of the opposite end. 

 Finally the j^olk together with the enve- 

 lopes is carried into the mid-gut, the dorsal 

 wall closing over them. The development 

 of organs is not described by Knower. 



PHASMATARIA 



The Walking Stick (Carausius 

 morosus Br.) 



The developmental history of the walk- 

 ing stick has been briefly described by 

 several workers and more extensively by 

 Hammerschmidt (1910), Thomas (1936), 

 Leuzinger, Wiesmann, and Lehmann 

 (1926), the work of the three last-men- 

 tioned authors being the most detailed. 

 As might be expected the development 

 resembles most closely in general features 

 that of the locust. The eggs, which 

 measure over 2 mm. in length, are 

 ellipsoidal and flattened laterally, with 

 is pushed off on emergence of the insect. 

 a small number of cleavage nuclei may be found in the periplasm in 

 the region not far from the posterior pole. These proliferate and give 

 rise to further nuclei that migrate tangentially in the periplasm. They 

 remain sparsely scattered over the surface except at the posterior end, 

 where they form a small heart-shaped embryonic rudiment, which is soon 

 composed of several layers of cells. The cells exclusive of those forming 

 the rudiment constitute the serosa. At a later date, as described by 

 Thomas (1936), the amnion appears around the margin of the embryo and 

 later still covers the ventral face. While the inner layer is still forming, 



Fig. 135B; — Eutermes. Embryo 

 with rudimentary appendages. 

 (ahd) Abdomen. {am) Amnion. 

 (ant) Antenna, {ch) Chorion, {lb) 

 Labium, {md) Mandible, (mx) 

 Maxilla. {ser) Serosa. {th 1) 

 First thoracic leg. {y) Yolk. 



a lid-like operculum which 

 At the time the egg is laid, 



