MY RI APOD A 



385 



Segmentation of the Germ Band and Appearance of Appendages. — 

 When the germ disk has somewhat lengthened until it is about twice as 

 long as the broadened anterior half and before the cephalic end is sharply 

 differentiated from the blastoderm in front, the first indication of meso- 

 dermic segmentation becomes apparent by the formation of three seg- 

 ments some distance from the posterior end of the disk. At this time the 

 mouth may be seen as a slight depression at the anterior end. In this 

 region the mesoderm is lacking on the median line. With the increasing 

 length of the embryonic rudiment, which we may now call the "germ 



v-pren 



c >:■ vm V,— 



p21 





prz 



tel 



terl2 



A B 



Fig. 341. — Scolopendra cingulata. A, germ band. B, lateral aspect, later stage than 

 that of Fig. 342. (ant) Antenna, {dm) Membrana dorsalis. (Ir) Labrum. (md) 

 Mandible, (mpd) Maxilliped. (mx) Maxilla, (p) Leg. (pren) Preantenna. (prz) 

 Proliferation zone, (ste.r) Sternite. (tel) Telson. (ter) Tergite. (vm) Membrana 

 ventralis. (Adapted from Heymons.) 



band," more segments appear, and the anal opening becomes visible close 

 to the posterior end. 



In front of the crescent-shaped oral invagination the clypeus develops 

 as an unpaired lobe, and at some distance posterior to this invagination 

 the rudiments of the antennae appear. Between the posterior margin 

 of the antennal segment and the anterior margin of the mandibular seg- 

 ment the intercalary segment is apparent, though it does not develop so 

 fully as the other metameres, nor will it bear appendages. Two maxil- 

 lary, one maxillipedal, 21 rump, and a relatively large, cordate telson, or 

 anus-bearing segment, make up the remainder of the body. 



