MY Rl APOD A 



395 



deeply into the multilayered ectoderm to become the middle-strand nerve 

 cells (Fig. 351, mst). (This section is taken tangent to the pit which 

 therefore does not show.) The middle-strand nerve cells later form a 

 band that connects with the membrana ventralis (Fig. 348, mst). The 

 overgrowth of the ganglia by the epidermis, their separation from it, and 

 the subsequent contraction of the middle-strand nerve-cell band result 

 in bringing the right and left ganglion toward the median line where they 



mes 



mes 



mst 



Pig. 351. — Scolopendra cingulata. Cross section of trunk, left half, (mes) Mesoderm. 

 {mst) Median strand, (p) Leg. {vm) Membrana ventralis. {Adapted from Heymons.) 



later fuse into a single ganglion (Figs. 348, 352, ggv, mst). Certain cells in 

 contact with the ganglion cells laterally, which were drawn in with them, 

 develop into the neurilemma. Before the median fusion of the ganglia, 

 the neuropilar fibers form a continuous longitudinal strand without 

 neuroglia cells. After the first molt and after fusion of the ganglia, 

 neuroglia cells, probably originating from the middle cell strand, are 

 interspersed. Thus the connectives arise. With the fusion of the 



vm 



Fig. 352. — Scolopendra dalmatica. Cross section of anlage of a rump ganglion, (bl) 

 Blood cell, (coel) Coelome. {ep) Epidermis, (ggv) Ganglion pit. (mst) Median strand. 

 {mus) Muscle, (n) Nerve, {neur. p) Neuropile. {sin) Sinus, {vbl) Vasoblasts. {vm) 

 Membrana ventralis. {Adapted from Heymons.) 



ganglia along the median line the middle strand is enclosed, while fibers 

 passing transversely from each ganglion unite with the fibers of the neuro- 

 pile to form the commissures. These, however, are not sharply differ- 

 entiated in Scolopendra. From the mesoderm a peritoneum is developed 

 covering the entire nerve cord. Lateral nerves develop early from each 

 ganglion, becoming elongated when the ganglia migrate toward the center 

 line. The nerve cord, exclusive of the subesophageal ganglion, consists of 



