624 MARGARET ROBINSON. 



EXPLANATION OF PLATE 37, 



Illustrating Miss M. Robiusou's paper " On the Segmenta- 

 tion of the Head of Diplopoda." 



Reference Letters. 



Ag. Aiitennary ganglion. Ant. Antenna. Arc. Arcliicerebrum. Clj/. 

 Cl^'peus. Ec. Ectoderm, if. Moulli. Md. Mandible. Mdg. Ganglion of 

 mandibular segment. Mes, Mesoderm. Mx'. First maxilla. Mx'g. Ganglion 

 of first maxilla segment. Mx". Second maxilla. Mx'g. Ganglion of second 

 maxilla segment. Pmx. Post-maxillary segment. Pmxg. Ganglion of post- 

 maxillary segment. Pmxt. Post-maxillary tergum. Pre. Proceplialic lobe. 

 Isf. Intersegmental furrow. Trc. Trito-cerebral segment. Trcg. Trilo- 

 cerebral ganglion. 



Fig. 1. — Embryo of Arcbispirostreptus (sixteen days old) about four 

 days before leaving the shell. 



Fig. 2. — Embryo of Arcbispirostreptus one day before leaving the shell 



Fig. 3. — Larva of Arcbispirostreptus five days after hatching. 



Fig. 4. — Longitudinal section through a|)pendages of embryo shown in fig. 2. 



Fig. 5. — Longitudinal sectiou through ganglia of embryo shown in fig. 2. 



Fig. G. — Longitudinal section through the suboesophageal and post-maxil- 

 lary ganglia iu the adult Spirostreptus. 



