Introduction to Animal Morphology. 379 



a lateral row of venous ostia ; it is kept in its place 

 by triangular musculi alares attached to the body wall, 

 and gives off from each chamber a pair of arteries for 

 each somite. The front chamber sends off medially a 

 cephalic branch, and on each side a branch which 

 surrounds the oesophagus as a pair of rings, which 

 uniting form the large blood sinus that accompanies 

 the ventral nerve cord (thus like the arrangement in 

 the Scorpion). There is no venous nor capillary 

 system, nor a pericardial sinus, but the blood flows 

 in lacunae and perivisceral spaces. 



The paired tracheae open ventrally or laterally, 

 and may be equal to (Geophilus), or fewer than 

 (Scolopendra), the number of segments. In lulus a 

 bundle of simple or slightly branchednon-anastomosing 

 tubes passes from each stigma ; in Glomeris they are 

 branched ; in Scolopendra they have free longitudinal 

 and transverse anastomoses ; in Lithobius and Scolo- 

 pendra, stigma-bearing and stigma-less segments 

 alternate. 



Scattered on the surface are often, pear-shaped 

 glands, secreting a brown, corrosive fluid, with a very- 

 disagreeable smell, opening by dorsal pores (foramina 

 repugnatoria). The thorax and abdomen are not 

 differentiated, and each segment bears ventrally, either 

 near the middle line or laterally, 1-2 pair of 6-7 

 jointed legs, which on all segments are alike, with 

 single or double end-claws. 



They are dioecious, oviparous. The whole yelk 

 cleaves, and the food yelk lies outside the wall of the 

 alimentary canal, between it and the integument. The 

 ovary is either a single pouch, with a single or double 

 oviduct, or is double (Craspedosoma), united anteriorly, 



