RELATIONS OF INSECTS TO OTHER ARTHROPODA 11 



originally derived from the setiparous glands in the appendages 

 (parapodia) of annelid worms. 



The genital glands and ducts are paired, but it is to be observed 

 that the outlets are single and situated at the end of the body. In 

 the male the ejaculatory duct is single ; in its base a spermatophore 

 is formed. It will be seen, then, that Peripatus is not only a com- 

 posite type, and a connecting link between worms and tracheate 

 arthropods, but that it may reasonably be regarded, if not itself 

 the ancestor, as resembling the probable progenitor of myriopods 



FIG. 4. E, Peripatus ed-icttfilnii, heart from the under side: a, base of antenna; op, oral 

 papilla ; the figure also shows the papilliv around the mouth, and the four jaws. After Balfonr, 

 from Lang. F, Anterior end of Pf-ripuilis <'njie-nnin, ventral sick', laid open : n, antenna ; 2, tongue ; 

 k, jaw : ml, salivary gland ; gn, union of the two salivary glands ; ph. pharynx ; tx, oesophagus ; /, 

 lip pnpillii- around the mouth; op, oral or slime papilla ; aid, duct or reservoir of the slitne gland. 

 After Balfonr, from Lang. 



and insects, though of course there is a very wide gap between 

 Peripatus and the other antennate, air-breathing Arthropoda. 



Relation of Myriopods to Insects. The Myriopoda are the nearest 

 allies of the insects. They have a distinct head, with one pair of 

 antenna?. The eyes are simple, with the exception of a single genus 

 (Cermatia), in which they are aggregated or compound. The trunk 

 or body behind the head is, as a rule, long and slender, and com- 

 posed of a large but variable number of segments, of equal size and 

 shape, bearing jointed legs, which invariably end in a single claw. 



The mouth-parts of the myriopods are so different in shape and 

 general function from those of insects, that this character, together 

 with the equally segmented nature of the portion of the body behind 

 the head (the trunk), forbids our merging them, as some have been 



