168 ZOOLOGY: 
Those members of the armed Gephyrea whose developement 
has been investigated show unmistakable affinities to the 
Chaetopods. Their larvae exhibit a metameric segmentation, 
but the somites disappear early. Traces of segmentation are 
retained in the adult in a few cases, such as the four pairs of 
nephridia in one species of Zhalassema, the double ring of 
setae in Eehiurus Pallasii, and possibly in the rings of hooks 
and circular nerves of many forms. A connecting link between 
the Gephyrea armata and the Chaetopoda may exist in the 
curious worm Sternaspis. This animal, usually classed with 
the Chaetopoda, retains a well-marked segmentation ; and its 
blood - vessels, whilst resembling in their disposition the 
more important vessels of the Gephyrea, open into a well- 
developed system of capillaries. On the other hand the looped 
intestine, one pair of brown tubes, retractile anterior end of its 
body, and—in Sternaspis spinosa—a long bifid prostomium, de- 
scribed by Sluiter, are all features shared in common with the 
Gephyrea. 
The unarmed Gephyrea have an abbreviated developement 
which shows no traces of metameric segmentation, but this 
hardly seems a sufticiently important difference to warrant the 
breaking up of the group. 
