2IO AQUATIC MICROSCOPY FOR BEGINNERS. 



the body concealed in their burrow, the remaining 

 parts protruding into the water, and constantly wav- 

 ing to and fro beyond the edge of the little tubular 

 chimneys which they erect. These little towers are 

 often conspicuous objects on the surface of the mud in 

 shallow still water, the worms instantly disappearing 

 into them at the slightest disturbance. Among certain 

 French and German writers on the subject, there is a 

 difference of opinion as to which end of the worm is 

 buried and which end protrudes into the water. As 

 the protruding parts are continually moving, and as the 

 worms also dart into the mud with such astonishing 

 swiftness, to decide the matter is rather difficult. It 

 is, however, probably the tail end. 



The bristles are comparatively short and appear to 

 be arranged in a single row on each side of the body, 

 whereas there is really an additional row of podal 

 spines on both sides of the worm. These podal spines 

 are entirely retractile, and are therefore often over- 

 . looked unless specially searched for. Even then it will 

 perhaps be necessary to compress the worm rather 

 forcibly between the slide and the cover-glass before, 

 they will become conspicuous. They are but slightly 

 curved, and seem to be forked. 



With very high magnifying power (about eight-hun- 

 dred diameters) some of the bristles present a curious 

 aspect. The free extremity is widened and forked, 

 thetwo prongs of the fork being apparently connected 

 by a thin membrane which is longitudinally striated. 

 Sometimes this membrane splits into fine hairs. These 

 widened bristles are most common on the young 

 worms. 



The bright red blood is contained in two principal 



