1908- 1909.] Glimpses of Marine Life on the Forth. 119 



are of course nutritious particles of organic origin : the sand 

 may serve merely to dilute its food, or for that matter to 

 season it ; in any case, the worm's digestion must be par- 

 ticularly good. By the contraction of our facial muscles we 

 can draw down our brows, but this power is immensely greater 

 in Arenicola and other annelids : the worm not only draws 

 down its brows but swallows its nose and scalp as well. The 

 prostomium or proboscis admits of introversion, whereby the 

 •external surface comes to be internal : the process is analogous 

 to turning a stocking outside in, — or " flyping " it, as we say 

 in Scotland. When the prostomium is retracted, the scales 

 on its outside scoop up the sand or mud and convey it into 

 the worm's interior, like the buckets in one of the dredgers 

 employed in deepening harbours; indeed Arenicola might 

 fairly be described as an animated dredging - machine. In 

 this way it makes its burrow, coming to the surface from time 

 to time to deposit the excavated materials. The sides of the 

 shaft are prevented from falling in by a secretion of mucus, 

 and the proprietor pulls himself out and in with the aid of 

 his bristles. 



Pectinaria, one of the tubicolar annelids, constructs a very 

 perfect tube. Just under the southern viaduct of the Forth 

 Bridge we found a very fine specimen, with the inhabitant 

 still inside. The tube is almost three inches long, half an 

 inch in diameter, and built up entirely of particles of sand 

 cemented together into a perfectly smooth cylinder. One 

 could hardly refrain from recalling the great iron caissons 

 sunk in laying the foundations for the neighbouring piers of 

 the bridge : it would tax the skill of our engineers, however, 

 to construct a cofferdam that could bear comparison with the 

 exquisite workmanship of Pectinaria. 



The tubes of Terebella, the sand -mason, are much more 

 abundant : they project an inch or two above the sand, and 

 are easily recognised by their fringed extremities. The tube 

 in this case is of much rougher workmanship, pieces of shell 

 being largely used in its construction. Sabellaria is of social 

 habits ; its tubes are crowded together and form masses re- 

 sembling sandstone or concrete. At Limpetness, on the Naval 

 Base, the Admiralty have been anticipated in the formation of 



