238 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



proboscis is protruded, pressed into the sand and with- 

 drawn full of sand and again everted. The body is thrust 

 forward partly by the action of the longitudinal muscles 

 of the body wall, and partly by the peristaltic waves pro- 

 duced by the circular muscles, by means of which the 

 anterior end is also rendered swollen and tense, and is 

 thus enabled to enlarge the burrow. By these means a 

 passage is eaten and forced through the sand, smoothed 

 by contact with the skin, and may be lined with mucus 

 secreted by the epidermis. The gill region, being 

 narrower than that which precedes it, is to some extent 

 protected from friction, and the notopodial setse are also 

 directed so as to protect the gills. After burrowing 

 vertically downwards to a depth of from one to two feet, 

 the littoral forms may make a horizontal or oblique 

 gallery, and then a second vertical one, which opens on 

 the surface of the sand in a small funnel-shaped aperture.* 

 The burrows of Laminarian worms, and those of some 

 littoral specimens, are simple vertical excavations (not 

 U-shaped), in which the animal is almost invariably 

 found head downwards. f 



The amount of work done by Arenicola has been 

 estimated by Davison* on the Holy Island Sands. As 

 the result of Observations upon the number and weight of 



* G. Bohn ("Observations Biologiques sur les Arenicoles," Bulletin 

 du Museum d'histoire naturelle, 1903, No. 2, p. 62) states that the 

 burrow of the littoral form is not U-shaped, and that it does not open 

 at the funnel-shaped aperture. He believes that the latter is due to 

 subsidence of the surface sand brought about by the subjacent sand 

 being removed during feeding by the proboscis of the worm. All other 

 observers agree that the burrows are, in the majority of cases, 

 U-shaped. 



f For an account of curious seasonal changes in Arenicola and 

 other burrowing marine animals see G. Bohn, "Les intoxications 

 marines et la vie fouisseuse," Comptes Rendus de l'Academie des 

 Sciences, Paris, tome 133, pp. 593-596 ; and " L'histolyse saisonniere," 

 ibid. pp. 646-648. 



\ Geological Magazine, vol. viii., 1891, p. 489. 



