\lROULAi:l.\ MIKABir.IS. 75 



Couceruiug the nieclianism of retraction it is difficult to form any 

 precise idea. From the descriptions it would appear to be a muscular 

 action effected probably by the powerful muscular system of the stalk 

 and rachis. 



Some experiments made by Dalyell show well the efficiency of these 

 muscles. He found that in living specimens the muscles of the 

 rachis frequently cause the fleshy part to twist itself in a spiral 

 manner round the stem, and then sti'aighten out again. " A section, 

 six or eight inches long, standing inclined in a narrow jar, will be 

 found to have arranged itself in a single volute throughout, or into 

 two, three, or four between night and morning. The whole can relax 

 again into a straight line by their obliteration." * 



KoUikerf suggests that the boring into the sand is effected by peri- 

 staltic waves of dilatation and contraction passing down the stalk and 

 rachis : the dilated parts acting as fulcra by completely filling up the 

 hole in which the stalk is planted, and so fixing it at one point, while 

 the wave of contraction, passing down below this fixed point, would 

 drive the end of the stalk deeper into the mud. The fixed point would 

 then relax, the terminal vesicle would dilate to act as a fulcrum, and 

 the longitudinal muscles would pull the whole colony down. It is, 

 however, not easj' to see how a rapid retraction could be effected in 

 this manner. 



3. — Supposed Nocturnal Habits. — According to Dalyell, Virgularia 

 when in captivity " remains contracted during the greater part of the 

 day, and the organs are seldom displayed before five or six in the 

 afternoon." On this point we would refer to the observations made 

 when considering the saine statement concerning Pennatula. We have 

 there suggested that Pennatula appears to be "nocturnal" when 

 brought to the surface, simply because the amount of light it receives 

 in broad daylight is vastly in excess of what it receives normally at 

 the sea bottom, and that it is only towards evening that it is placed 

 under what to it are normal conditions as to amount of light. 



8. — Geographical distribution. 



V. mirabilis has been taken at a number of localities in different 

 parts of Europe. Like the Pennatulida generally it appears to be very 

 local, but to occur in large numbers where it is found at all. 



It has been recorded from several places on the coast of Norway 

 and Denmark ; from Belfast Lough, Gairloch, Oban, the island of 

 Inchkeith, near to Ediuburgli, the Hebrides, and other Scotch 

 localities. 



In 1879 the Birmingham Natural History Society added a new 

 locality to the list by dredging a single specimen off Falmouth ; and we 

 may cite also, on Mr. Darbishire's authority, the stomachs of haddock 

 off Scarborough, as a place where Virgularia has been found. The 

 uncertainty whether these last specimens had been found by the 



* Dalyell : op. cit., p. ISo. t Kulliker : op. cit., p. 305. 



