JOTTINGS FROM MY NOTE-BOOK. 211 



XXII. 



JOTTINGS FROM MY NOTE-BOOK. 



BY DAVID ROBERTSON, F.L.S., F.G.S. 



On the local distribution of Pennatula phos- 



PHOREA, Lin., VlRGULARIA MIRABILIS, Lam., and 



Pavonaria quadrangularis, Pall. 



[Read 7th June, 1887.] 



It scarcely need be said that some marine animals 

 frequent particular portions of the sea-bottom where 

 certain conditions prevail — as sand, gravel, and mud — 

 while others seek the weedy shores both above and 

 below low-water. Although the known habitat of 

 an animal may be mud, it does not necessarily 

 follow that the species will be found generally 

 distributed over the whole mud area of the district. 

 Some species are crowded together on particular 

 spots ; yet this may not always arise from the 

 gregarious habits or social associations of the 

 animals, but from other physical conditions. Some 

 may have a great power of multiplying their kind, 

 with little power of moving from one place to 

 another ; and when the place proves favourable for 

 their healthy development, they seem to want the 

 will or the power to wander from it. The habitat 

 of the animals that I now bring under your notice 

 is in mud, but they do not seem to have much (if 

 any) power of locomotion. In early stages they may, 

 like many others, have the power of floating away 

 with the currents ; but this power does not appear 

 to manifest itself to any great extent in the case of 

 these under consideration. 



During the present spring, when a haul of the 

 dredge was being taken by the yacht Medusa (of 



