24 INTRODUCTION. 



their natural situation on the shore. In less than a week 

 a thin film was discovered on the surface of the pebbles. 

 It gradually increased in breadth and thickness, until at last 

 he observed buds arising from the membrane. These 

 central shoots increased in size, but not rapidly after the 

 first efTorts ; and as he had not an opportunity of placing 

 them in a rock-pool, owing to his being miles from the 

 shore, he discontinued the experiments. 



More recently Algae have been raised from seed by 

 J. A. Agardh and by some naturalists in our own country, 

 but still much remains to be done. Even young Algolo- 

 gists might make experiments in this department. I confess 

 that I have done little in this wav myself, and the little 

 that 1 have done has been conducted in such a manner as to 

 lead to no practical results. Yet it has not been without 

 interest, and I shall therefore mention it as an encourage- 

 ment to my young friends, who may have more time on 

 their hands and more dexterity. 



In the very end of September, 1848, D. Landsboroiigh, 

 jun., had brought from the sea some rare IXudibranchs, 

 which he put in a tumbler of sea-water and placed in a 

 window with a south-east exposure. They lived there for 

 several weeks, and when they began to look feeble, they were 



