ALG^. 1 37 



as animal than vegetable. It Is only to be regretted 

 that we know so little of the history of the life and 

 development of these beings, for we refuse to charac- 

 terize some forms as animal on the sole ground that 

 we do not find in them that movement which is the 

 property of animal nature." ^ We must leave these 

 speculations as they were, and proceed with our 

 record, for manifestly they bring us no nearer to a 

 solution. 



Another instance of the abundant production of a 

 minute alga in a lake, so as to impart a characteristic 

 colour, is recorded by Mr. W. Thompson. " Late in 

 the autumn of 1S37," he says, "I observed patches 

 of a singular bluish-green scum at the edge of Bally- 

 drain Lake, a few miles from Belfast, but when I 

 returned soon afterwards it had disappeared. On 

 visiting the lake in July, 1838, I found that the whole 

 body of water was tinged with a dull faint glaucous 

 hue. On going out in a boat to ascertain the cause, 

 I saw that the water was everywhere filled with ex- 

 tremely minute particles, which might be compared 

 to motes in a sunbeam. To the unassisted eye they 

 seemed as delicate as the finest human hair, and of a 

 spiral form. Around the boat their motion was not 

 very rapid, but those on the surface moved in an 

 opposite direction from the particles beneath, and 

 the latter the more quickly. On inquiry from some 

 relatives, who reside on the borders of the lake, I 

 learned that the appearance had been observed only 

 for the last four or five years, and for about three 

 months in each year. One of my friends had looked 



' Annals and Magazine of Natural History^ Nov., 1839, p. 214. 



