214 STRUCTURE AND LIFE-HISTORY OF VOLVOX GLOBATOR. 



During the day the majority of the Volvoces contained in a shallow 

 vessel rise to the surface, although they avoid strong direct sunshine, 

 while at night they retire in a cloud to the bottom. 



The astonishing number in which the spheres at times appear in 

 some pool and their equally sudden disappearance, have been frequently 

 remarked. Doubtless a very slight change in external conditions suffices 

 on the one hand to favour the development of countless thousands of 

 young plants, and on the other, either to destroy the vitality of the whole 

 colony, or to drive it to seek refuge in deeper water. 



A curious instance of this sensitiveness to varying conditions of light 

 and heat occurred to myself. I had two shallow vessels in a north 

 window, each containing a goodly supply of Volvox. Cold and inclement 

 weather, which prevailed for weeks together, seemed to check their 

 increase, for I found but few young spheres from day to day among the 

 older ones. Thinking that a moderate degree of warmth would tend to 

 increase my colony, I transferred one vessel, fortunately not both, to the 

 floor of a warm greenhouse. In forty-eight hours all were dead, and in 

 a few days scarcely a vestige remained of the countless corpses which had 

 copiously strewed the bottom of the glass. 



C To be continued.) 



OEIGIN OP THE KOCKS AND SCENEEY OF 

 NOETH WALES.* 



BY J. J. HARRIS TEALL, M.A., F.G.S., ETC., LATE FELLOW OF 



ST. John's college, Cambridge. 



During the early part of the summer which has just closed I spent 

 six weeks in rambling over the hills and through the valleys of North 

 Wales. The object of the visit was not exactly geological, but the nature 

 of the country is such that no person who is at all acquainted with the 

 science of geology can travel through it without noticing a number of 

 most interesting points. I propose this evening to give, in the merest 

 outline, a sketch of the geological features of the district, and to illustrate 

 this sketch as far as possible from my own observation, and by means 

 of specimens collected on the spot. 



I may remind you, by way of introduction, that the region of North 

 Wales is classic ground for the geologist, and that the hills and dales of 

 this most beautiful country have not only been the scene of many a hard 

 fought battle in the early days of British history, but that even in later 

 times they have been the subject of severe disputes between rival schools 

 of geologists. 



* This paper, or rather lecture, was delivered before the Natural Science Section 

 of the Nottingham Literary and Philosophical Society. It contains very little 

 indeed that is original, and only professes to be a somewhat popular account of 

 some of the most interesting points in connection with the geology of North Wales. 

 -J. J. H. T. 



