76 Miscellaneous. 



The author adds that the vesicating power of these insects resides 

 in all the soft internal parts, and not, as stated by M. Farines of the 

 common Cantharides, only in the soft parts of thethorax and abdomen. 

 He fonnd that the internal parts of the head and thighs employed by 

 themselves were as efficacious as those of the body, but the hard parts 

 as usual were destitute of any action. He statesthat this applies also 

 to the officinal species. — Comptes llendus, Dec. 3, 1855, p. 1003. 



UNUSUAL DEARTH OF ALG^ IN 1855. 



Devonport, 19th October 1855. 



My dear Sir, — The present year has been marked by an unusual 

 dearth of Algae on all the Devonshire coasts, and this I have not 

 only had evidence of myself, but it has also been noticed by all my 

 correspondents, who are rather numerous. 



A great many species, which for several successive years I have 

 been in the habit of finding whenever I sought for them, with as 

 much certainty as I should in going into my own garden to cut a 

 cabbage, have altogether disappeared, that is, those plants growing 

 between the extremes of high and low water marks. This unusual 

 occurrence from the ordinary course, after careful consideration, I 

 am inclined to assign to atmospheric influence. 



The early months of the present year, not including those which 

 we usually assign to winter, such as March, April and May, were 

 exceedingly cold, and frosty nights were not unfrequent even in the 

 latter end of May. Our lowest tides here occur at the advent of the 

 new and full moon from about twelve to one o'clock. Plants begin- 

 ning to grow between the tidal limits were thus exposed to a very 

 low temperature during the night ; but a very different result followed 

 at the next low water, occurring at noon, twelve hours after. Here, 

 those plants were subjected to the influence of a vertical sun, and 

 these alternate changes from a high to an extreme low temperature, 

 being followed up during many successive nights and days, had the 

 effect of destroying them altogether. I am the more convinced that 

 my views on this subject are correct, inasmuch as I found all the 

 missing plants by dredging in deep water, and where they could not 

 be affected by changes in the atmosphere. 



Beheve me, dear Sir, very faithfully yours. 



Dr. J. E. Gray. John Cocks. 



Observations on Echini Perforating the Granite of Brittany. 

 By M. Valenciennes. 



The attention of naturahsts has always been awakened by the 

 curious habit of many Mollusca and Zoophyta, of excavating cavities 

 for their habitation in rocks often of great hardness and of very dif- 

 ferent natures. It was at first supposed that these perforating animals 

 only attacked the calcareous rocks, which led several people to think 

 that the erosion required to form the hole was assisted by the action 

 of some acid. It has been admitted of necessity, however, that in 

 particular cases the animals only employed mechanical means, as 

 the Teredos and the Pholades and even the Sipunculi were found to 



