NIPHER — NEW FORM OF LECTURE GALVANOMETER. 2S7 



a few of the winged females issue as late even as the latter part of 

 October, some few also of the later produced impregnated eggs 

 may pass the winter unhatched ; if so, they may be considered ex- 

 ceptions to the rule. In the same way, a few of the more common 

 eggs from the agamous ? may be exceptionally found on the 

 roots in winter, though as a rule only the hibernal larva is found. 



In conclusion, I would state that this year's studies of both 

 vastatrix and Rilcyi confirm me in the opinion, elsewhere main- 

 tained (7th Rep., p. 91), that the term "pupa," as applied to the 

 sexed eggs by Lichtenstein, is quite unwarranted, and that the 

 egg-covering — thin and plastic though it be — can in no sense be 

 likened to a cocoon, and still less to a " silken cover."* The fact 

 of its shrivelling up makes it none the less an egg-shell, for this 

 shrivelling process occurs in all eggs with very delicate and plas- 

 tic covering, and may, indeed, be witnessed in the gall-inhabiting 

 form of vastatrix, though no one has thought of questioning the 

 ovarian nature of the eggs found in those galls. 



My sincere thanks are due to Miss M. E. Murtfeldt, who has 

 carefully carried on observations for me during my necessary 

 absence. Without her patient watching and persevering efforts, 

 my endeavors must have measurably failed of results. 



On a New Form of Lecture Galvanometer. 



Bv Francis E. Nipher, Professor of Physics in Washington University. 

 [Read Oct. iS, 1875.] 



In the September number of the American jfo?irnal of Sci- 

 ence, Professor George F. Barker has described a lecture gal- 

 vanometer which possesses marked advantages over any other 

 instrument heretofore described. 



Barker's galvanometer is an attachment to the vertical lantern 

 manufactured by Geo. Wale & Co. of Hoboken, N. J., and its 

 construction may be understood from the following brief de- 

 scription : 



The upper needle of an astatic system plays over the horizon, 

 tal condensing lens of the lantern, its deflections being shown by 



* Stetleiner Ent. Zeitung, 1875. p. 35S. 



