.■1. E. Verrill on Ascidiam from New England. 443 



n1 the formation of a jet Instead of this, several 



iiiclies of the cloth were covered with a bright glow, 



i:it resembling that on the positive ball, but, unlike that, 



ly made up of innumerable minute points or patches of 



:^\ nig a peculiar swarming motion, Hke that described 



' i in his researches upon the negative discharge as seen 



;i:i'i'r the microscope. When the paper grating was placed 



lA-iweeu the poles, the image on the positive was not readily 



obtained with distinctness, but was generally much smaller 



than when the negative pole was not thus covered. 



A similar eifect, but much more brilliant, was produced when, 

 tbe poles being separated nine or ten inches, the hand w-as 

 placed upon the negative, and the arm was approached to the 

 positive pole. The woolen sleeve exhibited a bright glow cov- 

 ering a large area, and appearing like a strongly phosphores- 

 cent powder sifted profusely upon it When this was a|)- 

 proached so near that the interval was only an incli and one 

 naif or an inch, the positive glow became much more intense, 

 and took a delicate purplish tinge, and the whole space between 

 the two was filled with a very faint auroral light, which 

 appeared, unlike other forms of the discharge, to be perfectly 

 continuous and steady. The dark discharge under these cir- 

 cumstances was evidently so much intensified as to become 

 '""imous and visible. 



Willianij 



istown, Mass., AprU 2 



AfiT. LXY.— Brief Contributions to Zoology from the Museum of 

 fale College. No. XIV. —Descriptions of new and imperfectly/ 

 known Ascidians from New England; by A. E. Yebrill. 



[Contmued from page 294.] 



Family, Didemnid^ 

 In this family we include, together with the typical genera, 

 ^ptocknum and its allies, which have been separated as a dis- 

 nn i 1^°?'^^ {Leptoclinidce) by Prof Gill.* There appears to be 

 „, aetimte ground for such a distinction. The genera JDidem- 

 P^ and Lepioclinum are verv closely aUied, and scarcely 

 distinguishable so far as the structure of" the individual zodids 

 ^concerned, the difference being chiefly in the mode of aggre- 

 s*"on. Such differences are generally of too little importance 

 ^ong compound animals to form the basis of family distinc- 

 ^-^^°^,^^|ess accompanied by important differences in the mdi- 



