l*>^ JOURNAL OF THE [April, 



CLOSTERIUM ACEROSUM. 



Mr. Balen exhibited cyclosis in Closterium acerosum, using for 

 the purpose a yVth-inch objective. 



PATH OF ELECTRIC SPARK. 



Mr. McAllister exhibited, under a power of sixty diameters, 

 a slide which showed the course taken by an electric spark in 

 traversing a thin film of soot adherent to the glass. Its path is 

 an irregular net-work of mixed sinuose and zigzag lines. Thi<; 

 object is prepared in the following way : — 



A slide, after being smoked over a small gas-jet, is placed 

 centrally between the terminals of an induction coil, and at right 

 angles to their direction. The terminals are held about three- 

 eighths of an inch apart. A strong current is required. 



The President : " A curious effect is produced by passing re- 

 peated charges of electricity from a Holtz machine through two 

 plates of glass, between and in contact with which is a sheet of 

 brass foil. The foil is driven into the glass, and it is retained 

 there permanently." 



OVOID CONCRETIONS ON SHELL OF HEN's EGG. 



Mr. Le Brun showed, under a magnification of twenty-five 

 diameters, a compact group, in a single layer, of a hundred or 

 more ovoid calcareous bodies /// situ on the exterior surface of a 

 piece of the shell of a hen's egg. These bodies are solid, they 

 adhere but slightly to their support and to one another, and their 

 long diameter seldom exceeds one-fortieth of an inch. 



The table of dimensions of the spicules of Heteronieyenia Ry- 

 deri which was prepared by Mr. Hyatt and was published in the 

 February Number of the Journal, page 46, contains a typo- 

 graphical error. Corrected, the table will read as follows : — 



dimensions of SPICULES OF heteromevenia rvderi. 



Largest pointed spicules : average length, lioth of an inch. 



Grappling-hook spicules : average length, lAoths of an inch. 



Short birotulate spicules : length, from i^iVoth to TTJowths of an 

 inch. 



Wheels of short birotulate spicules : average diameter, rti^TT^ths 

 of an inch. 



