1885.] 



MICKOSCOPICAL JOURNAL. 



139 



strips connected with the battery wires 

 and terminating in brushes of platinum 

 wire of extreme tenuity. The electric 

 fluid, in its passage from one terminal to 

 the other, formed a very attractive object 

 under the microscope. One of the slides 

 was used to show the effect on the electric 

 spark of interposing films of soot of dif- 

 ferent thicknesses. In its passage through 

 these the current was deflected into mean- 

 dering lines, around which scintillated 

 showers of sparks. The particles of soot 

 could be seen arranging themselves in 

 symmetrical groupings around the ter- 

 minals. In conclusion, Mr. Banks an- 

 nounced that he had sent for, and would 

 soon be able to exhibit, the Stokes-Watson 

 apparatus for showing under the micro- 

 scope the combustion of various metals in 

 the electric arc. 



— There is a law of adaptation in na- 

 ture which the naturalist, in whatever 

 field he may be occupied, finds exempli- 

 fied in many ways. Dr. W. Breitenbach, 

 describing the small crustaceans which 

 have their home on the floating islands 

 of sea-weed of the Sargasso Sea, gives the 

 following interesting account of them in 

 Popular Science Monthly : — 



' The adaptation of the innumerable tints 

 to every grade of change in the color of 

 the sea-weed is really marvellous. The 

 younger, lighter green crustaceans are 

 always to be found on the young, verdant 

 fronds of the plant, while the older parts 

 of the weed are inhabited by older, brown 

 animals. The older stems are often in- 

 crusted with the white shells of bryozoa, 

 and corresponding with these we are sure 

 to find white spots on the brown armor of 

 the crabs. The legs of the animals are 

 frequently of an olive green ground with 

 brownish spots, deceptively like the slen- 

 der sea-weed leaves that are just begin- 

 ning to turn brown. If one will, as I did, 

 pull one of the large plants upon the deck, 

 leave it in a cask of sea-water for an hour 

 or two, and then look through it for crabs 

 without disturbing it, he will find it very 

 hard to discover three or four of the ani- 

 mals, although he may be sure there are 

 a quarter of a hundred of them there ; 

 and, if he gives the mass a lively shake, 

 he will find a curious assemblage of the 

 most varied sorts tumbling off the bush, 

 whose behavior will go far to verify Wag- 

 ner's view ; for, if they are allowed the 

 opportunity, they will all swim back to 

 the sea-weed, and each will seek a part 

 of the plant most like it in color. I tried 

 the experiment forty or fifty times, and 



never saw a little green crab settle on a 

 dark-brown stem. The crustaceans keep 

 to their color, and the brown ones will, 

 with amazing speed, dart through the 

 thick net-work of stems and leaves, to the 

 darkest spot they can find, where they 

 quickly escape observation.' 



— The Portland (Me.) Society of Natu- 

 ral History gave a microscopical exhibi- 

 tion on the evening of April 27th, a pro- 

 gramme of which we are pleased to ac- 

 knowledge. There are twenty-six micro- 

 scopes on the list, and two objects for 

 each. The society was incorporated in 

 1850, and is therefore among the older 

 scientific organizations of the country. 



CORRESPONDENCE. 



Volvox Globator. 



To THE Editor : — After searching 

 nearly every pond and pool in the vicinity 

 of Washington for Vohtox, I found 

 plenty and fine specimens in the heart 

 of the city. During a drenching rain to- 

 day, I made a gathering from the pond 

 spanned by the bridge running from Cen- 

 ter Market to Pennsylvania Avenue, and 

 among other strange specimens was the 

 long-sought Volvox. I believe I am the 

 first to find Volvox in the District. 



H. A. DoBSON, M. D. 



May 29TH, 1885. 



NOTICES OF BOOKS. 



First Annual Report of the Bureau of Ani- 

 mal Industry for the year 1 884. Wash- 

 ington : Government Printing Office. 

 (8vo, pp. 512.) 



This valuable report is a detailed ac- 

 count of the investigations and general 

 work under the direction of D. E. Salmon, 

 D.V.M., chief of the Bureau. It contains 

 so much that is of importance and interest 

 that we shall not attempt a review in this 

 place. The outbreak of pleuro-pneumo- 

 nia in the West has afforded an opportu- 

 nity to study some features of this disease, 

 and especially to establish beyond ques- 

 tion the fact of its contagious nature. A 

 brief review of the evidence concerning 

 the cause of the disease known as swine- 

 plague, which Dr. Salmon's investigations 

 have shown to be a micrococcus, is given, 

 illustrated by two photo-micrographs. An 

 article on the Gape Disease of Fowls, 

 by M. P. Meguin, is translated by Dr. 

 Theobald Smith, accompanied by a plate 



