680 RECORD OF CURRENT RESEARCHES RELATING TO 



filaments were also observed, wliicli presented a resemblance to 



Oscillatoria labyrinthiformis. 



Polycystis aeruginosa, a cause of the Red Colour of Drinking- 

 water,*— In a garden-ditcb in a village in West Prussia, from tbe 

 month of June till the end of August, 1877, and again in 1878, the 

 water assumed on the surface during the day a burgundy or reddish- 

 brown colour, changing at sunset to green. This has been determined 

 by Magnus of Berlin to be caused by a superficial growth of the Alga 

 Polycystis ceruginosa. 



Rain of Blood, t — In the year 1878, J. Brun noticed on the 

 sacred mountain Djebel-Sekra, near the sacred city of Ouessin, in 

 Morocco, a so-called " rain of blood," which he found to result from 

 a quantity of minute shining flakes, which adhered closely to the rocks, 

 and presented an extraordinary resemblance to drops of blood. These 

 were found to be a young, undeveloped condition of Protococcus fluvi- 

 atilis, mixed with organic remains and extremely fine sand. The 

 explanation suggested was that they were brought by a strong south- 

 west wind from the Sahara, where the Protococcus is assumed to be 

 extremely abundant. 



Endoehrome of Diatomacese.l — M. Petit has compiled a very 

 useful account of all that is at present known respecting the colouring 

 matter of the cell-contents of the Diatomaceas, a full translation of 

 which is appended : — 



" Hitherto, so far as I know, there has been published no general 

 work on the endoehrome of the Diatomacese. There is, however, no 

 lack of papers, but they are scattered through the numerous works 

 which have appeared in England, America, Germany, &c., during the 

 last fifteen years. I am going to attempt to collect the data which we 

 possess on this subject, adding some of my own personal observations. 

 I have considered that, for clearness, it is preferable to put aside 

 the erroneous opinions which inevitably j)revailed in the early days 

 of the study of this very interesting group of unicellular AlgaB, and 

 only to consider those which have been recognized as correct by the 

 greatest number of observers. 



1. Natureofthe Endoehrome. — Every one knows that the Diatomacese 

 are distinguished from other unicellular Algae by their envelope, which 

 is formed of two siliceous valves which fit one in the other, and also 

 by their colour, varying from pale yellow to dark broicn. They owe 

 this particular tint to a coloured plasma, which affects (in a manner 

 invariable for every species in a healthy state), sometimes the form of 

 lamince, sometimes that of granules. 



This coloured plasma, called by Kutzing § gonimic substance 

 (^substance gonimique) is now known under the name of endoehrome, 



* ' Ber. Versamml. Westpreuss. Bot. Zool. Ver. Marienwerder.' See ' Bot. 

 Centralbl.,' i. (1880) p. 195. 



t ' Bull. Soc. Belg. Micr.,' v. (1880) p. 55. 



j ' Brebissonia,' ii. (1879-80) p. 81. 



!^ ' Die Kieselschiiligcn Bacillarieu oder Diutomeen.' 



