PREPARATION OF THE DIATOMACEiE. 145 



Mr. Norman has furnished us with the following interesting 

 particulars concerning the growth of Campylodisciis costatiis. He 

 says : — In the early part of the spring of 1856 I made a gathering 

 of Diatoms from the Spring ditch, Hull. Although I met with a 

 few frustules of the species named, I did not think it of sufficient 

 interest to boil in acid for mounting ; and the phial containing 

 them was left in the window of my laboratory during the ensuing 

 summer. Some time in the autumn I had occasion to make use 

 of this bottle, when I noticed the surface of the deposit, and the 

 sides of the bottle covered with a dense brown growth of diatoms. 

 On further examination I found an immense colony of Campy- 

 lodisciis^ which gave by preparation some beautifully pure slides. 

 When removing the upper layer, I purposely left a few of the 

 frustules in the bottle, which was placed in the window as before. 

 These have again increased to a great extent, and now they appear 

 to thrive in perfect health. 



Remarkably pure gatherings may be obtained also by Reinicke's 

 method, the principle underlying which is based on the extra- 

 ordinary property possessed by the Diatomaceae of pressing 

 towards the light. A quantity of mud on which the fronds of these 

 little organisms are growing is spread on a common dinner-plate, 

 and upon this is laid a piece of thin muslin, and a little water 

 poured upon the whole, that it may be entirely covered. The 

 plate is now placed in the window of a room where the rays of 

 light fall full upon it, and in the course of a few days the tiny 

 frustules of the Diatoms will begin to creep through the muslin 

 and form a thick growth entirely free from earthy matter. 



This plan can, however, only be carried on with certain species 

 whose movements are free and active, as Pleurosigina^ NitzcJiia^ 

 CoccoJiema, and Navicida. Gerstenberger's plan is so much after 

 this character that it will be needless to repeat it. Successive 

 crops of Diatomace?e may be taken at short intervals, provided the 

 conditions of nature are complied with, by the creation of an 

 artificial spring and winter, which is simply done by allowing the 

 mud on which they are growing to become nearly dry, then pouring 

 fresh water over it, and once more it will be covered with new and 

 luxuriant microscopic life. By some such methods as these appUed 



