l886.] NEW-YORK MICROSCOPICAL SOCIETY. l66 



the water was, in C and Z>, more energetic than in the others, 

 because of the photochenoical stimulus of the solar light. When 

 the quantity of the diatoms raised is considered, we are im- 

 pressed with the elaborating and assimilating energy of these 

 tiny organisms which use up and yet conserve so large an 

 amount of silica. 



EXPLANATION OF PLATES VI. AND VII. 



The figures on the plate were drawn from a careful study of. 

 a single slide of material from jar C, of the first series. They 

 are magnified 1600 diameters excepting 2^, 2^^ 2", and 8", 

 which are magnified about 800 diameters ; and excepting also 

 Figure 17, the individuals of which are magnified about 350 di- 

 ameters. Only in Figure 2° was I able to detect the median 

 line, and in none could I find the central or the terminal vacu- 

 oles. 



Figure i. This beautiful form was very rare. 



Figure 2. Not rare, and often found as the nucleus of a 

 double nest of layers, as shown in Figures 19, 20, and 21, of 

 the text. 



Figures 3 to 16 inclusive. Figure 3 is a side view of the typi- 

 cal form from which the others are monstrous aberrants. 



Figures 15 and 16. Dumb-bell forms, or wider aberrancies. 



Figure 17. A swarm of embryonal Amphorce, simply a dia- 

 gram. 



Figure 18. Shows one side of the nesting, of which 2^ is the 

 nucleate centre. 



Figures 19, 20, and 21, Nests, of which Figure 2 is the 

 nucleus. 



All these figures are described more fully in the text, where 

 their exact magnitudes are also given. 



I am indebted to my friend. Dr. Alfred C. Stokes, the infusor- 

 ist, for the measurements given in this paper, and to his facile 

 pencil for the drawings. The measurements were made with a 

 Rogers micrometer eye-piece and a Fasoldt stage-plate, and the 

 objective used was a Herbert R. Spencer homogeneous-immer- 

 sion TO of N. A. 1.35. 



A NOTE. 



Under date April 6th, 1886, Dr. Alfred C. Stokes wrote 



