166 JESSIE A. SALLITT. 



from '0035 mm. to "006 mm. in diameter. Eacli corpuscle 

 consists of two parts: 1, a ball of clear protaplasm; 2, an 

 investing cup-like layer of chlorophyll-containing protaplasm 

 (fig. 1). For convenience I call the chlorophyll-containing 

 layer chloroplasm. The chloroplasm is of a bright light green 

 colour. It is bleached by alcohol, and is then seen to consist 

 of granular protoplasm. With iodine the whole corpuscle is 

 stained brown j the chloroplasm stains more deeply than the 

 central protoplasmic mass. 



Division of the corpuscles.— Simple division (fig. 2) 

 begins by cleavage of the chloroplasm at right angles to the 

 margin of the cup. The division gradually extends down to 

 the base of the cup, and at the same time the chloroplasm fre- 

 quently grows upwards so as to enclose more completely the 

 central ball. This is followed by cleavage of the central proto- 

 plasm which completes the division. In many cases division is 

 preceded by elongation of the corpuscles in a direction parallel 

 to the mouth of the cup, and the cleavage of the clear proto- 

 plasm is coincident with that of the chloroplasm (fig. 2, a) , 



Division in three parts occurs by a second division in one 

 half of a dividing corpuscle (fig. 3). The fresh cleavage line 

 extends as in the first case down to the chlorophyll pole of the 

 corpuscle. 



Division in four parts only differs from that in three by the 

 occurrence of a second division in each half of the dividing 

 corpuscle. The chloroplasm grows up to surround the proto- 

 plasmic ball before division is effected in the latter. In conse- 

 quence of this, when the division is complete in the chloroplasm, 

 the corpuscle appears to be dividing by simultaneous horizontal 

 and vertical cleavage (fig. 4). An earlier stage shows that 

 both divisions are vertical. 



The newly formed corpuscles are usually small and somewhat 

 angular (fig. 5). They become more spherical as they grow 

 larger. 



Stentor polymorph us (figs. 6 — 13). — The corpuscles 

 closely resemble in form, mode of division and intensity of colour, 

 the corpuscles of Paramecium bursaria. They are slightly 



