1888.] 



MICROSCOPICAL JOURNAL. 



185 



placed between it and the object and nevertheless be entirely invisible. But 

 focusing up and down shows the diflerent levels and proves the spherical 

 character of Protococcus. A single sphere of Protococcus is a cell. It has 

 all the characteristics of a cell. 



It is necessary to say one word regarding a point which cannot be easily 

 proven for Protococcus. It is regarding the nature of the cell-contents. It 

 is believed, v^^ith every reason for confidence, that this substance is composed 

 of two distinct parts — one made up of very minute drops scattered through 

 the mass which makes up the cell-content. This contains the substance 

 which gives the green color to the plant, and is chlorophyl. The remaining 

 substance is protoplasm. This furnishes the reader with a very brief sketch 

 of the facts regarding the structure of the plant in one form, most of which 

 he can easily verify for himself. 



A second set of facts comes out when we notice the modes in which the 

 cells of Protococcus are aggregated. It is the most noticeable thing at first 

 that the plant-cells are in groups of two, four, or more. Examine first several 

 difterent groups of two each. Hardly any two are exactly alike. Fig. 3 

 shows a group of quite common form where there is a very faint indication 

 of constriction, while Fig. 4 shows a very deep constriction between the two 

 cells. In Fig. 5 we find still another case with a deep constriction within, 

 but with a boundary line or cell-wall not constricted outside. Examination 

 of each cell in these groups shows them to contain granular chlorophyl-bear- 

 ing contents and a nucleus. Further study brings to light groups of three or 

 four or more cells. These are called cell-families. Fig. 6 shows a group of 

 three, one large and two small ones. Fig. 7, taken from what seemed at first 

 to be a group of three, proved, on more careful study, to be a group of four. 

 Fig. 8 shows a group of two, with a resemblance to the group of three in Fig. 6. 

 Fig. 9 represents a group of four, all in the same plane ; Fig. 10, a group of 

 tliree in the same plane, but with a fourth in the plane below — really a group 

 of four. Fig. 1 1 is a group of four, but in two sets of twos, and with one 



