12 THE BEGINNINGS OF LIFE. 



vast number of cells of globular elliptical form moving in fluid. 

 These bodies are the yeast plant or Saccharomyces which 

 produces the frothy fermentation of the yeast. They are 

 unicellular plants, minute points of protoplasm surrounded with 

 a very thin delicate cell wall, and by employing special methods 

 of investigation a nucleus can be detected. The mode of repro- 

 duction in the yeast plant is peculiar. A small bud-like pro- 

 tuberance of protoplasm forms at the surface of the cell pushing 

 ^ut the cell wall before it. It enlarges, and at last a partition 

 forms between it and the mother cell. Ultimately it separates, 

 but before doing so may itself develop a bud, so that sometimes 

 chains or groups of cells are formed. 



Placing the yeast aside we take from one of our collecting 

 flasks a drop of water obtained from a pond after a thunder- 

 shower and which attracted attention by its uniform green tinge. 

 On examination under the microscope we are surprised to find 

 that the green tinge is due to a multitude of ovoid cells filled 

 with bright green colouring matter interspersed with occasional 

 spots of red. Each of these ovoid bodies is a little plant which 

 consists of but a single cell and which has received the alarming 

 name of Protococcus pluvialis — a name, however, which ceases to 

 be a bugbear when we perceive that protococcus is simply a 

 compound of two Greek words meaning primary grain or 

 granule, and that pluvialis is a Latin adjective pointing to the 

 fact that you are likely to find the little plant in your tanks after 

 a heavy shower. Continuing your examination you see that the 

 ovoid cells have a thick colourless cell wall enclosing the 

 protoplasm in which we observe the nucleus and the bright 

 green colouring matter known as Chlorophyll, which we see in 

 the leaves of plants. The little cells are quite motionless, but 

 keep them under examination patiently and notice what happens. 

 The protoplasm of the cell divides into two, and the process is 

 soon afterwards repeated, so that there result from four to as 

 many as sixteen daughter cells contained within the cell wall of the 

 mother cell. The enclosed cells assume a pear-like form, the cell 

 wall bursts and the daughter cells are set free. As soon as this 

 happens we are surprised to see that the free cells begin to swim 

 actively about, and by careful treatment of one of them we are 

 able to discern that the movement is caused by two long delicate 

 filaments or processes, which have developed at the pointed end. 



