472 LIFE-HISTORIES 



life." Its exact chemical constitution is not known, nor 

 does it seem likely that it ever can be known ; for to analyze a 

 sample of protoplasm chemically is to kill it, and dead pro- 

 toplasm surely differs in important waj's from protoplasm 

 alive. Moreover, through the many complicated reactions 

 going on within, an}' active mass of protoplasm is doubtless 

 continually changing its composition. One of the products 

 of the activity of the protoplasm of a tint-ball is the blue 

 substance above mentioned; another product is the chloro- 

 phyll by •means of which it is al)le to make food in the sun- 

 light like any other plant containing leaf-green. Still another 

 product is the gelatinous material forming the enveld^e by 

 which the little mass of protoplasm is surrounded. Chemical 

 tests would show that this envelope consists of a kind of 

 cellulose. The food which the protoplasm is able to make 

 from the substances it absorbs through its cellulose shell 

 from the surrounding water, is used by the plant as material 

 for growth. That is to say, it uses the food to make new 

 protoplasm out of which come new coloring matters, new 

 cellulose, and other organic products. As the growth of the 

 sphere is mainly in one direction it becomes elongated into 

 an (>llipsoitl as shown at B. Meanwhile, the denser central 

 part of the protoplasm has similarly elongated and finally 

 divided into cUstinct halves. These halves move toward 

 the ends of the ellipsoitl, thus becoming surrounded on all 

 sides by the thinner protoplasm. Soon there appears in the 

 ellipsoid a plane of separation extending through the center 

 at right angles to the long axis; then each of the portions of 

 protoplasm on either side of this plane becomes larger and 

 rounder, and each along the plane of separation builds a 

 layer of cellulose which presently appears as a cross ])arti- 

 tion (C). At last, as a result of further growth and rounding 

 we have two distinct spherules of protoplasm, each with 

 its central, denser part and each surrounded by its own 

 cellulose envelope esscntiallj^ like the original tint-ljall. Thus 

 through growth and division one i)lant has become two. 

 These plants may remain attached to one another and each 

 of them may divide again and repeat the process a number 

 of times without separating. The result then is a colony in 



