THE STORY OF THE BACTERIA. 



cell a creature which is composed of a single 

 cell and all the activities which I have men- 

 tioned as characteristic of living things are 

 exhibited in it. It is a perfectly independent 

 being, doing every thing for itself, and doing 

 nothing particularly well, except, perhaps, 

 performing the function of reproduction, 

 which it does with such ease and nonchalance 

 as leaves little to be desired. The young 

 which it produces are just like the parent, 

 single cells, and their very first post-natal act 

 may be to give birth to other amcebas. 



Now let us advance a step in the scale of 

 being, to an animal composed of several cells. 

 There is a little creature, one of the group of 

 sponges, called olynthus. Let us start with 

 the ovum of the animal, which is a single cell, 

 not very unlike the amceba in appearance. 

 Under suitable conditions, this cell divides as 

 the amoeba does, and two cells are produced, 

 just exactly alike. They do not separate, 

 however, as do the amcebas, to become inde- 

 pendent individuals, but remain fastened 

 together ; then each cell divides again, and 

 these still further, until we have a little mass 



