as parent, in the act of dividing.- The old individual, after 

 being built up, is completely sacrificed in producing two 

 new individuals. They in their turn do the same thing. 

 We can't have parents and offspring existing side by 

 side in such a case as this, as we see it in the human race; 

 we have merely offspring and nothing more. 



6. Note. There are some other kinds of reproduction 

 found in the one-celled plants and animals. Some of 

 these will be mentioned in other connections, as they will 

 be better understood there. Simple division is found also 

 in some of the higher organisms; but we may fairly say 

 that this simplest of all the methods of reproduction is 

 particularly representative of the simplest organisms. 



CHAPTER FOUR. 

 BUDDING AND BUDS 



1. Resume. In the lowly plants and animals whicli 

 were studied in the last chapter the offspring were 

 formed in the simplest possible way, that is, by merely 

 breaking up the parent into two or more equal parts of 

 the original organism. In this process the children do 

 not have to ask, "What shall we do with our parents?" 

 There are no parents left. Many writers have called 

 attention to the fact that in plants and animals of this 

 sort there is no death of the kind we described in an 

 earlier chapter. The parent sacrifices its individual 

 existence, to be sure; but the substance of which it is 

 made seems almost or quite able to renew its youth as it 

 divides, and thus to preserve itself from old age. Of 

 course these organisms may be killed by accident and 

 by unfavorable conditions. Untold millions of them are 

 destroyed by drouth, by cold, and by attacks of other 

 organisms but probably not from mere old age. 



This method of reproduction is called division or fission. 



2. Another Form of Division. There is another group 

 of single celled plants, called. yeasts, that are important in 

 human industries. They are used in the making of bread, 

 and in brewing beer, and fermenting wines; all this 

 because they have a wonderful power of producing 

 substances that change starches to sugar and break up 

 sugar into alcohol and gases. 



These plants are a little larger than the bacteria, but 

 are still very small and simple. The cells are more plump 

 than the bacteria usually are, varying from elongate to 

 nearly globular. When conditions are good for their 

 life, and one of these cells becomes nearly the mature 

 size, the growing matter within pushes out a little pouch 

 in the wall and some of it flows into this rounded pocket. 

 This is called a bud, and it continues to grow, remaining 

 attached to the old cell. Intimate internal communication 

 is kept up between the cells, somewhat like that between 

 a small room and a larger room in the same house. The 

 bud is plainly the beginning of a young cell like the firs:. 

 As the bud grows larger the connection between it and 

 the mother cell becomes less. In the meantime the first 

 cell may start another bud from another point, or the 

 new cell may itself start a bud. In this way we may get 

 a considerable group of connected cells, some older and 

 some younger. Sooner or later, however, the daughter 

 cells, as they become older, fall apart from the mother 

 cell and thus become independent. How long they 



remain together and how complex the chains become is 

 determined by the species of yeast and by the food, and 

 the conditions of moisture and temperature in which 

 they are growing. 



At other times the yeast cell may divide up the 

 protoplasm on the inside into four small cells, surrounded 

 by the old mother wall. After rest, these finally break 

 loose from the mother cell and live an independent life. 

 Then they grow up to the mature size and begin to 

 reproduce by budding again. This last is not budding. 

 It is more like fission. We shall refer to it ^gain later. 



3. The Essential Nature of Budding. It will be seen 

 from the above that budding is a form of division or 

 reproduction, in which an actual portion of the mother 

 organism forms the beginning. This portion that goes 

 into the young at the start is small, much less than the 

 one-half that goes to the young in division. Much of the 

 nutrition the mother cell takes up after the bud is formed 

 passes on into the young, because of the close connection 

 between the bud and the mother cell. The yeast does 

 not do so much for its bud at the start as is done in 

 fission; but it keeps up its help longer. 



This is the simplest form of budding we find, It is, 

 however, a very good picture of the essential nature of it 

 even in the more complex plants and animals in which 

 we find it. Always in buds some of the very structure of 

 the parent organism grows directly into a small, young 

 offshoot or offspring; and a close, nourishing connection 

 remains by which the young grows at the expense of the 

 parent, a kind of temporary parasite on the parent. 

 Sometimes they separate after a while and live 

 independent lives. In other cases the young remain 

 attached permanently to the old organism until the young 

 themselves are mature and produce other buds. When 

 the whole series of generations remain together 

 permanently like this we call it a colony. 



4. A More Complex Bud: Hydra. This little fresh- 

 water polyp is found widely in the ponds and lakes of 

 North America and is used very commonly in the 

 laboratory work in zoology. We have in it an animal of 

 many cells as simple as the student is likely to find. It is 

 practically a tube open at one end and closed at the other, 

 the wall of which is two cells thick. Near the open end, 

 the wall is pushed out in a number of hollow tentacles, 

 whose cavities are continuous with the cavity of the 

 animal. When the animal has come about to its mature 

 size and is getting an abundance of food, and the other 

 conditions are right, portions of the body wall may 

 pouch outward with the general cavity of the body 

 extending into the pouch. This pouch grows and becomes 

 elongated, taking the usual shape of the body of hydra. 

 After a while it produces tentacles at the outer end, a 

 mouth breaks through, and we soon have a young hydra 

 attached to the mother. It has been formed purely by 

 the budding out of the mother. Food may pass into the 

 mouth either of the mother or the bud and finally get to 

 any part of the inner cavity. The bud grows both by 

 the food the mother captures and by that which it 

 captures for itself. It ultimately becomes free and closes 

 up the tube at the point where it was connected with 

 the mother, and depends for a livelihood on its own 

 exertions. One parent may have several buds of different 

 sizes attached to it at once. It may continue to produce 

 buds throughout the season. This condition is not very 

 different from the yeast, except that this is a many celled 

 animal; whereas the yeast is a single cell, and a plant. 



In many animals of the group to which the hydra 

 belongs, as in the hydroids and the corals of various 

 kinds, the buds do not separate from the parent stock. 

 By clinging together and by having each its own rate of 



