4 ELEMENTARY BIOLOGY. [l. 



multiplication is going on, it will be found that they are 

 giving rise to minute buds, which rapidly grow, assume the 

 size of the parent Torula, and eventually become detached; 

 though, generally, not until they have developed other buds, 

 and these yet others. The Torulce thus produced by gem- 

 mation, one from the other, are apt long to adhere together, 

 and thus the heaps and strings mentioned, as ordinarily 

 occurring in yeast, are produced. No Torula arises except 

 as the progeny of another ; but, under certain circumstances, 

 multiplication may take place in another way. The Torula 

 does not throw out a bud, but its protoplasm divides into 

 (usually) four masses, each of them surrounds itself with 

 a cell-wall, and the whole are set free by the dissolution 

 of the cell-wall of the parent. This is multiplication by 

 endogenous division. 



As each of the many millions of Torulce which may thus 

 be produced from one Torula has the same composition as 

 the original progenitor, it follows that a quantity of Protein, 

 Cellulose and Fat proportional to the number of Torulce 

 thus generated, must have been produced in the course of 

 the operation. Now these products have been manufactured 

 by the Torulce out of the substances contained in the fluid 

 in which they float and which constitute their food. 



To prove this it is necessary that this fluid should have 

 a definite composition. Several fluids will answer the pur- 

 pose, but one of the simplest (Pasteur's solution) is the 

 following. 



Water {Hfi). 



SiJgar (C,,H,,OJ. 



Ammonium Tartrate (C^H/NHJP^). 

 Potassium Phosphate (KH^PO^). 

 Calcium Phosphate (CagP^Og). 

 Magnesium Sulphate (MgSOJ. 

 In this fluid the Torulce will grow and multiply. But it 



