40 Life and Death, Heredity and Evolution 



a close relative of amoaba, Difflugia (Figure 11), which 

 is merely an amreba with a shell. In reproduction the two 

 products do not receive half the parental shell ; if they did, 

 as you can readily see, they would indeed not be like the 



Figure 11. Reproduction in Difflugia. After Verworn (1888). 



parent. What happens is this : The shell consists of sand 

 grains, embedded in a hard chitinous substance. As the 

 parent creeps about in its daily life, it takes up sand grains 

 and stores them in the interior of its body. At reproduction 

 the protoplasm of the parent swells and projects from the 

 mouth of its shell (Figure 11, A). This projecting mass 

 takes a form similar to that of the parent (B). The sand 

 grains within the parent body pass out into the projecting 

 mass, come to its surface, and spread over it (C, D). They 

 are embedded in a fluid secretion which now turns hard, so 

 that they form a shell like that of the parent. The two 

 shells are in contact at their mouths (D). Now the common 

 mass of protoplasms divides into two, and the two individuals 

 separate one retaining the old shell; the other with the 

 new one. 



Now you see that it is by no means a simple matter of 



