MULTIPLICATION AND DEVELOPMENT 61 



exactly alike the new individual, made up of parts of 

 each of them, will differ slightly from both. Nature 

 seems intent on making every new individual differ slightly 

 from the individual which precedes it. And the method 

 of multiplication which Nature has adopted to produce 

 the result is the method which we have seen exhibited in 

 its simplest form in the case of Paramcechnn the method 

 of having two individuals take part in the production of 

 a new one. 



The development of the new Paramoccia is a little more 

 complex than that of Amccba. Not only must the new 

 Paramccciinn grow to the size of the original one, but it 

 must develop those slight, but apparent, modifications of 

 the parts of its body which we can recognize in the full- 

 grown, fully developed Parainoccium individual. A new 

 mouth-opening must develop on the new individual 

 formed of the hinder half of the original Paramccchuu and 

 new cilia must be developed. Thus there is a slight 

 advance in complexity of development, just as there is in 

 complexity of structure in Paramachnn as compared with 

 Amccba. In the many-celled animals this complexity of 

 development is carried to an extreme. 



Birth and hatching. When a young animal is born 

 alive, it usually resembles in appearance and structure the 

 parent, although of course it is much smaller, and requires 

 always a certain time to complete its development and 

 become mature. A young kangaroo or opossum is 

 carried for some time after its birth in an external pouch 

 on the mother's body and is a very helpless animal. A 

 young kitten is born with eyes not yet opened and must 

 be fed by the mother for several weeks. On the other 

 hand young Rocky Mountain sheep are able to run about 

 swiftly within a few hours after birth. 



