594 THE REPRODUCTIVE FUNCTIONS. 



are formed, and they are generally divided into 

 compartments, the whole being enclosed in a 

 membranous covering, bearing a great resem- 

 blance to the seed-capsules of plants. 



The propagation of living beings by means of 

 ova or seeds, is a process of a totally different 

 class from their multiplication by mere slips or 

 buds ; and the products of the former retain 

 less of the peculiar characters of the individual 

 from which they spring, than those of the latter. 

 This is remarkably exemplified in the case of 

 orchard trees, such as apples and pears ; for all 

 the trees which derive their origin from shoots, or 

 grafts from the same individual, partake of the 

 same properties, and produce a fruit of the same 

 flavour and qualities ; whereas trees of the same 

 species, which grow from seed, have the charac- 

 ters of distinct individuals, and losing all the 

 peculiarities that may have distinguished the 

 parent, revert to the original type of the species 

 to which they belong. Thus from the seeds of 

 the golden pippin, or nonpareil, arise trees bear- 

 ing the common crab apple, which is the natural 

 fruit of the species. By continued graftings, 

 after a long period, the vitality of the particular 

 variety is gradually exhausted, and the grafts no 

 longer bear fruit. This has already happened 

 with regard to the two varieties of apples just 

 mentioned. For these curious facts, and the 

 theory which explains them, we are indebted to 



