246 BIOLOGY 



plants, occurring in the lower as well as in the higher. Even 

 in the flowering plants the pollen of a flower is really a mass 

 of spores, although their relation to the growth of the plant is 

 different from that of the spores to the puffball, since they do 

 not grow immediately into a plant like the one that produces 

 them. 



Among the multicellular animals, the production of spores 

 is not found. There is, however, in a few animals a method 

 of reproduction, called parthenogenesis, which in some respects 

 resembles spore formation. The essential differences between 

 reproduction by spores and that by eggs is that a spore 

 grows into a new organism without being united with a 

 sperm, i. e., no fertilization is required (see page 267), while 

 an egg must combine with a sperm in order to be capable of 

 growing into a new organism. Some organisms, however, 

 produce eggs that can grow without fertilization. Among the 

 best-known examples of this is the honey bee. The female 

 bee produces true eggs, some of which unite with sperms, while 

 others develop without such union. The individuals produced 

 from the unfertilized and from the fertilized egg are different, 

 the fertilized eggs producing worker bees or females, and the 

 unfertilized eggs producing males (drones). So far as can be 

 seen the eggs are alike, the only difference between the eggs 

 that produce workers and those that produce males being that 

 one is fertilized and the other not. This phenomenon of the 

 development of eggs without fertilization is called partheno- 

 genesis (Gr. parthenos = virgin -f- genesis = creation) . It re- 

 sembles reproduction by spores only in the fact that it consists 

 of a single cell developing into an adult without the neces- 

 sity of union with a sperm; but the reproductive bodies are 

 identical with eggs, and it is usually described as reproduction 

 by eggs which do not require fertilization. 



Parthenogenesis occurs in a variety of animals with vari- 

 ous complications. Where it occurs it is most common to 

 have such a parthenogenetic reproduction alternate, with more 



