RELATIONS AND SURROUNDINGS. 133 



offspring during the course of their development. The 

 care which mammals and birds give to their young is a 

 matter of common observation. It takes the form of 

 special food; of homes as nests, burrows, dens, etc.; and 

 of the personal services of the parents who will often pro- 

 tect the young from its enemies, even at the risk of life. 

 This care of the young reaches its climax in man. The 

 period of helplessness, during which the parents must 

 care for the young, is longest in man. This period of 

 helplessness tends to keep the parents together and fur- 

 nishes the foundation of the home and the family life that 

 has meant so much in human progress. These are the 

 basis of human society; and, in turn, the progress of society 

 and of its standards has made the care and education of 

 the young more complete. In this way the character 

 both of the parents and the offspring is improved. 



147. Practical Exercises. What habits or instincts have the 

 following animals in the matter of caring for the young: flies; 

 the solitary wasps ; the ichneumon fly ; social insects, as the bees and 

 ants; the lobster? Add other instances of parental care that have 

 fallen under your observation. What are "galls" on plants? How 

 many different kinds can you find? 



Compare the condition of the young of the robin, the quail, the 

 blue-jay, and the pigeon, as to maturity at hatching. Do any 

 animals of your acquaintance reproduce more than once in a year? 

 Why is one reproductive period a year a common adaptation ? To 

 what is it an adaptation ? Why do different animals have a different 

 length of life? In general, how long will the life period be in a 

 given species? 



148. Organic Colonies. In some of the lower groups 

 of animals, as the polyps and sponges, in which the re- 

 production by fission or budding is prominent, the newly 

 formed individuals remain for longer or shorter time in 

 association with the parent or w r ith one another (Fig. 27). 

 They often secrete, in common, masses of material which 



