ANIMAL LIFE-HISTORIES— PROTECTION OF 

 EGGS AND YOUNG— ANIMAL DWELLINGS 



CHAPTER LV 



LIFE-HISTORIES, &c., OF BACKBONELESS ANIMALS 



(Invertebrata) 



To do full justice to the important question of Life- Histories, 

 and related topics, a complete volume of this work would not afford 

 too much scope. But, as full treatment of the kind would lead 

 to undue limitation of the space to be devoted to equally interest- 

 ing subjects, it is proposed to deal with only a small number of 

 cases, selected with reference to general principles. Protection 

 of Eggs and Young will include passive protection by mechanical 

 devices, and also active protection on the part of parents. And 

 it may be remarked that Animal Dwellings commonly owe their 

 importance to the fact that they are employed as nurseries, and 

 some of them are constructed solely for this purpose. Certain 

 life-histories have already been dealt with more or less fully in 

 earlier sections, and others will receive treatment in the later parts 

 of this work, under such headings as Instinct and Intelligence, 

 Parasitism, &c. 



LIFE-HISTORIES, &c., OF ZOOPHYTES (Ccelenterata) 



A great many of the familiar forms known as Jelly-Fishes are 

 simply stages in the life-history of fixed colonial animals that have 

 been produced by the budding of a single individual. A typical 

 case is represented in fig. 867. We have here a simple illustration 

 of the phenomenon known as alternation of generations. In other 

 words the life-cycle does not consist of the continuous gradual 

 growth of an individual from a bud, fission-product, or ^'g'g, but 

 comprises at least two stages or generations, one propagating by 



