INDIVIDUAL DIFFERENTIATION AND ADAPTATION. 



Ill 



vices of the parents, who will often at the risk of their own 

 life protect the young from its enemies. Similar care is shown 

 by some insects, especially the social forms, such as bees, ants, 

 and the like. The lobster carries its young on its abdominal 

 appendages for months after hatching. The lower Inverte- 

 brates are practically destitute of these later care-taking 

 instincts. 



It is interesting to notice that animals differ very much in 

 their helplessness at hatching or at birth. The young of the 



FIG. 54. 



FIG. 54. Nestling Marsh Hawks (Circus cyaneus). From Year-Book. Department of 



Agriculture. 



Questions on the figure. What are the nesting and breeding habits 

 of the marsh hawk? Are the young precocial or altricial? 



reptiles, or the duck, or the chicken are relatively well devel- 

 oped at hatching, and are very soon able to run about and 

 feed. The young of the song birds, as the thrushes, swallows, 

 etc., are wholly dependent on the care of the parents for a 

 considerable ti'me. In the herbivorous mammals, as the sheep 

 and cattle, the young have the use of their limbs in a short 



