304 THE COURTSHIP OF ANIMALS 



niches in the world untenable to creatures of more con- 

 servative habit. That the peculiar " strains " of animal 

 life have turned into backwaters which offer no oppor- 

 tunity or possibility of further advancement seems clear 

 enough, but they are nevertheless interesting and 

 instructive. 



The parthenogenetic Crustacea and the Rotifers afford 

 some good evidence of this adaptability — of the way 

 in which creatures manage to cling to the skirts of life 

 by reason of their power to survive the extremest tests 

 of endurance. And this success has largely been due 

 to some mysterious property of the germ-plasm enabling 

 reproduction to take place through the female line alone, 

 or in some cases with an occasional fillip from the inter- 

 vention of males. Of the many marvellous things that 

 could be related of these creatures but few instances 

 can be cited here. 



The case of the Brine Shrimp {Artemia salina) will 

 afford an exceptionally good illustration because the facts 

 can be tested by anyone who will take the trouble 

 to make a simple experiment for himself. Those 

 anxious to do this should dissolve eight ounces of 

 Tidman's sea-salt in a glass jar containing five pints of 

 water, keeping the mixture well stirred till the salt is 

 dissolved. It should be allowed to stand and be carefully 

 watched. In about three days, with a pocket-lens, or 

 even without, minute white specks will be seen moving 

 with a jerky motion up and down the water. These are 

 larval Brine Shrimps. Now they must be fed '^ Take a 

 piece of lettuce-leaf or any green stuff, and pound it up, 

 or grind it up with a knife-blade on a plate with a little 

 water, till the whole is reduced to the consistency of green 

 paint ; then empty this into the water. This must be 



