136 THE WONDER OF LIFE 



found a red water-bear and a red Eotifer {Callidina scar- 

 latina) among snow on Monte Rosa at a Leight of 11,138 

 feet, which is another good instance of the insurgence of life. 



Brine Shrimps. — The pretty httle brine-shrimp 

 {Artemia salina) that used to occur in British salterns, and 

 has a widespread distribution from the Great Salt Lake 

 of Utah to Central Asia, is famous in several ways, and 

 notably because it can hve in water with as much as 27 

 per cent, of dissolved salts, yet occurs, though rarely, in fresh 

 water. It is usually about haK an inch long and has a pale 

 reddish colour, due, as Sir Ray Lankester first showed, to 

 the presence in the body fluids of haemoglobin — the char- 

 acteristic vertebrate blood pigment which is somewhat 

 rare in Invertebrates. In some places the colonies seem 

 to be altogether female, and parthenogenesis obtains, the 

 eggs developing without being fertilized. In other locahties 

 males are common and reproduction takes place by means 

 of fertihzed eggs. Sometimes the Brine Shrimp is vivi- 

 parous, the eggs hatching within the mother's brood-sac and 

 giving rise to microscopic larvae (Nauphi) with three pairs of 

 limbs and an unpaired eye. Variable in its reproduction, 

 the Brine-Shrimp is variable also in its form, especially as 

 regards the end-lobes of the tail and the bristles they bear. 

 Perhaps this is correlated with the chemical diversity of 

 the habitats frequented. The eggs can survive being dried 

 and may be blown about by the wind or carried on the feet 

 of birds from one salt pond to another. We have already 

 referred to their occurrence in Tidman's Sea-Salt. 



A Hazardous Home. — One knows the narrow shelves 

 high up on the Alps, which, for part of the year at least, 

 are the homes of men, women, and children ; one knows 

 the narrow ledges on the precipitous Bird-bergs where 



