100 New York State Museum 



death it is by causing asphyxiation. It has been found 

 that corals that can endure a high temperature of the 

 water can endure being buried in mud for a long time 

 without being smothered, while corals that succumb in 

 lower temperatures are smothered during a short burial 

 in mud. Some forms in tropical waters pass through a 

 quiescent phase during the greatest heat of the day and 

 when it is cooler later on become more active. Tropical 

 animals live within about 20°-30°F of their upper death 

 limit and within about 10°F of their temperature of 

 maximum activity. Temperature in general is a very 

 effective barrier to extensive geographical range, but some 

 animals do adapt themselves outside their own range and, 

 exceptionally, even have a wide temperature range. The 

 Horse-shoe Crab (Limulus polyphemus) is a tropical 

 form which has a range from Maine to Yucatan. At its 

 northern limit it survives being frozen in ice and in its 

 southern range, it can endure temperatures up to 112°F. 

 There are certain forms, however, that are confined to 

 the tropics because when they are exposed to temperatures 

 of 50°-54°F they lose the power of movement. 



Of course the effect of varying temperatures is seen in 

 its acutest form in the shallow waters of the tidal zone, 

 and that is why the animals of the tidal area seek shelter 

 under seaweed or boulders or in tide pools, or otherwise 

 protect themselves. The higher portions of the tidal area 

 are most affected. Not only is there exposure to the air 

 and the drying effects of winds, but there is exposure to 

 the sun. The seaweeds of this zone are protected by 

 their gelatinous composition. The type of substratum 

 is very important in considering temperature effect. 

 When the tide is out rock surfaces become greatly 

 heated unless they are covered with a heavy growth 



