CHAPTER XXXIX 



MARINE ZOOLOGY 



It is true that a good many people never have an opportunity to 

 study the conditions present in the ocean or to observe the animals 

 found in its waters and on its beaches. However, with the improved 

 transportation and awakened interest in the subject, there are more 

 and more students of this fascinating subject. Many of the animal 

 forms seem peculiar and spectacular to those of us who reside in- 

 land. With the modern facilities for travel four hundred miles is 

 not remote from the seashore, and every student majoring in biology 

 in colleges or universities within that distance should be given 

 marine experience, first hand. 



The life of the ocean is known as lialohios. Marine animals are 

 affected and limited by many factors which in turn influence their 

 distribution. They are affected by the temperature of the water, 

 the height of the tides, the velocity of currents, salinity of the water, 

 its turbidity, light, pressure, oxygen content, and the nature of the 

 bottom and the shore. The occurrence of the proper food greatly 

 affects the range and abundance of any particular species. Rocky 

 shores harbor the choice food of certain species and muddy lagoons 

 supply other groups. The adaptation and adjustment of the marine 

 animal to the salinity of the water is one of the first considerations. 

 The salt content is effective both quantitatively and qualitatively. 

 If an oyster is taken from the ocean and placed in a fresh-water 

 pond or stream, it absorbs water and swells up excessively. On the 

 other hand, a clam taken from fresh water and placed in the ocean 

 loses water and shrinks. In either case the effects will finally be- 

 come lethal. A few animals, such as lamprey, eels, shad, salmon, 

 and even gar pike and mullet are able to make the transfer from 

 marine to fresh water and vice versa. 



The salinity of the water of the marine habitat is an important 

 and interesting feature to be studied. Along the Texas coast the 

 water is either that of the Gulf of Mexico proper or of the various 

 bays. The analyses* which have been made on the Gulf water out 



♦Reported by Mr. J. G. Burr, Texas Game, Fish, and Oyster Commission. 



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