I7<> EDWIN J. COIIN. 



an indication of death only if accompanied by some other obser- 

 vation such as the dissolution of the protoplasm that follows the 

 death of spermatozoa. This is necessary, since a decrease in the 

 activity of spermatozoa may also decrease their fertilizing power. 

 But sperm that are non-motile can be reactivated, and until 

 reactivation is no longer possible, sperm can not be considered 

 dead. 



The rate of movement of spermatozoa cannot, however, be 

 observed with any degree of accuracy. While it is not difficult 

 to distinguish between a very motile, a fairly motile and a non- 

 motile sperm suspension, more delicate fluctuations in sperma- 

 tozoon activity cannot easily be observed. As in other cells a 

 delicate indicator of the degree of activity is afforded by the 

 measurement of the oxygen consumption (Loeb and Wasteneys, 

 1912; Warburg, 1910) the heat production (Meyerhoff, 1911) or 

 the carbon dioxide production of a sperm suspension. The car- 

 bon dioxide production of sperm suspensions of different concen- 

 tration has been measured. 



The activity of spermatozoa, as will presently appear, is effected 

 by changes in either the temperature, the osmotic pressure or 

 the hydrogen ion concentration of sea water. Since even the 

 carbon dioxide produced by spermatozoa is sufficient appre- 

 ciably to change the hydrogen ion concentration of a o 005 per 

 cent, suspension, since the activity of spermatozoa is a function 

 ot the hydrogen ion concentration, and since the fertilizing power 

 of a sperm suspension is related to the activity of the sperma- 

 tozoa, the careful control of the environment becomes a necessity. 



SEA WATER AS ENVIRONMENT. 



The environment of the spermatozoa of the sea urchin is sea 

 water. A variable in sea water that is known to effect the 

 activity of spermatozoa is the hydrogen ion concentration. The 

 concentration by weight of hydrogen ions in sea water is approxi- 

 mately o.oooooooi N or i X io~ 8 N (Palitzsch, Sven, 1912). In a 

 neutral solution there are, by definition, as many hydrogen as 

 hydroxyl ions. The concentration of hydrogen ions in a neu- 

 tral solution is i X io~ 7 N or 10 X io~ 8 N. There are there- 

 fore in the neighborhood of ten times as many hydrogen ions 



