SPERM-EGG INTERACTING SUBSTANCES, II 43 



morphology of the phenomenon, we are driven to postulate the 

 existence of sperm sense organs not fundamentally different from 

 those which cause a moth to fly towards a light. Another example 

 of the 'repulsive effect' of an increase in speed is a sealed test-tube 

 containing a gas, one end of which is heated. The highest con- 

 centration of gas molecules will be found at the cold end of the 

 test-tube, where the molecules will be moving more slowly than 

 at the hot end. 



Chemistry of chetnotaxis. This subject has been most sys- 

 tematically examined in the ferns, horse-tails and quillworts; the 



TABLE 6 

 Effect of certain organic acids on the spermatozoa of Equisetum 



arvense 



principal results are summarised in Table 9 at the end of this 

 chapter. In this table, ' + ' means 'attracts', 'o' means 'does not 

 attract', and '— ' means 'no information'. The organic anion is 

 responsible for the attraction, because in those cases where it 

 occurs, the same effects are obtained, for example, with the sodium 

 salt. The case of Equisetum arvense Linn, is in some respects the 

 simplest, from the point of view of the specificity of the perception 

 mechanism. The relevant information is extracted in Table 6, from 

 which the following conclusions can be drawn : to attract the sperm 

 oi Equisetum, Xho. suh?,t2inQ,Q must (i), be a 4-carbon dicarboxylic 

 acid; (2), have an OH group on C^ or C^ (Geneva system of 



the same defects as Klinokinesis with Adaptation so far as sperm chemotaxis is 

 concerned. A few observations about the possibility of Orthokinesis with 

 Adaptation will be found in a paper by Rothschild (1952). 



