SPERM-EGG INTERACTING SUBSTANCES, II 41 



tozoon are only about 0-5% (Rothschild, 195 1). If the tails of the 

 spermatozoa are concerned with the identification of gradients, 

 the perception system need not be so efficient, as they may be ten 

 times as long as the head. A defect in the experiment depicted in 

 Fig. 8b concerns the behaviour of the spermatozoa immediately 

 after the pipette is inserted into the suspension. If the directions 

 of movement of the spermatozoa are random before the pipette is 



r 



0-9 



"1 

 10 



0-5 

 t (min. ) 



FIG. 8b. — Movements of bracken spermatozoa after insertion of pipette (dia- 

 meter 30 microns), containing 1% sodium L-malate in a 1% agar-tap water 

 gel, into the same sperm suspension as in Fig. 8a. Numbers at the beginning 

 of tracks indicate time in seconds after insertion of pipette, Rothschild (1952). 



inserted, as in Fig. 8a, they should be random immediately after 

 the pipette is put in, before the malate has had time to diffuse 

 significantly into the external medium. Unfortunately, the in- 

 sertion of the pipette into the suspension inevitably causes macro- 

 scopic disturbances in the fluid, so that the earliest phases of the 

 reaction are lost. When someone can devise a method of intro- 

 ducing a source of malate into a suspension without causing such 

 disturbances, we shall learn more about the morphology of chemo- 

 taxis. One interesting question which may be resolved by such a 

 study concerns the morphology of turning. Although there are 

 references in the literature to spermatozoa turning and bending 



