FRRTILTSATION OK THE ECAi^ OF ANIMALS. 157 



were killed or broui^ht to rest. Tliey were thus not repelled 

 by coucentrated sea-water. 



When to one end of: a large oval drop containing sperma- 

 tozoa some crystals of sodium chloride or potassium nitrate 

 were added, similar results were obtained. The sperma- 

 tozoa allowed themselves to be surprised by the advancing 

 salt and were accordingly killed. 



The drop experiments were, then, not more successful than 

 those with capillary tubes. No evidence of chemotactic 

 reaction could be obtained by either method. 



Massart^ found by experiment that tAvo species of 

 Spirillum A and C, the flagellate Heteromita rostrata 

 and two species of Ciliata fled from solutions both more or 

 less concentrated than sea-water, i. e. they always sought a 

 zone with the concentration equal to their normal medium. 

 Oxytricha gibba also fled from solutions more highly 

 concentrated than sea-water, but failed to avoid those less 

 concentrated. In the case of his Spirillum B he obtained 

 an organism which did not flee from solutions either more or 

 less concentrated than sea-water, and which suifered in the 

 experiments accordingly. Both the drop and capillary tube 

 experiments described above appear to indicate that the sper- 

 matozoa of the Echinoidea, like Massart's Spirillum B, are 

 quite insensible to tonotactic stimuli. 



Finally, I attempted to determine whether the spermatozoa 

 are attracted or repelled by oxygen. Fresh spermatozoa 

 were removed from a testis and placed fairly thickly together 

 in a drop, so that the latter was very slightly milky. A cover- 

 glass 0'15 mm. thick and 18 mm. square, supported on pieces 

 of another cover-glass also 0-15 mm. thick, was then placed 

 upon the drop in such fashion as to include a small bubble 

 of air near the middle. Under these circumstances one sees 

 neither atti-actiou nor repulsion from the bubble, even when 

 the experiment has continued some time and when the 

 oxygen supply must be getting low. 



When, however, the drop is made very milky by spreading a 

 ' Massurt, loc. cif., pp. 151 — loi. 



