164 A. H. REGINALD BDLLKR. 



One may not infrequently see a spermatozoon attaclied 

 lengthwise to tlie nnder surface of a cover-glass move in a 

 circle by means of a series of jerks, between every two of 

 which it comes to rest. In these cases one often clearly sees 

 the whole spermatozoon and not merely the head. One may 

 then observe that the tail is curved and that circulation 

 takes place in the direction of the curve. Fig. 4 represents 

 what apparently happens, the spermatozoon being drawn in 

 the resting stages. It is quite evident that rotation does not 

 take place upon the tip of the tail, but that the whole tail at 

 each jerk takes up a new position. 



Observations upon a few (possibly nearly pxliausted or 

 immature) spermatozoa lying just beneath, and apparentl^^ 

 attached to the sui'face of the cover-glass, showed that, as 

 in the case of insects, the head does not alter its shape and 

 is not concerned in locomotion, and thnt waves of movement 

 arise in the fore-part of the tail and proceed toward its end. 

 The driving force thus appears to lie close beneath the 

 head. 



With regard to the manner in which the rapid and con- 

 tinuous revolutions upon surfaces take place, if isolated 

 observations upon a number of slowly moving spermatozoa 

 will allow one to draw conclusions, perhaps the explanation 

 may be as follows : — When a spermatozoon revolving in a 

 spiral comes into accidental contact with a glass surface by 

 the tail, at least the hinder end of this is unable to leave the 

 glass owing to its adhesiveness, but can more or less easily be 

 dragged along it. The fore part of the tail, by means of its 

 automatic movement, causes the head and itself to make 

 constant excursions to and from the glass surface. The 

 tail is probably slightly curved, and the direction of motion 

 of the spermatozoon is thus constrained to be circular. 

 The head must frequently come in contact with the glass 

 by its tip, which is specially adhesive and liable to l)ecome 

 fixed in one place. Ballowitz holds that the circles upon 

 surfaces for insects arc probably simply the modified spiral 

 turns of the free-swimming spermatozoa. This view, which 



