SPERMATOGENESIS— INSEMINATION 179 



of the ovum.i Dewitz's observations were subsequently con- 

 firmed by Ballowitz.^ 



Counter-clockwise rotation upon surfaces was first recorded 

 for tbe spermatozoa of Echinoderms by Dungern,^ wbo dis- 

 covered the phenomenon in Sphcerechinus and Arbacia. About 

 the same time BuUer,* who has described the manner of rotation 

 more fully, observed its occurrence in the sperms of various 

 other Echinoderms, and particularly in those of Echinus : 

 " When a spermatozoon comes in contact with a glass surface, 

 unless it becomes immediately fixed to the glass [it] begins to 

 make characteristic circular revolutions upon it. If the cover- 

 glass be supported by pieces of another cover-glass, and the 

 upper surface of the drop in contact with it be carefully focussed, 

 it is seen that all the spermatozoa which are not attached by 

 their heads, but are moving there, are revolving from the 

 observer's point of view in clock-wise direction. If the lower 

 surface of the drop in contact with the slide be examined, a 

 reverse rotation — the counter-clockwise — is seen to be the rule. 

 In both cases, therefore, if the surfaces be regarded from the 

 point of view of the spermatozoa, the rotation is always in one 

 direction — namely, the counter-clockwise." 



The head is the only visible part of the rotating spermatozoon. 

 This moves rapidly round in a circle, which in the case of 

 Echinus is sUghtly less than 0'05 millimetres (or the length of 

 a spermatozoon) in diameter. A normally rotating sperm of 

 Sphcerechinus was observed to make 109 circles around one 

 point in ninety seconds. The rate of movement of the head is 

 calculated to be about 0-12 milhmetres per second, or 7-2 milli- 

 metres per minute. 



The characteristic rotation may Hkewise take place upon 

 surfaces which are bounded by air (instead of glass), and it has 

 been observed also upon the outer surface of the gelatinous 

 layer of the ova of Echinus. BuUer concludes, therefore, that 

 the nature of the surface is not an important factor in the process. 



' Verworn, General Physiology, Lee's Translation from the second German 

 Edition, London, 1899. 



' Ballowitz, loc. cit. 



^ Dungern, "Die Ursachen der Specietat bei der Befruchtung," Zentralbl. 

 f. Physiol,, vol. xv., 1901. 



■* Dungern, loc cit. 



