162 A. H. REGINALD r.ITLLER. 



I have made scores of observations upon the phenomenon in 

 question, I am at a loss to explain his negative results. The 

 detailed paper which he has promised will doubtless clear the 

 matter up. At present, however, I am unable to accept his 

 account of the " stimulating substances." 



From the published figures and from my own observations 

 the spermatozoa of the Echinoidea appear to be radial struc- 

 tures. The fact, however, that they rotate as a rule only in 

 one direction shows that they cannot really be thus con- 

 structed. The researches of Ballowitz^ upon bird and insect 

 spermatozoa have demonstrated the complexity of their form, 

 which is often in part spiral. Perhaps a minute investigation 

 would also lead to similar results in the case of the Echinoidea. 

 Careful observation of the rotating spermatozoa reveals the 

 fact that a few spermatozoa, probably not more than 1 percent., 

 revolve in a direction contrary to that of the great majority. 

 All that can be seen of a spermatozoon during its rotation 

 upon the under side of a cover-glass is its head. This moves 

 rapidly round in a circle. The tail is quite invisible. The 

 centre of the circle remains fairly constant in position. 

 Sometimes, however, the spermatozoon makes a wider curve 

 for a while, and then begins to make circles with the same 

 diameter as before around a new centi-e. The width of the 

 circles varies. It appears, however, in the case of Echinus 

 to be slightly less than 0"05 mm., the length of a sperma- 

 tozoon. The rate of rotation of the actively moving 

 spermatozoa in any preparation is fairly constant, as may 

 easily be observed by direct comparison of rotating indi- 

 viduals. In the case of Spha^rechinus a normally rotating 

 spermatozoon was observed to make 100 circles around one 

 point in 90 seconds, which gives a i-ate of slightly more 

 than one revolution a second. The diameter of the circle is 

 about the same as in the case of Echinus. Assuming it to be 

 00 !• mm., the rate of movement of the head is calculated to 

 be approximately 0*12 mm. per second, or 7 mm. per minute. 

 If a supported cover-glass preparation containing a drop 

 1 Ikllowitz, loc. cit., p. 317- 



