PRRTTIJSATION OF THE EGGS OF ANIMALS. IGl 



were about 10 mm. diameter and 1 — 2 mm. high. The 

 upper and under surfaces (in which the dii-ection of rotation 

 appears reversed) are best examined with a magnification of 

 from 70 — 240 diameters. In the case of Echinus the rota- 

 tion is well seen under these conditions for ten minutes after 

 the beginning of the experiment, fairly well for fifteen 

 minutes, and ceases to be seen in about twenty minutes, when 

 the spermatozoa have nearly all come to rest. 



The rule given above as regards rotation upon surfaces 

 was found to hold good not only for the Echinoidea, but 

 for every group of the Echinodermata. Open drops were 

 employed in the test. The names of the species examined 

 have already been given. 



It has already been mentioned that Dewitz^ discovered that 

 the spermatozoa of certain insects revolve upon surfaces. 

 This has been confirmed by Ballowitz.2 Dewitz also found 

 that the direction of revolution Avas counter-clockwise. It 

 is a remarkable fact that the spermatozoa of groups so far 

 apart as the Insecta and Echinodermata should thus be 

 affected by surfaces in the same manner. It is not improb- 

 able that a similar phenomenon will be found for the 

 spermatozoa of yet other animals. 



Immediately after my work had been brought to a close a 

 preliminary paper was published by Dnngern,'^ entitled "Die 

 Ursachen der Specietiit bei der Befruchtung." In it the 

 author communicated his discovery of the counter-clockwise 

 rotation upon surfaces by the spermatozoa of Spha3rechin us 

 and Arbacia. He failed, however, to observe any rotation 

 of the spermatozoa of Echinus, but this, he states, took 

 place after the addition of certain (unnamed) '■ stimulatino* 

 substances," Since it was in ordinary sea-water and with 

 the spermatozoa of Echinus that I (independently) first 

 became aware of the rotation, and since with this species 



1 Dewitz, loc. cit. 



^ Ballowitz, " Untersuchungen iiber die Strnctiir der Spermatozoon, etc.," 

 Zeitsclir. f. Zoologie,' Kd. 1, 1890, pp. 392, 393. 

 ^ Dungern, 'Centralbl. fur Pliysiologip,' April, 1901, Heft 1. 

 VOL. 46, PART 1, NEW SERIES. L 



