SPERM ATOGENESIS INSEMINATION 173 



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. Buller concludes, therefore, that the nature of the surface 

 is not an important factor in the process. 



Ballowitz expresses the opinion that the circles described by 

 insects' sperms are simply the modified spirals made by the free- 

 swimming cells. Buller thinks that this view, which provides a 

 purely mechanical explanation, is also probably correct for the 

 spermatozoa of Echinoderms. 



Since counter-clockwise rotation upon surfaces has been observed 

 in the spermatozoa of two groups as widely separate as the Insecta 

 and the Echinodermata, it would seem probable, as Buller remarks, 

 that it will be found to occur in other animals. 



The spermatozoa of Mammals, in traversing the female passages 

 after copulation, make their way upward towards the ovaries in 

 opposition to downward currents set up by the cilia of the lining 

 epithelia. Kraft * has show r n that when rabbits' spermatozoa, in a 

 state of feeble motion, are placed upon the inner wall of the oviduct 

 their movements become more vigorous and they swim against the 

 current which the cilia produce. Roth 2 also has succeeded in 

 experimentally illustrating the same fact. 



It is commonly stated that in man the passage of the spermatozoa 

 from the vagina inwards is assisted by a contraction of the muscular 

 wall of the uterus, which compresses the cavity of that organ into 

 which the sperms are drawn when relaxation takes place. 3 The 

 contraction of the uterus is said to be a reflex action resulting from 

 copulation. It has also been suggested that, during copulation, a 

 mucous plug which is ordinarily contained in the cervix may be 

 temporarily and partially expelled into the vagina and afterwards 

 withdrawn with the spermatozoa adhering to it. 4 



So also Heape "' has shown that in the rabbit the passage of the 

 spermatozoa into the uterus is probably assisted by a sucking action 

 on the part of the latter organ. The os uteri, which is situated 

 above the ventral wall of the vagina, was observed to dip down 

 into the seminal fluid at the bottom of the vagina, and then to be 

 withdrawn again in conjunction with a peristaltic contraction of the 



1 Kraft, " Zur Physiologie des Flimmerepithels bei Wirbelthieren," Pjliige^x 

 A /</'<; vol. xlvii., 1890. 



2 Roth, " Ueber das Verhalten Ijeweglicher Mikroorganisinen in stromender 

 Fliissigkeit," D<'>it.-l,<- ,&!. ]Y<ii-l,,',,Krl,,-ift, vol. xix., 1893. Verworn (loc. cit.) 

 describes this property of spermatozoa under the name of rheotaxis, which, he 

 says, is a special kind of barotaxis. See also Adolphi, " Die Spermatozoen der 

 Saugethiere schwimmen gegen den Strom," Ann/. An:., vol. xxvi., 1905. 



3 See Beck, "How do the Spermatozoa enter the Uterus > " Amer. Jour, of 

 Ol>*tet., vol. viii., 1ST"). 



4 See Williams, Obstetrics, New York, 1004. 



"' Heape, "The Artificial Insemination of Mares," Vet?r!nr!<m< 1898. 



