350 Dr. H. M. Yernon. The Effect of Stateness of the 



" The Effect of Staleness of the Sexual Cells on the Development 

 of Echinoids." By H. M. Yernon,. M.A., M.D., Fellow of 

 Magdalen College, Oxford. Communicated by W. F. R 

 Weldon, F.B.S. Eeceived June 27, 1899. 



The effect of varying degrees of staleness of the ova and sperm of 

 an organism upon subsequent development appears to have been very 

 little studied, though such a condition must obviously be a factor of 

 frequent occurrence under natural conditions. Thus in most of the 

 Coelentera, Echinoderms, and in some of the worms, it would seem to 

 be a matter of chance whether the ova and spermatozoa come into 

 contact when freshly shed, or only many hours after extrusion. In 

 some mammals also, especially in man, the relative degree of freshness 

 of ovum and spermatozoon at the time of fertilisation is entirely a 

 matter of chance. 



The chief connection in which the question of staleness has been 

 hitherto studied is that of polyspermy. Thus O. and R. Hertwig 

 found* that on crossing certain species of Echinoderms, as the ova of 

 Sphcerechinus granulans wibh the sperm of Strongylocentrotus lividus, 

 more and more of the ova were fertilised up to a certain point if they 

 were kept for an increasing number of hours in sea water, but that 

 after this point they began to undergo polyspermy in an increasing 

 degree, and to develop abnormally, To what precise extent is this 

 tendency present, however, and how is it affected by the staleness of 

 the ova on the one hand, and of the sperm on the other ? Also, do 

 the normally developing ova of stale sexual products continue to 

 develop equally well with those from fresh products,- or not 1 Such 

 are the questions it is attempted to answer in this paper. 



The method of experiment was very simple. The ovaries and testes 

 of ripe specimens of the Echinoid Strongylocentrotus lividus were shaken 

 in jars of water, and portions of the contents of these were mixed, either 

 immediately, or after a given number of hours. The mixed solutions 

 were allowed to stand for an hour, and were then poured into beakers 

 and diluted with about ten times their volume of water. Twenty-four 

 hours later, some of the stirred up contents were introduced into a 

 small glass cell, and a drop of corrosive sublimate solution added to 

 kill the blastulaB and make them sink to the bottom. The numbers of 

 normally developing blastulse, and of abnormally developing and 

 unsegmented ova were then counted, 300 to 500 being usually 

 enumerated, in order to get an accurate estimate. In all cases the 

 mixed ova from two or more ripe specimens were used, and were 



* 4 Experimentelle Untersuclmngen uber die Bedingungen der Bastardbefruch- 

 tuug.' Jena, 1885. 



