-552 



Dr. K M. Vernon. The Effect of Stateness of the 



average, 0*5 per cent, per hour for each of the first six hours. This value 

 is put, for convenience, against the " after six hours " line in the table,, 

 though it should rightly be placed between the " directly " and " after 

 six hours " lines. The other values are arranged in the same way. We 

 see then, that of the ova developed in tank water, from 0*5 to 1*8 per 

 cent, per hour underwent abnormal development up to the 27th hour, but 

 that then the percentage rapidly increased, till from the 33rd to the 

 35Jth hours, it reached to 13*5 per cent. In the case of the ova kept 

 in pure sea water, the result was still more striking. Thus till the 

 24th hour only 1*5 per cent, or less per hour developed abnormally,, 

 but from the 27th to 30|th hour, no less than 18*9 per cent. 



Time of 

 fertilisation. 



Per cent, diminution per hour. 



Tank water \ Tank water 

 (1,000,000 per litre). (49,000 per litre). 



Pure water 

 ,000 per litre) . 





(71 -6) 

 0-7 



(83 -9) 



(86-0) 



After 9 hours 



0-7 



0-2 



„ 20 „ 



3-3 



6-6 



3 



„ 24 „ 



5 9 



1-1 



13 '8 



29 „ 



0-5 



0-05 



3 5 



» 32i „ 



0-2 



o-o 



1-5 



„ 46 „ 



0-06 





0-2 



In this next table a similar series of observations is recorded, but in 

 addition a third series of determinations was made, in which ova and 

 sperm were kept in about twenty times as great a volume of water as 

 was used in the other experiments. Thus it was thought that perhaps 

 the keeping together of very large numbers of ova and of spermatozoa 

 in small volumes of water might tend to increase the rapidity of their 

 deterioration. As far as this single result can show, however, just the 

 reverse is the case. Thus when only 49,000 ova per litre were kept 

 together, the maximum rate of deterioration was reached between the 

 9th and 20th hours, whilst when 1,000,000 per litre (about the usual 

 state of dilution) were kept, the maximum rate was not reached till 

 the 20th to 24th hours. 



In pure sea water, with a dilution of 680,000 ova per litre, the 

 maximum rate was also between the 20th and 24th hours, but a fair' 

 number also degenerated between the 24th and 29th hours. In this 

 table it will be noticed that the actual percentages of blastulse have 

 been omitted, and only the percentage numbers of ova per hour under- 

 going abnormal development given. The numbers given in brackets 

 against the " fertilised directly " line indicate the percentages of normal 

 blastulse produced on immediate fertilisation. 



