29 



The fifth experiment was made on the 1 3th of December. Six ova 

 were exposed for an hour and twenty-five minutes to a temperature 

 falling from 82, which it was at the beginning, to 78, which it was 

 at the end. Two became opaque ; in these no marks of progress 

 could be seen of development, thus indicating that they were dead at 

 the time of trial. Four remained transparent ; in these, under the 

 microscope, embryo-fish were seen with an active circulation of the 

 blood-corpuscles. One of them was hatched on the 31st of Decem- 

 ber ; one, the last, on the 6th of January. 



The sixth experiment was made on the 20th of December, on six 

 ova, containing living embryos. They were exposed for an hour and 

 twenty-eight minutes to a temperature of about 98, and this during 

 the whole time. When taken out, they had not lost their trans- 

 parency, but in each the heart's action was arrested, and death was 

 the result : they all sooner or later became opaque, from the common 

 cause, the imbibition of water. 



The seventh experiment was made on the 21st of December, on six 

 ova, in which the circulation was distinct in the foetal fish. After 

 an exposure for an hour and five minutes to a temperature of 70 

 rising to 82, in five, on cooling, the circulation was found active ; 

 in one, stopped, which was dead ; two were hatched on the 5th of 

 January ; three, the remainder, on the 7th of the same month. 



The eighth experiment was made on the 23rd of December, on six 

 ova, each containing a living foetus. They were exposed to a tem- 

 perature falling from 84 to 82 during an hour and twenty minutes. 

 Examined after the water had cooled, in one, the circulation was seen 

 pretty distinct ; in two, very feeble ; in three, the blood-corpuscles 

 appeared to be stagnant. Examined on the following day, the cir- 

 culation was seen active in all. One was hatched on the 5th of 

 January, the other five in the two following days. 



The ninth experiment was made on the 24th of December. Six ova 

 were exposed for two hours and four minutes to a temperature falling 

 from 72 to 70. Examined a quarter of an hour after, and before 

 the water was cold, the circulation was found vigorous in all. One 

 was hatched on the 2nd of January, the remainder between the 5th 

 and 8th. 



The tenth experiment, and the last of its kind that I have to 

 describe, was made on the 2nd of January. Six ova, in each of which 



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