32 



of air. Owing to a mistake, they were not forwarded. Examined 

 on the following day, five ova were found hatched, the young fish 

 dead ; in the one ovum remaining unhatched, the foetus was alive, 

 the circulation active ; on the 9th it burst its shell ; the young fish 

 was vigorous. 



As I could not with any certainty determine, at the time the ex- 

 periments were commenced, what eggs were impregnated and alive, 

 and what were not, I had at the beginning thirty ova taken indis- 

 criminately from the common stock, and put apart in a glass vessel, 

 the water in which was also changed daily. Of this number, seven 

 were found in progress of development on the 14th of December, or 

 23 per cent.; the rest had become opaque. One of the seven was 

 hatched on the 31st of December, the others in succession, the last 

 on the 8th of January. 



Further to arrive at a proximate average of the proportion of im- 

 pregnated and unimpregnated ova, or living and dead, on the 14th 

 of December, when in the living ova the circulation was distinct 

 under the microscope, and the embryos were visible even to the 

 unaided eye, I examined the whole number then remaining, viz. 405, 

 thus reduced, owing to 67 having been removed, one after another 

 having become opaque, and 152 having been taken out for the pur- 

 pose of experiments. Of these 405 remaining, 138 were found alive, 

 each containing a well-formed embryo, and 267, though still trans- 

 parent, without life, no marks of organization being to be seen in 

 them, either with the naked eye or under the microscope. Hence, 

 irrespective of the 152 experimented on, the proportion of living to 

 dead on the 14th of December would appear to be as 138 to 364, 

 or about 25 per cent. And, with the exception of two which died 

 after the 14th, all those then alive were hatched, the first on the 

 31st of the same month, the last on the 9th of January. 



What are the conclusions to be drawn from these results ? From 

 those of the first series of experiments, may it not be considered as 

 proved that the power of resisting an undue increase of temperature 

 is possessed in a higher degree by the ova in an advanced than in an 

 early stage of development, the degree probably being in the ratio 

 of the age ? From those of the second series, is it not as manifest 

 that the power of bearing distant transport, and of retaining life in 

 moist air, is in like degree increasing with age ? And from both, 



