SECT. II] FAT METABOLISM ii8i 



yolked undeveloped eggs fill up the uterine cavity; their second set 

 shows what has happened by the time the embryos have reached the 

 length of about 4 cm., a dry weight of 4-45 per cent, and a nitrogen 

 content of 1-95 per cent. Finally, their third set of data concerns 

 the fish after the embryos have left the uterus. The first point of 



Table 172. 

 Reach & Vidakovich's figures (in grams) : 



Liver Ovaries _ 



Note. In the "Spring-torpedo" the eggs have just come into the uterus; the analyses were made in June, 

 fertilisation probably having taken place in April. In the "Summer-torpedo" embryonic growth has proceeded 

 considerably, the analyses being made in July. The "Autumn-torpedo" has just given birth to the 6-10 embryos 

 and its ovary contains yolked eggs from 10-20 mm. diameter; the analyses were made in August. 



interest to be drawn from the table is that the fatty acids decrease 

 notably from 66 1 to 499 mgm. per egg — a loss of 24-5 per cent. There 

 is no means of telling, of course, whether this loss is all due to com- 

 bustion, but, even if it were, the amount must be much less than the 

 corresponding loss in a terrestrial egg such as that of the chick, for 

 the latter has 30 per cent, of its yolk as fat and the former only 

 9'4 per cent. It may therefore be supposed that the main source of 

 energy in the selachian egg is protein. As the table shows, the per- 

 centage of fatty acids in the whole egg diminishes from 9-4 to 7-2. As 

 regards the maternal liver and ovaries. Reach & Vidakovich did not 

 confirm Polimanti and Lo Bianco, for the livers of their fishes hardly 

 changed at all in per cent, of the total body-weight, and what change 

 there was during "pregnancy" was in the reverse direction. Nor did 

 the percentage of fatty acids in the liver show any of the changes 

 suggested by Polimanti. Reach & Vidakovich's iodine number results 

 were interesting. 



