1048 CARBOHYDRATE METABOLISM [pt. in 



the life of^Ascaris is essentially anaerobic, the lost glycogen not trans- 

 formed into chitin cannot have been burnt. Weinland showed that 

 in Ascaris glycogen can be transformed into lower fatty acids such as 

 butyric and valerianic." Unfortunately, this is now quite discredited 

 (Slater). After fertilisation, the disappearance of glycogen continues 

 slowly, the percentage dropping from between 4 and 5 to rather less 

 than 2, and during segmentation this again falls to about i. It will 

 be remembered that in Section i-i2 (p. 328) reference was made to 

 Faure-Fremiet's demonstration of the origin of the chitinous mem- 

 brane of these eggs from their glycogen. 



His work was repeated and for the most part confirmed by 

 Szwejkovska. She found 4-85 gm. per cent, (of egg-contents) in 

 the Ggg at fertilisation, 2-01 after the eUmination of the first polar 

 body, and 0-756 after the elimination of the second. Of the 52 per 

 cent, of the glycogen disappearing between the first two points, she 

 found 47 per cent, as glucosamine in the chitinous envelope. Thus 

 the chitin in grams per cent, rose — 1*665 per cent, at stage i, 3-39 

 per cent, at stage 2, and 3-507 per cent, at stage 3. There was no 

 transformation of carbohydrate into fat, for the fatty acids also 

 diminished in amount during the interval between fertihsation and 

 the first cleavage: 



Grams % 



Volatile Non-volatile Total 

 After fertilisation ... ... ... 0-455 0-526 0-981 



After elimination of second polar body ... 0-343 0-361 0-704 



There was no change in the nitrogen-content. 



The silkworm Q.gg has also been the subject of researches on carbo- 

 hydrate metaboHsm. The first estimations were those of Vaney & 

 Conte, who noted a steady and gradual diminution of glycogen 

 throughout embryonic Hfe, from 3-08 per cent, dry weight at the 

 time of laying to 0-413 per cent, at the time of hatching. Their 

 figures are shown in Fig. 290 beside the data of Pigorini and of 

 Tichomirov, which correspond very well. There can be little doubt 

 but that the glycogen-content of the whole silkworm ^gg falls markedly 

 during the post-hibernation period, and it is probable that it rises 

 slightly during hibernation, although it may then remain constant. 

 Before hibernation the glycogen seems to fall a great deal also. 

 Tichomirov pointed out that the formation of chitin in this insect 

 (o-o to 0-21 per cent.) would probably account for some of the 



