430 



Mr. G. Smith. 



seen. In addition to the greatly increased glycogen deposits in the liver, 

 cells containing large masses of glycogen are abundant in the subdermal 

 connective tissue and in the tissue between the liver cells. 



If the liver of a crab in this condition is extracted for glycogen with hot 

 potash solution, and the amount estimated as sugar by titration, the percen- 

 tage of glycogen will be found to be very high, far higher than at any other 

 time in the crab's life-history. 



If now we take sections through the liver of a crab that has recently 



mm 



; : , ■'^'^ rX 



Fig. 9. 



Fig. 10. 



Fig. 



9. — Section through portion of liver, tube of Carcinus just about to moult. The 

 storage cells are crammed with small round glycogen granules. 

 Fig. 10. — Section through portion of liver tube of ditto, some days after the moult. 



Reserve material is almost entirely absent from storage cells, which are full of 

 protoplasm. 



completed its moult and has the shell soft and flexible, we shall find it in the 

 condition shown in fig. 10. The storage cells are now almost depleted of 

 glycogen, and consist of protoplasm in which a few globules of fat, especially 

 at the basal ends, are beginning to appear. The subdermal glycogen will also 

 be found to have very much diminished in quantity. It is clear that the 

 glycogen deposited in the liver and subdermal tissues just before the moult 

 has been used up in the formation of the new skin and tissues during the 

 rapid process of growth which follows the moult. 



If, finally, we take sections through the liver of a hard-shelled crab at a 

 period intermediate between two moults, when growth is not proceeding, we 



