32 



THE PHYSIOLOGY OF EARTHWORMS 



as a starting point van Gansen (1959a) argues that the two regions 

 of the gland both secrete calcium carbonate, but in different ways. 



Fig. 10. Anatomy of calciferous glands of Eisenia foetida. To the 

 right a vertical section passing outside the chambers of the gland 

 to show the blood sinus system. In segment 12 a transverse section 

 of the chambers to show distribution. To the left a vertical section 

 passing through a chamber. Sinuses marked in black, calciferous 

 zones with small circles, and mucus areas with horizontal 

 hatching. 11, 12, 13, 14 indicate numbers of segments (from van 

 Gansen, 1959a). 



The posterior region receives its blood supply direct from the 

 intestine and the fluid contents of the gland cells are almost 

 identical with the blood. By a process of filtration, which pre- 



