148 



Development of the Antennary Gland. 

 According to Waite,* who studied the development of 

 the gland in Homarus, the end sac alone arises from the 

 mesoderm when the embryo is only five days old, and its 

 lumen is for a long time completely enclosed by meso- 

 dermal cells. An ectodermal ingrowth (which ultimately 

 becomes the renal tube of the labyrinth) occurs at about 

 the twenty-eighth day. The lumen of the end sac does 

 not become continuous with that of the labyrinth until the 

 embryo is nearly 300 days old. The complications in the 

 walls of the renal tube to form the labyrinth do not occur 

 until the third larval stage. The bladder is formed by a 

 dorsal outgrowth of the ectodermal tube. Therefore, only 

 the cavity of the end sac represents part of the original 

 coelom. The renal tube of the labyrinth, the bladder and 

 the ureter are all ectodermal in origin. Although the 

 development of the green gland in the Brachyura has 

 not been investigated, there is no reason to believe that 

 it presents any striking differences from that of the 

 Ma crura. 



(ii) Ferment Cells of the Digestive Gland. 



Part of the contents of the ferment cells are of an 

 excretory nature, and when the contents of these cells 

 pass down the digestive tubules into the mid-gut the 

 excretory products are separated away and are carried 

 to the exterior along with the faeces. The ferment cells 

 of the digestive gland lake up methylene blue when this 

 colouring matter is injected into the body of the living 

 animal. The large coloured mass inside each ferment 

 cell is coloured light blue. Inside this mass there are 

 small bodies, which take a dark blue stain. According 

 to Cuenot, in five days after the experiment the blue 



* Waite. Bull. Mm. Harv., Vol. XXXV, No. 7 (1899). 



