GAMMARUS. 359 



from it to the exterior (PL II., con. t.), the whole being 

 surrounded by spongy tissue full of blood, and innervated 

 by brandies from the antennary nerve. The end-sac 

 occupies the lower part of the proximal end of the basal 

 joint; it is somewhat reniform, and the anterior end is 

 slightly narrower than the posterior one. It has very 

 thin walls, a delicate membrane supporting the epithe- 

 lium, each cell -of which contains coarsely granular proto- 

 plasm, and projects into the lumen or sac, its outer wall 

 being very convex. From the posterior end of the sac 

 arises the convoluted tube, which passes backwards and 

 downwards, then forwards and upwards, and then again 

 backwards and downwards into the antennary cone (PI. 

 II., ant. c), at the apex of which it opens to the exterior. 

 The tube is lined with cells containing fibrous protoplasm 

 and oval nuclei. It has a cuticula which becomes dis- 

 tinctly chitinous in the terminal section, and passes 

 directly into the cuticle covering the outside of the body. 

 Just before entering the antennary cone, the tube widens 

 considerably, forming a small bladder. 



A mass of spongy tissue occupies part of the protopo- 

 dite of the second maxilla, a convoluted tube running 

 through it to the exterior. It may be homologous with 

 the shell-gland of the Entomostraca according to Waite 

 (24), though Leydig considers that this gland is entirely 

 wanting in all adult Malacostraca. 



The groups of unicellular glands (PI. II., gl.), lying 

 just below the cuticle at the base of the thoracic and first 

 three abdominal appendages, and on the posterior margin 

 of the last three abdominal segments, are placed above the 

 point of exit of the efferent vessel of each appendage (PI. 

 III., fig. 1., gl.), and are evidently excretory in function. 

 In animals living under normal conditions they contain 

 brightly-coloured globules, usually orange or vermilion; 



BB 



