136 



contraction of the dorso-ventral muscles will effect the 

 raising of the branchial roof, and thus produce a corres- 

 ponding increase in the capacity of the branchial 

 chamber. When the muscles relax, the weight of the 

 superimposed digestive gland and goiiad will be sufficient 

 to depress the roof and decrease the volume of the 

 branchial chamber. 



Although it is difficult to understand the precise 

 function of these muscles, it must be conceded that their 

 action may be of supreme importance in connection with 

 the branchial chamber, either as a current regulator or as 

 an accessory current-producing organ. It will not be 

 surprising if additional investigations on this point throw 

 new light on some of the problems discussed above. 



EXCEETOEY SYSTEM 



(PL X, figs. 57, 58, 59, Text figs. 11 and 12). 

 Excretion is performed in three different parts of the 

 body. 



(i) by the Anteiinary glands and their connections. 

 (ii) by the Ferment cells of the digestive gland. 

 (iii) by the Branchial excretory organ. 



(i) THE ANTENNARY GLANDS AND CONNECTIONS. 



These form a complicated system of organs at each 

 side of the body. The right and left sides, which are 

 similar to one another are absolutely separate, although 

 in certain places the two parts are in very close contact. 

 This excretory organ is a coelonioduct*, and may be 

 divided into three portions on each side. The first part, 

 or the antennary gland (" green gland," " rein anten- 

 narie "), is situated in the cephalic region immediately 

 behind the eye socket. It is a small spongy mass of a 

 * Goodrich. Various papers in Q.J.M.S., Vols. XXXVII-XLV. 



