NEPHROPS. 219 



of the mouth. The ganglia corresponding to them follow 

 suit and fuse with the primary brain to form one mass. 



In a similar manner the ganglia of the next six append- 

 ages, which are all jaws or foot-jaws, fuse to form one large 

 sub -oesophageal mass. After this follow the five thoracic 

 ganglia of the chelae and the legs, and, lastly, the six abdo- 

 minal ganglia. The last supplies both the sixth segment 

 and the telson, and thus may be two (6th and 7th) fused 

 ganglia. 



In this way the primitive chain of twenty ventral ganglia 

 is reduced in number by fusions at each end till twelve only 

 remain. 



The lobster excretes nitrogenous waste products by a pair 



of green glands in the head, which may be a pair of much 



modified nephridia. Each consists of a complex 



excretory tube leading to a bladder, which opens 



to the exterior by the excretory pore on the ventral side of 



Fig. 147. — Lateral View of Nephrops. {Adnat.) 



Scaphognathite. Pleurobranch. 



3rd 

 Maxillipede. 



Chela. 



With branchial plate removed. Behind the scaphognathite are the epipodites 

 of the first two foot -jaws, then follow the five podobranchs and their epipodites. 

 The arthrobranchs and three of the pleurobranchs are hidden. 



the antenna. The excretory products are thus discharged 

 into the stream of water emerging from the branchial chamber 

 (see below). We may notice that the tubes have no internal 

 nephrostome, for there is no coelomic body-cavity into which 

 they can open. 



