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-esophageal mass. After this follow the five thoracic 
gangha of the chelz and the legs, and, lastly, the s¢x abdo- 
minal gangha. 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 
Excretory. 
Fig. 147.—LaTERAL View or NepHrops. (Ad nat.) 
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 ccelomic body-cavity into which 
they can open. 
