144 MARINE BIOLOGICAL LABORATORY. 



appendages following the palps is situated more ven- 

 trally than either of the other two, and hangs down 

 from the ventral side of the animal. These are the 

 ovigerous legs. These anterior three pairs of appen- 

 dages are followed by four pairs of walking-legs. The 

 first pair of walking-legs is attached to what we may 

 call the first body segment. To the same segment 

 are attached the proboscis in the anterior middle line, 

 the pair of mandibles, the palps, and the ovigerous legs. 

 In the middle of the dorsal surface of the same segment 

 lie the four small simple eyes. 



The second pair of walking-legs (the fifth pair of 

 appendages) is attached to the second body segment, 

 the third pair of walking-legs to the third body seg- 

 ment, and the fourth pair to the fourth body segment. 



The body of the animal ends posteriorly in a small 

 process pointing upwards and backwards, which carries 

 the anal opening at its distal end, and is known as 

 the abdomen or rudimentary abdomen. 



Turning now to the internal structure, we find a 

 brain — dorsal to the oesophagus — followed by a ven- 

 tral chain of five pairs of ganglia for the middle region 

 of the body and a pair of small ganglia, continuous with 

 those of the trunk, within the abdomen. The first pair 

 of appendages is innervated from the brain ; the palps 

 and ovigerous legs from the first pair of ventral ganglia. 

 This first pair of ganglia is in reality the partially 

 fused first and second pairs. Each of the four pairs 

 of walking-legs has a pair of ganglia in its segment, 

 which supplies it with nerves ; and there is, as I have 

 said, a pair of ganglia in the abdomen. The diges- 

 tive tract runs as a simple straight tube through the 



