314 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



pair of tumid lips between which is the narrow opening 

 of the neuropodial setal sac .which contains the crotchets. 

 The external opening of the sixth (last) nephridium is just 

 behind the dorsal end of the ninth neuropodium. x 6. 



Fig. 20. Ventral stem of gill of younger Laminarian 

 worm. This stem is about half the length of the corres- 

 ponding one shown in the preceding figure, and its lateral 

 branches are still comparatively simple. x 20. 



Fig. 21. Lateral branch, from one of the dorsal stems 

 of the gill shown in fig. 19, bearing twenty-two gill 

 filaments, x 20. 



Fig. 22. Fourth right gill of a littoral specimen 

 about 110 mm. long. The gill consisted of ten main 

 stems, eight of which have been cut away. The blood- 

 vessels are seen traversing the basal membrane. The 

 lateral twigs are fewer in number and not so richly 

 branched as in Laminarian specimens. x 20. 



Plate III. 



Fig. 23. Dissection of a large Laminarian specimen 

 (250 mm. long) cut oj)en along the mid-dorsal line to show 

 the anatomy. The alimentary canal is pushed over to the 

 left side, and most (three-fourths) of the tail has been cut out. 

 The proboscis is about half extruded. The dorsal portion of 

 each left gill is seen. The gastric plexus is shown full of 

 blood, and the heart about half expanded. The funnel 

 only of the first left nephridium is seen, the rest of the 

 organ being covered by the oesophagus. The funnel of 

 the third left nephridium is hidden by one of the 

 oesophageal glands. The funnel of the fifth right nephri- 

 dium has pushed its way through the interval between two 

 of the oblique muscles. The blood-vessels of the sixth 

 right nephridium have been pushed forward one annulus, 



