TUBE OF PANTHALIS. 335 



line to the posterior extremity. After death the course 

 of this vessel is marked by a longitudinal ventral ridge 

 which has been referred to by a previous writer as the 

 covering of the nerve cord. The ventral surface of the 

 animal was opalescent, with a golden shade towards the 

 sides, caused probably by the spinning glands and setae of 

 the parapodia. The posterior extremity of the body was 

 broadly forked, owing to the last pairs of parapodia being 

 usually directed backwards. 



As specimens in alcohol are in every way much con- 

 tracted and altered, this description of the large Panthalis 

 under observation will probably be of interest, the dimen- 

 tions given being a rough guide to the relative positions 

 of the organs, though other specimens which I have 

 examined vary very considerably both in size and colour. 



The third day after being deposited in the tank, the 

 animal was evidently quite settled, and it proceeded to 

 complete the burrow against the glass, with the object of 

 making an o^Dening at the left hand extremity of the old 

 tube. Early in the morning of that day I found Panthalis 

 had forced about f of an inch of its body through the mud 

 at this point, and was "prospecting;" on my approach 

 this was quickly withdrawn ; but the animal remained in 

 the burrow the greater part of the day, thus affording 

 ample opportunity for observation of which I availed 

 myself by making careful sketches both with and without 

 the microscope. The most noteworthy occurrence of the 

 day was an example given by the animal of its power to 

 very largely expand the forepart of its body, which it 

 utilised for enlarging the diameter of its burrow. By 

 this means it lifted the old heavy tube fully 5- of an inch, 

 and almost rolled it way from the glass. By night, a 

 clear passage and opening into the water had been made. 

 The following morning I again found Panthalis, lying 



