216 j. h. ashworth. 



External Characters of Heteroxenia Elizabeths. 

 (PI. XXII., Fig. 37). 



Bourne (1895) has already described the external characters 

 of a colony similar to this one, but a brief description will be 

 given here. The colony is somewhat triangular in shape, the 

 base of the triangle being formed by the polyp-bearing summit 

 of the stem. The stem is slightly flattened, and is narrow at 

 its lower end, gradually widening from below upwards. The total 

 length of the stem is about 30 mm., its breadth at the base 12 mm. by 

 6 - 5 mm., its breadth at the top 23 mm. by 6 mm. 



The non-retractile polyps (A) are long and slender, and measure on 

 an average about 15 mm. in length (including the tentacles), though 

 a few specimens reach almost 30 mm. in length. The polyps are 1 mm. 

 to 2 mm. broad. The tentacles of the polyps measure 4 mm. to 5 mm. 

 in length, and bear on the inner side two series of rather slender 

 pinnules, each series consisting of three rows of about sixteen to 

 twenty-four pinnules in each row. In one or two of the tentacles 

 examined, the pinnules at the base are so arranged that it is difficult to 

 say whether they are in three or four rows on each side of the middle 

 line. The pinnules in the middle of the tentacle measure about - 5 mm. 

 in length, and are about four times as long as they are broad. The 

 middle line of the tentacle is free from pinnules along the greater pai't 

 of its length. The polyps are 1 mm. to 3 mm. apart, but they are 

 closer together round the edge of the summit of the stem than on the 

 middle portion of the summit. Around the edge of the summit of the 

 stem there are many small polyps in all stages of development, — in 

 fact, all the polyps near the edge of the summit are small ones, the 

 large ones being situated in the middle portion of the polyp-bearing 

 area. 



The walls of the polyps are thin, and when the colony is removed 

 from spirit the polyps fall together and form a confused mass on the 

 end of the stem. 



Between the bases of the polyps there are many closely apposed 

 small zooids (Fig. 37, S.), quite different in appearance from buds or 

 young polyps. The siphonozooids, are from six to ten times as numer- 

 ous as the polyps or autozooids, and they occur all over the summit of 

 the stem. The siphonozooids are all similar in appearance, being 



