6 McMURRICH 



The two white specimens are of about the same size and 

 measure 8 cm. in height and about 4 cm. in diameter. 



As stated above, considerable variation occurs in the length 

 of the tentacles. Thus in a brown individual measuring 4 cm. 

 in height the inner tentacles measured 3.5 mm. in length, while 

 in another individual of the same variety, measuring only 1.3 

 cm. in height, the inner tentacles were 5 mm. long. In the 

 large orange specimen the inner tentacles measured about 4 mm. 



Structure. — Considerable differences in the structural details 

 are found in the various individuals, but these seem to be corre- 

 lated, in part at least, with differences of age, that is to say of size. 

 A comparison of the structure of the smallest individual with that 

 of the largest would almost lead one to regard the two as dis- 

 tinct species ; intermediate conditions, however, occur and it 

 seems clear that the differences are growth differences associated 

 with some tendency to variability. 



The mesoglcea of the column wall has a fibrillar structure, 

 or is even distinctly fibrous, especially in the region of the 

 sphincter. Above the level of the collar the wall is much 

 thinner than below, the difference being due to a difference in 

 the thickness of the mesogloea. The circular musculature of 

 the column is well developed and in the smaller specimens, its 

 mesoglceal processes are clearly marked off and show a tendency 

 to branch slightly. In the larger forms, however, they are 

 sometimes stout, with rounded extremities and may contain 

 muscle cavities imbedded in their substance. 



The sphincter is always well developed and is imbedded in 

 the mesogloea in the collar region. In different individuals, 

 however, it presents decided differences in its minuter structure 

 and I give on PL I three figures (Figs, i, 2 and 3) showing 

 some of the variations observed in the present collection. In 

 Fig. I, which is from an individual measuring 1.5 cm. in height, 

 the muscle cavities are more or less circular and are scattered 

 irregularly in the mesogloea, being separated by a narrow band 

 from its endodermal surface. In Fig. 2, which represents only a 

 portion of the sphincter of an individual of the white variety 

 measuring 8 cm. in height, the muscle cavities are much more 



