No. 2.] MORPHOLOGY OF THE ACT/JVOZOA. 135 



the genus it secretes a case, open at both ends, and composed of 

 hardened mucus and nematocysts. Animals removed from the 

 case and kept in an aquarium rapidly secrete for themselves a 

 new habitation, which, however, is naturally thinner than the 

 original one and of a lighter color, being almost white, while 

 normally the tube is dark gray, due to staining by the black 

 mud with which it is in contact. The inner surface is purplish 

 gray, being tinged by the pigment of the animal. 



The largest specimen I obtained measured about 20 cm. in 

 length, with a diameter at the middle of 1.5-2 cm., and at the 

 disc of 1.8-2.5 cm. The outer tentacles measured 3.4 cm., while 

 the oral series measured 1-1.2 cm. These measurements fall 

 very short of those given by Verrill, who states that the largest 

 specimens in expansion measure 60-70 cm. in length, with a 

 diameter at the disc of nearly 4 cm. and at the middle of the 

 column of 2.5 cm. My preserved specimens measure 5.5-6 cm. 

 in length, and about 1.5 cm. in diameter. 



The color of the column is some shade of brown (PI. VI., 

 Figs. I and 2), varying from pale chocolate-brown to deep pur- 

 plish brown. The upper part is always darker than the lower, 

 and in some cases the column is marked with longitudinal lines 

 of a lighter shade than the ground color. The marginal ten- 

 tacles are of a paler brown than the column, except the outer- 

 most, which are purplish blue. The oral tentacles in all the 

 specimens I observed were pure white; Verrill, on the other 

 hand, describes them as being darker than the marginal ones, 

 and marked with white longitudinal lines. In the Beaufort 

 specimens, however, the tentacles of both series are unmarked 

 by lines, spots, or annulations. The disc is yellow with white 

 lines crossing it radially. 



The column is cylindrical and smooth, tapering gradually 

 towards the posterior extremity, which is rounded, and bears a 

 small terminal pore. The marginal tentacles vary somewhat in 

 number. Verrill states that they are 125 or more, but in the Beau- 

 fort specimens they did not amount to 100, varying, according to 

 the counts made, from 89 to 94 (95 i"). We know from the obser- 

 vations of Vogt and Fischer that there is always an odd number, 

 the unpaired tentacle corresponding to the space bounded by 

 the ventral directives. The absolute number of the tentacles 

 perhaps increases throughout the entire life of the animal, and 



