520 



THE FUK SEALS OF THE PRIBILOF ISLANDS. 



<n;.-' 



to 2 cm. to Ih cm. Uuyieldiag to the touch, dirty greenish-brown in color. Portions 

 of the surface of the colonies smooth, almost shiny, but for the most part a surface 

 crust of test becomes broken up and the broken fragments partially or wholly peeled 

 off. Where these ineces are fully removed sand adheres to the underlying ex]iosed 

 test. By i-eason of the conditions of the surface test thus described the colonies 

 usually piesent a ragged appearance, hence the specific name chosen. (Fig. 17 A y.) 

 Test. — Matrix firm, relatively large iu quantity, there being a large central core 

 in each colony, into which the zooids do not reach, and the zooids themselves are 

 rather remote, making the intervening test considerable in quantity. Cells numerous, 

 of many sizes, some of them large. The cells contain a diffuse greenish coloring 

 matter, to which is due the tint of the test when seen in section. The central core of 



test penetrated by a wide areolar mesh work of rather fine 

 fibers. (Fig. 17 A.) 



Zooids. — Moderately numerous, not visible on surface 

 view of the colony. Owing to their variously twisted con- 

 dition and the diflering angles which tliey form with the 

 M.cx surface of the colony, the entire length of a single zooid 

 is seldom seen uncut on radial sections of the whole colony. 

 Average length of individuals, about G mm., about one-half 

 /^ of which is postabdomen. Thorax about 2 mm.; abdomen 

 about 1 mm. Postabdomen joined to the i)ostero-ventral 

 side of the abdomen, somewhat to the left side, by a nar- 

 row peduncle. (Fig. 18.) 



Mantle. — Feebly developed. Longitudinal muscle fibers 

 in distinct bands; circular fibers almost wholly absent, ex- 

 cept in the siphons, and here tliey are not strongly developed. 

 Branchial apparatus. — Orifices very indistinctly seen on 

 the surface of the colony. On removal from test, branchial 

 siphon found to be encircled by six unequal rather pointed 

 lobes. Atrial languet not easily seen intact, of moderate 

 length, broad at base, ta])ering rapidly to a blunt point, 

 which, however, sometimes shows traces of two or three 

 lobes. 



Branchial sac removed whole from test with much diffi- 

 culty, this due to the delicacy of it and tlic mantle, and the 

 fact of its being thrust up more or loss sidewise into the 

 S[)ecially dense, firm, and rather thick layer of surface test. This displacement 

 apparently caused by the numerous large embryos contained in the atrial chamber. 



Organs of the peripharyngeal region distinguished with much difficulty; ganglion 

 moderately large, tentacles about 25 in number, of different sizes, the largest ones 

 but few, not large. All situated close around the base of the siphon. Branchial sac 

 containing about 12 series (in some specimens 13, and some apparently 10 or 11) of 

 stigmata. Cilia of tlie stigmata unusually long and stout. In some specimens 

 the stigmata quite pointed and with a peculiar process, sometimes of considerable 

 length at the ends. A well-developed muscle band in each interserial space. Dorsal 

 languets long, sometimes reaching more than halfway across the sac, about e(]ual in 

 number to the series of stigmata. (Fig. 18, Slg.) 



