A TAXONOMIC STUDY ON PYROSOMA METCALF AND HOPKINS. 253 



transparent, and are not deeply colored. The test processes then 

 show the characteristic oblique truncation at their ends. These soon 

 lose their typical form, becoming long and irregular in shape, or 

 reduced in size and nodular. Among our largest specimens we find 

 exhibited all those color phases described by Savigny (1816, b) for 

 P. giganteum, as then named. Some are strongly bluish, but not 

 diaphanous as Savigny has described his. (This opacity may result 

 only from preservation.) Some are greenish; the majority, however, 

 are brownish or tan-yellow. But we fail to find the same corre- 

 lation between the color of the colony and the shape of the test 

 processes, which Savigny reports. The test processes for the most 

 part, even in specimens differing greatly in color, are thick, rounded 

 papillae,while, scattered here and there, are long, fingerlike tentacles. 

 An occasional specimen is completely covered with these longer 

 processes, which are sharply pointed and flattened at their tips as a 

 result of the extremely oblique truncation. The surface of the 

 colony usually presents a finely denticulate or wrinkled appearance 

 under magnification. The test wall, as seen in preserved specimens, 

 is rigid and cartilaginous. Its average thickness is about 7.5 mm. 

 (from 6 to 8 mm.), varying of course with different colonies. A 

 diaphragm is always present, although sometimes reduced. It is 

 relatively narrow in large colonies, where its width equals one-third to 

 one-half the radius of a section through this end of the colony. 

 Hence the aperture is relatively large. 



The dimensions of certain of our specimens are as follows : first, length 

 19.5 cm., width at open end 3.6 cm., at middle 3.9 cm., at closed end 2.5 

 cm.; second, length 31 cm., width at open end 4 cm., at middle 4 cm., 

 at closed end 2.6 cm.; third, length 40 cm., width at open end 3.5 

 cm., at closed end 1.6 cm. The colony does not taper greatly, and 

 may well be said to be more cylindrical than P. ailanticum atlmiticum , 

 but this one feature has little taxonomic value. Herdman (1888) 

 gives the dimensions of a specimen captured south of Australia, which 

 is probably of this subspecies, to judge from the description ap- 

 pended. They are as follows: length 36 cm., breadth at open end 

 3 cm., at widest point 4.5 cm., at closed end 1.5 cm.; the diameter of 

 the common cloacal aperture 1 cm.; thickness of the test 0.4 cm. 

 He reports also a fragment from a colony which is 7 cm. in breadth, 

 with an aperture 4.5 cm. in diameter. The total length of such a 

 specimen would probably exceed 55 cm., to judge from calculations 

 based on the relative dimensions given above. 



An irregular arrangement of the zooids establishes itself very early. 

 These then become crowded and as a result assume various abnormal 

 positions in the test. Sometimes a group of them are inclined or 

 bent over en masse; or individuals may become completely reversed, 

 that is, may be with their ventral side directed toward the aperture 



