254 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



of the colony, but this is rather unusual. For the most part the 

 zooids are long and slender, owing to the extreme elongation of the 

 cloacal processes. The total length, corresponding roughly to the 

 thickness of the test, approximates 7.4 mm. (large colonies). The 

 height of the zooids is 2.4 mm. to 3 mm. The cloaca is ordinarily 

 3 mm. long, ranging between 2.6 mm. and 3.6 mm. The elongated 

 branchial basket is best defined as oblong. At the anterior end the 

 tip of the endostyle causes an elbowlike protrusion in the body wall, 

 best understood by reference to the figure. In each branchial lamella 

 there are about 36 stigmatal rows, and 17-18 longitudinal bars 

 (occasionally only 16, or as many 20). 



These numerical distinctions, according to our experience, serve 

 better than any others in demarcating this form from P. atlanticiim 

 atlanticum for in none of the Pacific specimens of P. atlanticum which we 

 have examined could we find more than 16 longitudinal bars in each 

 gill-lamella. Hitter found 15 to be the maximum number of these 

 branchial bars, in the specimens which he describes as P. giganteum r 

 but which we have regarded as of the subspecies atlanticum. In 

 the Atlantic Ocean, however, there is a rather similar form, our 

 giganteum, with nearly cylindrical colony, of yellow or bluish color, 

 with greatly elongated zooids, and whose branchial bars usually 

 number 17 or 18, sometimes as many as 20. Here seems to be the 

 clearest distinction between these two forms so long confused. 



As before noted, there are often masses of reddish pigment lying 

 on the viscera. These have been found on the esophagus and the 

 intestine, and in some cases on the testis. Often they are so distinct 

 as to be readily seen without a lens, after the wall of the colony has 

 been cut. We do not find these pigment masses in the zooids of 

 any but the yellowish colonies. In the blue ones the viscera are 

 densely opaque, and of dull bluish or gray color. The red pigment 

 may have something to do with the yellow color of the test, but it is 

 hard to see how any such connection could exist. The color of the 

 test, at least in some of the greenish colonies, is most dense in the outer, 

 peripheral zone. 1 In this region also the test-colls are most numerous, 

 which may indicate that these cells have something to do with the 

 color of the test. 



Rather characteristic of this form, is the great length of the cloaca. 

 It tapers regularly toward its distal end. The cloacal muscle occupies 

 a position about midway of its length. 



Gonads. This is another of those forms in which protandry is 

 common among the zooids of growing colonics. The testis is a large 

 hemispherical organ consisting of a variable number of lobes (18 in 

 one instance). The embryo finishes its brood-development in the 

 cloaca of the parent zooid. 



1 . Sec Herdman (1888, p. 28) to the contrary. 



