360 W. G. Van Name — Bermuda Ascidians. 



appears quite blackish, for the zooids are numerous and closely 

 placed; in other cases they have but little dark pigment, and appear 

 lighter than the greyish test, which also contains a greater or less 

 number of black pigment cells. 



I have found this form only at Hungry Bay, where it is common. 

 A number of colonies wei'e collected under stones in the latter part 

 of May, 1901. None of the zooids appear to have reproductive 

 organs developed. 



Didemnum porites, n. sp. 



Plate LI. Figure 29 and 33. Plate LIX. Figure 115. 



A couple of colonies, the largest about 25 mm across and rather 

 thick, were obtained growing on algfe in Bailey's Bay, May 1st, 

 L901. They differ considerably from D. atrocanum, though they are 

 also of a grayish color, becoming black in the upper parts of the 

 colony. 



The test is of firm consistency, though bladder-cells are very 

 abundant in some places ; the spicules, which exactly resemble those 

 of D. lucidum described below, are fairly evenly distributed through 

 the test and come close to the surface, giving it a slightly rough 

 granular character. The apertures of the zooids on the surface are 

 conspicuous and slightly prominent. The test is opaque. 



The zooids are of good size (1.3 mm or 1.4 mm long in many cases in 

 the preserved specimen), and have a little black pigment in the 

 mantle walls. In structure they resemble those of D. savignii. I 

 have counted ten or eleven turns of the vas deferens in some indi- 

 viduals. 



Didemnum lucidum, n. sp. 



Plate LI. Figures 26, 28 and 37. 



This is a species with very small zooids (usually less than l mm in 

 length), which are slightly or not at all pigmented, forming small, 

 fairly transparent, nearly colorless incrusting colonies of slight 

 thickness. Sometimes the anterior end of the zooid is marked with 

 a little blackish pigment about the aperture and over the ganglion. 



The spicules, though varying much in size, are mostly under .<>4"' m 

 or .05 mm in diameter. They have long but not very numerous con- 

 ical points, and are distributed unevenly in the interior parts of the 

 colony, generally not in sufficient abundance to greatly interfere 

 with the transparency of the test. Near the surfaces of the colony 

 they are wanting and there are a good many bladder-cells. 



