30 THE VOYAGE OF H.M.S. CHALLENGER. 



fragment of a large Pyrosoma came up iu the trawl, which had been down to a 

 depth of 1900 fathoms. The specimen may have been captured at any jaoint during 

 the ascent of the trawl. 



At Station 69 in the North Atlantic, a large Pyrosoma, which is recorded in Mr. 

 Murray's note-book as having measured, when living, 4 feet 2 inches in length and 9 

 inches in breadth, was captured by means of the trawl let down to 2200 fathoms. 

 This magnificent sjaecimen was not preserved entire. A few small pieces were put in 

 absolute alcohol and in picric acid, and that is the material I have examined. 



Professor Moseley ' writes of this specimen as follows: "A giant Pyrosoma was 

 caught by us in the deep-sea trawl. It was like a great sac, with its walls of jelly 

 about an inch in thickness. It was 4 feet in leno;th and 10 inches in diameter. 

 When a Pyrosoma is stimulated b}' having its sur&ce touched, the phosphorescent 

 light breaks out at first at the spot stimulated, and then spreads over the surface of the 

 colony as the stimulus is transmitted to the surrounding animals. I wrote my name 

 with my finger on the surface of the giant Pyrosoma as it lay on deck in a tub at 

 night, and my name came out in a few seconds in letters of fire." 



These various fragments (from Stations G9 and 133) appear to belong to the same 

 species. 



Tiie exact shape of the colony and the condition of the common cloacal aperture 

 are unknown, but the appearance of the outside of the colony is very characteristic. 

 There are, at least in the fragments preserved, no large processes from the outer 

 surface of the test, such as are known in the other species of Pyrosoma; on the other 

 hand, a large number of closely-placed, small, sharp-pointed spines are found all over 

 the outer surface of the colony (PL II. fig. 9). These have their points all directed one 

 way, towards the dorsal edge of the Ascidiozooids, and so they give the surface of the 

 test a scaly appearance, quite unlike that of the other species of Pyrosoma. As none 

 of the fragments contain either the closed end of the colony or the common cloacal 

 aperture, it is impossible to say which way the Ascidiozooids are arranged in the 

 colony ; but if they are placed with their ventral surfaces towards the closed end of the 

 colony, then, as in moving through the water the closed end goes first, the spines 

 placed on the ventral edges of the Ascidiozooids with their points directed dorsally will 

 no doubt be of service as a protection to the branchial apertures which they overhang 

 (PI. II. fig. 10). Besides these spines, which are distinctly related to the Ascidio- 

 zooids, there are also smaller ones scattered over the surface of the test between the 

 Ascidiozooids. 



The test is very soft and gelatinous, although thick ; it is perfectly transparent, 

 and the yellowish tint of the colony as a whole is due to the Ascidiozooids, which are 

 more opaque than the test. The Ascidiozooids in surface view occupy rounded areas 



^ Notes by a Naturalist on the Challenger. Macmillan & Co., London, 1870, p. 574. 



