38S PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
The few tubules constituting the gUmdular organ surrounding the 
intestine have tapering ends. 
■ The single large testis has the usual position in the left posterior 
part of the abdomen, and the proximal part of the sperm duct makes 
usually from eight to ten turns about it. Many of the colonies contain 
Marge tailed larvae of the type usual in this group. 
Comparing this with the descriptions and figures of the European 
and Arctic species D. variabile (Huitfeldt-Kaas), the chief differences 
seem to be that D. variabile has slightly larger zooids (2 mm. long) 
and that calcareous bodies in the test have not been observed. These 
differences do not appear necessarily to indicate that the European 
form is distinct from D. tenerum. 
Didemnum strangulatum Ritter (1901), from Kadiak Island, Alaska, 
20 fathoms, is, from Ritter's descrii)tion, evidently a close ally of the 
present species. It also has a few "calcareous stellate bodies" in the 
test in some colonies; in others none were found (Ritter, 1901, p. 248). 
Their rays are, however, described as short and blunt. The zooids 
are about 2 mm. long. The character from which Ritter names his 
species, the violent constriction of the body between the thorax and 
abdomen, occurs also in D. tenerum and in the European form, as 
Bjerkan's (1905, PI. 3, fig. 9) figure clearly shows, and would indicate 
the identity of all three forms, if it were of any value as a specific 
character. However, it has no such value, as it may be observed in 
members of other genera of this family {Lepioclinides faeroensis and 
Didemnum lutarinm, for instance). 
Didemnopsis tenerum ranges from the Banks of Newfoundland to 
off the coast of Cape Cod, in depths of from 10 to 7.5 fathoms. A 
muddy bottom seems to be most favorable to it. The European 
and Arctic species Dideynnopsis variabile (Huitfeldt-Kaas, 1896), 
which, as above stated, may be identical with it, is widely distributed 
and common on the Norwegian coast, and is recorded from Spitz- 
bergen, the ^Nlurman coast, and the Siberian Arctic Ocean, occurring 
in depths of from 40 to 180 meters, on muddy bottoms with scattered 
stones, shells, etc. A variety of it (gelatinosnm) described by Huitfeldt- 
Ivaas (1896) from Norway has also been recorded by Redikorzew 
(1907a, 1908b) from the Murman coast. 
The writer has examined specimens of D. tenerum from the following 
localities: 
Banks of Newfoundland, collected by Captain T. M. Coffin; Station 
