VoL. 2] Ritter—The Pelagic Tunicata. 87 
less of a spiral, the length of the loop of the intestine being 
scarcely greater than that of the esophagus. Degeneration of 
the internal organs, with the simultaneous increase in width of 
the muscle bands apparently beginning considerably earlier in 
this than in either of the other species—D. miilleri and D. ehren- 
bergu, with which it occurs in this region. Old individuals (of 
this species, probably) reaching a leneth of 25 mm., with thick- 
ness of 7 mm., while length of individuals just before beginning 
of degeneration of internal organs, 1.38 mm. 
While the evidence that the oozooid here deseribed belongs 
to tritonis is not complete, it is sufficient to admit of little doubt ; 
indeed, there is with this, as with other species here treated, an 
element of uncertainty about the assignment of the oozooids to 
their proper species, since in no one of them have I seen the ori- 
gin either of the embryo from the egg, or the production of the 
phoro- and gonozooids by the oozooid. My chief reliance for 
the identification has been the intestinal tract. Those oozooids 
with a tract entirely similar to that of the gonozooid of D. ehren- 
bergu I assume to belong to this latter species. Similarly, those 
in which the organ is the same as that in D. miilleri, it is assumed 
belong to that species. Now it is true, as indicated in the diag- 
nosis, that although the intestinal tract of the animal at present 
under notice differs somewhat from that in the gono- and phoro- 
zooid of tritonis, nevertheless its resemblance to the tract of 
tritonis being closer than it is to that of either ehrenbergii or 
milleri, the only other species thus far found in this area, the 
conclusion that the animals belongs to tritonis seems justified. 
Another point that, on the whole, speaks for the same con- 
clusion is the character of the lobes of the atrial orifice. These 
are so low in both the gono- and phoro- zooids of tritonis as to 
render them searcely recognizable. This is likewise true of the 
00zo01d now being considered. In fact, only in an occasional 
specimen have I been able to see anything at all like lobes. True, 
the atrial lobes are considerably less easily seen in all the species 
with which I am familiar than are the branchial; but in the 
present zooid their conspicuousness is less than in the corre- 
sponding zooids of any other species. Another consideration 
that I believe points in the same direction is the great size of 
