88 University of California Publications. | ZooLoGY 
an oozooid constantly occurring in our area, which is probably 
the senescent stage of this generation of tritonis. Many of these 
specimens reach a length of 125 mm., or even more, and a thick- 
ness of 7mm. This is near the maximum size recorded for any 
Doliolum. When it is recalled that the gono- and phoro- zooids 
of tritonis are likewise the largest for these generations, of any 
species, the reasonableness of the supposition that this large 
nurse belongs to tritonis is apparent. It must be said, however, 
that this line of consideration really has less weight than it might 
seem to have, since we are entirely without information as to 
the size that may be attained by the oozooids of any of the species. 
Uljanin, *84, has recorded the occurrence in the Mediterranean 
of a nurse measuring 30 mm. in length, and this he assumes 
belongs to D. ehrenbergii. The identification is, however, by no 
means certain. Asa matter of fact, in the present state of knowl- 
edge, I do not believe it possible to assign with certainty any 
oozooid, after the degeneration of its organs is complete, to its 
species; and since the degeneration is complete at an early time 
in all the species, so far as known, the difficulty of disposing of 
these old nurses is obvious. 
Fig. 25.—D. tritonis, Phorozooid. 
(ec) Phorezooid.—F ig 25. This differs in no particular from 
the sexual generation except in the absence of the sexual glands 
and the presence of the ventral process. This latter is short and 
thick, is situated in the median ventral line in the sixth inter- 
muscular space a lttle in front of the seventh muscle band. The 
following lengths of the zooids are typical: 12 mm., 11 mm., 
11 mm., 11.5 mm., 12.5 mm., 13 mm. The gonozooids and phoro- 
