Vou. 2] hitter —The Pelagic Tunicata. 83 
the branchial apparatus consists of a membranous partition be- 
tween the pharyngeal and atrial ends of the animal, pierced 
by pairs, never very numerous, of stigmata. Both branchial and 
atrial orifices terminal and at opposite ends; both encircled by 
lobes; those of the branchial orifice always more prominent. 
Branchial tentacles and dorsal lamina wanting. Intestinal tract 
small but never nucleaform; situated on ventral side of body, 
immediately behind the branchial membrane. Hermaphroditic, 
the gonads of both sexes always simple; ovary never producing 
a large number of ova. 
In addition to the sexual method of reproduction, in which a 
larval stage of the typical tunicate tadpole is passed through, a 
process of gemmation prevails in which three polymorphic gen- 
erations occur. 
Genus Doliolum Quoy et Gaimard, 1835. 
With characters of the family. (The genera Anchinia and 
Dolchinia not occurring, so far as known, in our area, are not 
taken into account in the diagnoses. ) 
Three species, namely, D. tritoms, D. ehrenbergu and D. mil- 
leri, are here recognized as belonging to our fauna. Whether 
certain forms of doubtful status, not now treated, belong to one 
or another of these species, more extended observation in the 
future must determine. 
Owing to the fact that zooids of the generations produced by 
budding, far advanced in development, rarely reach the hands 
of the student still attached either to their parent or to one 
another, the difficulty of arriving at unquestionable conclusions 
as to how the various forms of the different species go together 
is great. As to the old ‘‘nurses,’’ @.e., oozooids in which the 
internal organs have wholly disappeared through degeneration, 
and the muscle bands have become greatly broadened. we are not 
yet in a position to specify with absolute certainty the specific 
characters of this form in a single species of the genus. My 
diagnoses of this generation in each species relates almost wholly 
to the young zooids before the degradation of the organs has 
begun. 
