Pachycerianthus torreyi n. sp. — A rai 
209 
Protomesenteries. Directive mesenteries 
shorter or longer (type) than siphonoglyph. 
Second protomesenteries sterile, less than twice 
length of directive mesenteries, with aboral lobe 
varying greatly in length (long in type), tri- 
neme running to near tip of aboral lobe, usually 
(type) with several craspedonemes at aboral 
end of trineme, convoluted mononeme running 
around tip of lobe. Third protomesenteries ster- 
ile, approximately same length (type) or 
shorter than P 2 , longer than Pi, trineme much 
shorten than in P 2 with a number of craspedo- 
nemes at aboral end, mononeme relatively long 
and highly convoluted along border of broad 
section of mesentery. 
Metamesenteries . Definite MBmb arrange- 
ment ( Fig. 1 ) . Reproductive organs in macro- 
septa only. Mi mesenteries at least five-sixths 
length of column, never reaching aboral pore; 
remaining mesenteries less than two-thirds 
length of Mi in most specimens (longest mes- 
entery approximately seven-eights of Mi in 
one specimen). Macrosepta generally decreas- 
ing in length toward multiplication chamber; 
M 3 longer than M 2 , m 2 and m 3 shorter than mi, 
m 3 longer or shorter (type) than m 2 . Mi with 
trineme almost to aboral end of mesentery, 
craspedonemes scattered over most of its length, 
sometimes with an aboral lobe of mesentery or 
bunch of craspedonemes at aboral end of tri- 
neme, short mononeme (type) or none, repro- 
ductive region to above level of craspedonemes, 
hermaphroditic. Macroseptum mi with long 
trineme terminating much farther from aboral 
end than in Mi, trineme with scattered craspe- 
donemes and sometimes with an aboral bunch, 
mononeme well developed, convoluted or 
straight (slightly convoluted in type). Extent 
and form of trinemes and mononemes of other 
macrosepta variable. Bi shorter than P 3 , with 
short trineme with bunch of craspedonemes at 
aboral end, highly convoluted mononeme along 
broad section of mesentery. Other B and b with 
structure similar to Bi although bunch of cras- 
pedonemes of trineme may be reduced or ab- 
sent. 
Nematocysts (based on five adult specimens). 
Of column, atrichs 29 . 6 - 83.2 X 5.0-29.6 g 
very common, microbasic b-mastigophores 18.5- 
43.2 X 3 . 2 - 8.0 g scarce, holotrichs 42.2-67.6 
Fig. 1 . Diagram of the internal arrangement of 
Pachycerianthus torreyi. View of half the animal cut 
longitudinally and pinned flat. Approximately V2 X 
vertically, 5 V 2 X horizontally, a, Oral disc; b, actino- 
pharynx; c, marginal tentacle bases; d, labial tentacle 
bases; e, mouth; f, siphonoglyph; g, hemisulcus; h, 
protomesenteries; i, first quartette of metamesenteries; 
Pi, directive mesentery; P2, second protomesentery; P3, 
third protomesentery; Mi, M 2 , Ms, first order meta- 
mesenteries; mi, m2, m3, second order metamesenteries; 
Bi, B 2 , Bs, third order metamesenteries; bi, b 2 , b 3 , 
fourth order metamesenteries. 
X 10.0— 16.2 g rare. Of marginal tentacles, 
atrichs 24.0-36.8 X 4.0-7 .2 g scarce, micro- 
basic b-mastigophores 20.0-49.6 X 3 .0-9.0 g 
common, spirocysts 7.6-43.2 X 1.2 — 5.6 g nu- 
merous. Of labial tentacles, atrichs 24.0-33.6 X 
3.6-6.4 g scarce, microbasic b-mastigophores 
19.2- 45.2 X 2 . 0 - 8 .4 g common, spirocysts 
13.2- 33.6 X 1 . 2 — 5.2 g numerous. Of actino- 
pharynx, atrichs 24.8-40.8 X 3 . 6-6.4 g scarce, 
microbasic b-mastigophores 20.8-44.4 X 2 . 8 - 
7.6 g common, spirocysts 11 . 2 - 26.8 X 1 .6-4.4 
g very rare. Of ciliated tract of macroseptum. 
