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PI^OROIIIS ARCHITECT A.

Dissertaticn,

Snbmitt'^a +-g the Board of Univf;rsity Studied of the
Johns riopkins University ixi confonrdty with the require
merits for the dee; re e of Doctor of Philosopny.

By
Rheinart Parker Cov/les.

February, 1904.

/iCs^'jl

7t«.. off.c

_ PH0R01II3 ARCHITSCTA;
_ ITS LI7E HISTORY^ AIIATOI^ilY AJID BR I5E^DIJ[G JW ^I TS_5__

During the sumraer of 1901, I bewail thfi study of Phoroviis
architccta at Beaufort, ITorir, Carolina aiid I continued the same
in th.e suirurar of 1902. I v/i sh to express my ti:anks to the
Thiitel States 'Fish Commission for the privilege of v;o rkin^i in
their station at Beaufort #iere all the couvGniences necessary
for scientific invcstijjation are at hand. To Prof. H.V.V/ilaon,
Director of the station in 1901 and to Dr. Caswell Gravo , Direc-
tor durin^ 1902, I am indebtea for many kindnesses, which I
take pleasure in acknovv'ledjrinc

VfTiile the study of the live material was for the most part
dene at Beai^fort, the rest of tne work was pursued in the Zoo-
xogical Laboraoory of the Johns Hopkins University, and it is
a pleasure to have the Ofportunity of tenderinti irc sincere
thanks for valuable suggusL i.^ns aaid friendly encouragement to
Prof, W.K. Brooks.

Since the discovery of Phoronis hl^^.crepia b: Wright in
1856, the affinities of this most interestint; genus have been
more or less under discussion. Different investigators have
sought to ally ti.e Pnoronidae with the Bryozoa, the ErachJopoda,

..'■VI

the Sipunculida and other t,roui;s.

Houle (20) thiiiks that the Phororjilae shoula be placed
next to the hr-jozoa- in a natural classification. He aces not
consider that they havo any affinity to the EnterOiPneusta but
from a study of the early statics of devGlopment , he finds that
they are related to the true Chordata (Tirnicates and Verte-
brates). Ke says, "lembryon de Vertebre est uiio Trociiophore
renversee, "

Lankester and Kclntosi; are incliiiCd to consider Phoroiiis,
Cephalodiscus and ^habdoplcura as related fonris ivnixc Harmer
(7) rtic'kes a comparison uf Phoronis with Cephalodiscus and
thinks tnat perhaps there may bo some affinity.

Masterman (15-16) in a series of papery maae a compariaon
0 "•" the Acti no trocha- larva of Phoronis v;ith Balano^lossus and
its larva ai^d also witn Cephalodiscus, Ii; tris paper, he ar-
rives at the Conclusion ti'a.t there is a close ^^enetic relation-
ship between the Phoroniaae, Balaiio gloss us and Cephalodiscus,
Since the appeararxce o f Master Jiian's papers, Ikeda (9) has in-
vesti^^atod the development of Phoronis Ijimai and has made a
careful study of several Act ino trochae found in Japanese ;vater3.
Shortly after this, Lont^champs {!'<,) published a comparative
study of the early development of several species o -^ Phoronis
ana also o -^ several species of Act ino trochac, ,:,ivinc a very care-
ful critical r;esume'' o f^ the work done by dif-f'erent investigators.

(3)

Menori (17) has lately publishea a short paper on tlr^ Actin-
otrocha ^ in wiiicii he considers t,'ne Phoroniaae to be related to
the Choi-aata but tr;inks the relationship is to bo traced tnrou^i
a fonn like Rhabdo pleura.

I bc^BM the study of tne development and anatoriiy of Phoron-
is architecta before the publication o "^ the last four papers
mentionea; aiid when they appeared I was almost aissuaded fl^'oiij
continuiiif- my work, Hov/ever si'uce there seem to be s^^ecific
di'^ferences a"nd since there are several disputes points in the
development, it seems best to publish the resultd of mj study.

It is hardly necessary to enter into a historical account
of the work that h^s been aone on the development and anatomy
of the Phoronidae since there are several papers vhich. have re-
viewed tl;e subject exhaustively.

lie t hods .

Most of the material, eg-,3, larvae and adults, were fixed
in a saturated solution of corrosive sublimate, to which r.ad
been added two per cent of ^jlacial acetic acia. A fres). so-
lution v.'as made as soon 8,s ti.e fine white precipitate appeared
Which is usually present in old solutions. This fixin^ agent
gave very ^ood results. Material fixed in Perenyi's fluid was
found more valuable in some few respects thaii tlie acetic subli-
mate. V/hen setrmcntaticn staf^^es v;ere treateav/ith a five per

(4)

cent solution of formaldehyde, tne bias tome res stood out al-
most as distinctly as in tne liviUi, material. The larger
species of the two Actino t -"ochae , founa in Beaufort Harbor is
much more active than the other, and v/hen it comes in contact
with the fixing, fluid, the preoral lobe is bent upward into an
unusi'9.1 positiori. Consequently a few drops of four per cent
solution, of muriate of cocaine in fifty per cent alcohol was
added to the v/ater containing the Actinot rochae. After this
treatment the Actino tro chae died in their usual form when put
in the fixing fluid. ■Plemning" fluid as well as the acetic
sublimate was found to be a \er-j valuable fixin^ agent fb r the
Actino tro chae, Keidenhain's iron haematoxylin was used in
staining sections o^ the adult and a secondary stain of alco-
holic eosin or rubin gave verv good results. The most sat-
isfactor-y stain for sections of young larvae aiid Actinotroch-
ae was found to be a solution of saffranin in anilin water.
Since it was very desirable to make a study of tiie adults
throughout the year aijd as i t v/as not possible to reinain in
Beaufort for this purpose aurin.^ the winter and spring months,
the author nad sfecimena collected and sent to Johns Hopkins
University at dif-^erent times. Here they were platted in aqua-
ria filled with sea water, v/hich '.vas kept in tjood conaition by
a rich growth yf diatoms on top of a layer of sana, ITot only

(5)

did the diatoms keep the water from bocomi-a,, polluted bwt they
also afforded abundant food for the Pnorcnis so tiriat healthy in-
diviauals v.-ith their lophophcral tentacles fully expanded v;ere
continually at haiid f o r a live study. The author is much in-
debted to Dr. Caswell Grave, the originator of the diatom meth-
od in rearing Echinoderm larvae, for the use of his aquaria.
Drew's modification of Patton's method for imbedding and oriont-
ing f^SES was used with fairly i.,ood success, althougir; a large per-
centage of the embryos were broken durin^^ the process. Most
of the em.bryos were cut into y'^ctions thre^yO thick but for
so0ie points sections two yO' ti.ick were used,
Br e e d i 'i^i^ ^ Habits. _

^aidrews's (1) observations on Phorcnis architecta bring him
to the concliisicn that either the sexes are separate in ti.at
species or that if the individuoils are hermapiirodi ti c the male
and female elements mature at different times. I lictve exam-
ined many specimens during May, June, July, August, Septej;iber
and October, both by ineans vV sections ana wl:en alive. During
this time in no case have 1 found ovaries arid testes occurring
at the same time in an individual. There is no doubt ,ho wever ,
but vvhat ovaries and testes occur together in the same individ-
ual in P. ^ustralis. Benhain (ir) has observea this, as I have
also in material sent to me by Mr. Ikeaa.

(6)

During the month of January the feritoneal tissues sur-
rounding the bloou caeca is very abundai.t but as a rule at this
time no e^t^s or sFermatoaoa arc founa to be present in it. In
one indiviaual out of some twenty or thirty a few ovarian 6(^,^3
v/ere found, iiowever. All of these specimens collectca in Jan-
ua.ry were without lophophoral ort,ans and i kcrt n.any o "" them in
aquaria until t..e 1st of May, At this time lophophoral or-t^ans
began to make their appearaiicc in some, v,i;ile in others they were
absent. In ail the specimens, nov;ever, eitlier ovaries or testes
were present as was also the case in specimens collectea at Beau-
fort in the early part of May. 1 sliall liave so.uething fur-
ther to say in reference to tjie lophophoral organs ai£i their re-
lation to the breedin>^ season under the section v.hich aeals v/ith
tiie structure of the adult.

The breeding season of Pi-.oroiiis architecta exte^^ds f^om
LTarch or April to ITovember or Decenber, Ikeaa (9 ) has stated
that "the breeding season of Phoronis IJimai raiiges ti:roUfc,n about
half of the year, say from llovomber to June or July". There
seems to be a surprising difference in the time of breeding be-
tween these two species. The Actino tro chae of Phoronis are
found throughout the suruirier and autumii but they are especially
abunaant during August and September, Ixeaa has suggested that
Phoronis annually "cnanges its generation." It does not seem

: )

(7)
probable that this is the case for Phorouis architecta because
full sizea actults are fouua througtiou t the year in Eeai'.ftrt
Harbor am I have sr;eciiTiena in tr.e laboratory at JoiUiS Hoi- kins
University which are fifteen mouths old.

Durin^-, one low tide in the sunaiicr ana autumn, I found it an
easy jnaiter to collect from 100 to 150 specimens of Phoronis
architecta. About one half of these vvoula usually be with male
reproductive organs and the rest with female reproauctive ori_,ans.
The Phoronis were j. lace a in glass crys talliiiing dishes ana af-
ter about twenty-four hours many of the indiviauals began to
lay, usually at night, but the eggs were not retained among
the tentacles in a mass as describea by most investigators , but
were sv/ept gently away from the lophophoral crov;n by the cilia-
ticn on the tentacles axid on the anal region so that they set-
tled near by on the bottom of the dish. Sometimes, iiowever,
the newly laid eggs were carried up ana dovm the tentacles in
currents caused by the cilia ar.a occasionally a. few eggs v.'ere
found groi'fed near the tips of the tentacles, bein.v hela there
loosely by a sraal] quantity o-f" mucus-like material. At no
time, however, were eggs aixi larvae ag,,regatea in definite mas-
ses as aescribed by Ikeda (9) nor were they brocdea airong the
tentacles as Ma^teman (IG)has observed in tne cas« of Phoronis

Buskii. That efZi;3 and embryos v;e re not Ibuna by Loiif^cnamps
amonc the tentacles of PhooDnis a'Helgolavid is no doubt due to
the fact that the same habit prevails in the above form tl:at does
in. Phoronis architecta,

V/hile the adults were laying, they were examined under the
compound iidcroscope. They showed lar<:;e nugibers of eg-^s v/hj-ch
v;ere floating; freely back ai/a forth iii the body cavity as the
aniiTial contracted and expanaed. Sections of adults iii this
conditJcii show that all these free eggs contaiiiOd t]:e first po-
lar body spindle. At intervals of about one iTiinute, an egg is
extruaed '.vith coiisiderable force from the nephridial openiiig
aiid in no case are the eggs at tnis momeiit witri polar boaies.
The wall of titC nephriaial ridge is transparent eiiou^x; to see
the eggs as they slip tnrou-j^n the larger part of tl"-e liepr.ridium.
Hia-.ile passing through, the eggs are pressed by tj;e walls of the
organ until they are about twice as Ioh:-, as broad, CFig.l) The
fact that ^hcrcnis architecta does not keep its eggs in masses
within t}ie tentacular crova-i together with the fact that liioat of
the individuals lay their eggs at about the same time of nigj:it,
iiiakes it possible to preserve any one stage in the development
of the embryo in sufficient quantity for a tiio rough study.

_ 2'9 r? i li ?a t i£iij,
Ikeda (9) aiid Longci^'Jiixps (12) made the observation that the

(9)

egrs in the body cavity of the -^areut si;oweci the spiudles of the
first rolar body. This 1 -l^ouria to be the case iu Phcrciiis ar-
chitecta. C^ig.l) Eggs in the nephridia were founu to be in
the sarrie stage and in neither case was there any sign of an en-
ti^riiig spermatozoon or a n.ale pronucleus. ("Fig.l) There Is no
doubt of the fact that in Phoronis architecta the sperir^to sioon
does not enter tl:e egg until tJ:e latter has been expelled from
the nephridium. Ikeda observea this fact for Phoroiiia Ijirriai,
Segmen tat ion.

The eggs of Phoronis architecta while still in ti:e body
cavity are somev/hat irregular in shape and, as mentioned above,
are aecidealy so while passing through the nephridiuiTi. However,
a^ter they are laid they become almost perfectly spherical aiid
avera,;e 100/X/ in diameter CPig.g) thus measuriiit, the same as
the egg of "Phoronis ao l.aples." (Longciiamps (1£) ). The egg
is verj opaque, beint. heavily laden ,vith small yull: granules.
It is surrounded by a delicate ms.7ibrane whicii, hov;ever, is not
vor-j conspicuous being closely applied to the surface but after
f2»-^lxiiiaticn, it separates to some extent. (Fi^.^. 2)

Observations en the segmentation o f^* the egg of Phoronis are
conflicting. This part of the development o^ Phoronis seems
to have been treated hastily by most observers probably because
it la 'difficult' to obtain sufficient material for its study.

(10)

It is agreed that tl:e segmentatiori is total, Toettincer (o)

ard '^'. Schultz (21) claim that the aegneii tat ion is unequal.

(5)
Caldwell^ says that in ti:e four-cell stage two srualler clear aa^d

two larger opaque cells are f resent, Masternian (16) finds tiiat
in the for^r-ecll stage the bl astonieres taper toward one pole
and that this results, v/hen tl.e third f.irrow appears, in the
upper four being less in bulk than the lower four, Masterraan's
description, ^ find, applies to the eggs of Phoronis Australia.
Ikeda (9) did not discover any appreciable difference in the
size of the blastomeres until tne eignt-ccll sta^o. At tuis
time , he says, "it will be seen that tne upper four blasto-
meres are very slightly smsJlcr tiian tne Ic.^r fj^'-, «

In Phoronis architecta the •f'irst cleavag? plane is merid-
ional and usually divides the egg into tv/o practically equal
blastomeres ("Pig. 3) altr.ouj-h sci/ietimes the division is decid-
edly unequal, (Fig. 4) The cleavage fi;rrow begins in the re-
gion of the polar bodies. ("Pig. 5) After the completion of
tiie first cleavage and sometimes before, the first polar body
divides. (Fi^.o) In "^ig.b ia seen the reconstruction of the
nuclei after the first cleavage. Immediately before the sec-
oua cleavage the two blastomeres uhich were closely applied
to one another after the first cleavage come to overlap.
About fifteen minutes aftc*- the firat cioavage, thn second

(11)

cleavage takes ^1^^^. I* it. rruri diorial ana at ri ,:ht aii^ieB to
the ^^■i^st, d.i vidian, the tv;o equal blastcmcrcs into four equal
blastoiricros. As Ikeda has obsorvca the ciuavat^^ dues not oc-
cur si.Tiultaneously in bo tn biastcmorcs nor aoes it in later
cleavagv-t*. {."^J-'S* ^) '^^'^ blastoKiere;:3 of th^c four-cell staf^e
whichi at -ft rst overlapped soon become applied to one another so
that the two meet in a cross fUrrow. C^ic.^) Shortly before
the third cleava^^e occurs the cross furrow disappears and the
blastomeres come to overlap, Tr.o third cleavafoC takes place
fifteen minutes after the secoiiu cleavage and it is equatorial.
The blastomeres become drav/n out into a more or less ovoid
shape and, as division takes place, the upper four olas tome ^^ij
become rotated in the dj. rection of tl:e hands of a v/atch, (■Pijj;.9)
The eigh^t blastomeres are approximately the same size as a rule,
and there is a siriall sedimentation cavity present which from now
on persists. CPi^.lO) The three polar bodies are aistint^uish-
able at this statue sometimes within the blastocoel ana sometimes
^n the surface oV the blL.stomcres, The blastocoel is Oi^en at
the animal d,nd vegetal poles. The sixtccn-cell sta^e arises
from the eight-cell stat,;e by a meriaioi;al division of each of
its blastomeres but they ao not all divide simultaneously,
(■pig.ll) alti:ou(;h the difference in time is verj slight.
Ancr trio sixtcen-cell stare T could not follow t:;e individual

blastoineres. The aivisicii takes placo rather irre£ularly but
tixe blastomeros are all about of the saiQe siiie.

The so-callea "biastocuel pore" observed by Ikeaa (9)
1 have also found o ccaaioiialiy in youn^ blastulae but I aw in-
clined to think tiiat it does not appear in a definite place
and that it is variable in occurrence, (■Pit;,s. lii-13)

Two i.ours after the first cleavaj^s the blastula is com-
posed of seventy or eighty cells and it is still enclosed in
the egg membrane,

'P'our hours later the membrane disappears ana the ciliatea
blastula begins to swim, (Fii^.l4)

The blastomeres v/ere so muci: alike -and so uniforn in si^e
that I was not able to trace tneir individual nistory. It
vrould seem probable from Mas term an' s y/ork on Phoronia Euskii
(16) that the cell lineage migi-,t be follov/ed in that fb na, -^or
lie finas considerable difference in the size o ■*' the blasto-
meres in the early stages of" cleavaa,e at least,

Tlie apical pole of the ciliatea blastula is provided v;i th
long cilia, ("fig, 14) The nuclei are situatoa nearer tlie out-
er ti:ari the inner surface anu tne inner ends of ti.e cells are
filled with rather aense ^^ranules. In the segmentation cav-
ity are ^ound tiie so-called "corpuscles", which have been ob-
served by most investigators working on the early stages of

(13)

Phoro-ais. Caldwell's (ca) viev; that tney are not mesoderm
cells is undoubtedly correct. My o bservatioiiS agree v/i th
those o-f' Ikeaa (9) for I find the "plasmic cortnacles" much
smaller than any of the cells of the blastula a^.a do not fina
tnem with nuclei. In Phcronis architecta they do not appear
until the late blastula stat'C (ng.l4) at which tirue the in-
ner ends of the cells are aensely i^ranular. It seems very
probable that the corpuscles are pushed cut from the densely
granular part of the cell aiid that as Calawell and Ikeda have
held they are an extra supplv' o i' iiouri shment ,

The blastulae, ^astrulae and youii^ larvae o ■!" Phoronis ar-
chitecta are quite similar ijx appearance to those of Phoronis
d'Helgoland whicii Lont^champs (12) has figured. Tiie develop-
ment is more ret,ular than that of most other species vr.ich; i o
probably due to the fact that the eggs and embryos are not har-
bored in the tentacular c-u.vn,
Gastrulatioii ana "Purth.er Changes in _t 1 \e T'orm of the Larva.

In the blastula, v/hich has just be^un to inva^jinate, the
invagination is eccentric thus i^ivin^^ the first indication of
the bilateral symmetry of the larva. This is further empha-
sized in the young gastnila of Phoronis architecta by a thick-
ening 0*^ the ectoderm cells, v;l;ich becomes the gan^^lion of the
Actinot rocha. The cgIus composing th.is thickcnin,- of the cc-

(14)
toderm are at thn apical ^ole in the talastula ana thoy bear lon^
;ilia but as £astn)lation takers place ana as tiio embryo elongates,
the thickening comes to occi:p:' '^ position nearer the anterior
end of the larva. (Fi^js. 15-15 ( a) -15 (b) ) As far as 1 am able
10 JudGC froni what nas been v/ritten, the ganglion makes its ap-
pearance much earlier ir. Phoronis architecta t nan in other spe-
cies, althouH- ?ioule (20) fi^'-res the "plaque cephalique" at a
rather early sta^e in Phcrcnio Sabatieri. The chan^-es which
take place in tiie shape of the blastopore are mucn like those
described by other investi^^ato rs. At the bej^innin-^ of ^^astru-
lation tr.e blastopore is wide open and circular in outline.
The lateral lips of the blastopore then t^radually d.-av/ togetl;-
er in tne posterior re[.:ion encloaini^ that part, of the wall of
the archenteron between tncm (Fi^;. 20(c) ) which becomes a solid
mass of colls continuous with tj.e colls of tr.e fiisod lips of
the blastopore. ( figs. ie(d) -lb(e) ) The cells of tne solia
mass are of the saiiiC character as those o"^ t>.e wall c/-^ the ar-
chenteron where th.e blastopore is open. They are quite gran-
ular except at the periphery where they project into tae cavity
of tne blastocoel aiid tneir nuclei are quite indistinct. Both
of these facts are cnaracteri stic of tne cells making up the
archenteric wall. ("Pi^. 16(c) )

As a result of the closing up of ti.e ulasto^ore posteriorly

(lo)

tlie blastopore becor^es oval in shape ana an incti cation of a
veiitral furrow, first observea by Cald'.vell and callea a "prim-
itive groove", appears. In Phoronia arciiitecta t ni a groove
is only to be seen in one or two sections t^ack o "^ tn e blasto-
pore aftet" which tne ventral surface is convex. ( Fij^s . 18 (a) -
20(c) ) I was unable to make cut a "primitive st^-eak" as de-
scribed by Caldv,cll. (oa) The irastm.la v.-iiich is at first cir-
cular in horizontal section becomes slightly eloiitjatea vrhen
the blastopore takes on an oval shape.

Gradually ti." blastopore lips close up r£,c "-e ii^t'^'-io rly
until tne blastopore becomes cii^cular in outline but much smal-
ler tiiaii it was 0 rij_.,;inally. At the same time tne anterior
end of tl.e larva bej^ins to bend in a ventral direction aiiu the
archenteron become o clonic ated posteriorly. (Pi^j.^O)

llo'.v ti-ie larva inc ""eases slit,ntly in lexu^ii: (''^i;^. 21) , the
blastopore assumes the fo nn of a transverse sxit, tliO anterior
eiid bends -farther veiitrally and the posterior end o'^' the ente-
ron becomes aj-i-lied to the ectoderm at the posterior end of
tne larva. (Fi^.21)

lly observations en Pr:orcnis architects ag^eo with the de-
scription of Masterman (16), Ikeda (9) una Lon^caamps {12) in
rej^ara to the closure of ti;e lips of the blastopore and the re-
sultint; chan^^e in the shiaje 0-^ the lattery but I do not think

(16)

tnat in Phoroiiis arciiitocta ti;e aefinitiv^ blastoporf^ is jusnea
fartr.cr- ^i.terior-ly b;- ti.o special activity iu ts^e posterior re-
gion of tne blastopore as Ikecia has fomi6 to bo the case for
Phororiio IJ irriai . I consider the aefinitive blastopore to be
represeiiteu by tic anterior part q-^ the wide circular blasto-
pore of the yoTni(_, i^astnjla. The chan£o in position of tne
blastopore with reference to the anterior end is a';.e to an
elont:ation of i-tie posterior portion of tne enibryo and the ven-
tral flexure of its Ulterior eiiU.

My studies on the aevelopmevit o"!^ Phoronis architecta
lead me to aj-jree v.'ith Ike da ana Lontichamps as to the fate of
the cells in the posterior part of the blastopore and as to
the eotoderrrxal orii^in of the "posterior pit". The cells of
the posterior part of the blastopore become invae,iiiated by the
closure of the blastopore lips and fo na part of the ventral
v/all of the enteron, wi:ile the "posterior pit", whicii appears
in Phoronis architecta sliortly before the de^^initive blasto-
pore is fonned, is of ectodermal orij-in and has no apparent re-
lation to the ventral iV;roove. As Ikeda (9) has statea, the
pit is the bejjinnin-, of the nephridiuiii of the Actino t rocha.
In a recejit paper Masterman (16a) says that he has found tne
"posterior diverticulum" both in larvae of P. Buskii and P.
hippocrepia aiid tiiat he consiaers them to be the anla-^e of
the nephriaia.

(IV)

"Po nnat i o i^ o f _ 1 1 . e_ Me s o cl e rm,

There is coiisiuorable ai+'ferei.ce of opinioii amoJiL; those
wiio nave iiivestit^atea the einbryolot^y of Ph.)roiiit; as to ti.e ori-
gin of the mesoderm aiid there seem to be iiO two v/iiose ucacrip-
tioiid atiree^altr.outh Ikecta (9) ana Loiii^cuixmi,s (1^) in their re-
ceiit papers ai-ri ve at tiie sarue coiicliisioviS , {^jue rally apeak-int^.

I cLtu cciiViiiced froi:! ncj ov/u dti:ay o f the e^^^^s ana larvae
of Phoronis architecta ana tnoso uf Phoronio Auat'-cilis that the
great ai "Inference in the orit^in of tr.e aiesoaerni as Roule {kO}
and Masterman (16) see it, is auc, in a gi^eat part, to dif-f'er-
ence in the larvae t heiaselvos,

Tne eg^vs and embryos o *' Phoronis Australia, for 'vi.ich I
siri a^vcn inaebted to Mr. Ikeda, are vc ^^y similar in appeara^^ce
to those of Phoronis Euskii, jutii-Ziiii^ from Masterman's fi<2;ures
(16). Sections o ^' the e^^us and larvae of the former show the
aevelopment to be of tne same i:,Ciieral type as that of' Phoronis
Ijimsd "'iiicn Ikeda (9) r.as aescribea.

The etjC^ ana larvae of Phoronis arcnitecta are consiacr-
ably different from those ms.ntioned above. They are more re^^-
ular in form, the blastocoel is much mo ro spacious cina tne cell?
ti.emsnlves are more re^^Tilar in shape and arraij^cmont . Tuey are
most simixo,'- in appearance to the early sta^^es o " Phoronis 3a-

(It)

batieri stvdiea aiia figurea by Roisle (£0) end ti.ose o ^' Phorou-
is d'Helt-^olana -^'itnired by Loi^t,, champs (1£).

The foniiatioii o ""^ the mesocierm begins ii. Phoronis architeota
as sooii as ti-.o flatteried siae of the blastula bejj:ina to i-,astru-
late. In a fev; cases, rouna blastulae aro fouria, wi ti:in Ij:o
blastocoel of v;hich, are rati;er lart.;o i^ranular ar.herical boaicy
mvch larj^er than tie plasKiic corpuscles aescribea above. Each
o"^ these contains sx. o^a-'j^ve body wiach takes saffraxiin stain
••i^-'iti. re>aainess. A comparison of these bodies witn the nuclei
of ti.e cells of the blastula wall convinces one at once that
they are not nuclei. In i^i;^, 14(a) ^ btc-^jcn tij"out,h such a
blastula is si.OvVix iii '.vhici: these bodies are seen vathiii the wall
of tne blastula as v/ell a.s insjae the blastocoel. ThiCy are iiri-
bcddcd in the v/ali v.ithout reference to tr.e liiui ts of tiie cell
aiid usually occupy the v/idth of two cells. Tne cells ei.closin^
these peculiar bodies do not aiffer from tna cells surrounding'
them in that re^^ion ano eacn has its own nucleus. These bodies
are not the cut e^.ds of amoeboia processes which Calawell (5a)
and Roule (£0) observed, for such processes ao not occur in tne
blastulae of Piioronis architecta. I am unable to make any pos-
itive statement as to their- fate but it is ve^-y probable tx.at
they break up into the smaller plasmie cor^usclea. Sucn boa-
les as tne former mi^^nt easily be mistaKon for mesoderm cells

(19)
aiid I suspect that ti;e"meso dejrm cells" obaorvoa by "^oettiii^er
(5), Metschnikoff (1£) aiirj E. Schulti (21) in the rouna blas-
tulac were of tr.c same cr.aracter,

yrom my ';;orK oi. PhonDnis architecta I am able to coufirm
the view of Mastermaii (16), Ikecla (9) aiia Loij(_^ci. aiiif s (12),tl:al
the mesoderm arises from the eiiaodenr!. Caldwell (oa) also
holds that the mesoderm arises from the eudoaerm assumiai; that
the "posterior pit" (nephridial diverticulum) vAiich he coiisiders to
be one point of orii:iri of the mesoderm, is of endodermal or-
igin, Roule (20) aerives most of the meaoacrm from the endo-
derm but also cotiSidors tne "banaelettes mcsoblastiques" v/liich
Schultz (21) first pointea out to be the same as the posterior
diverticulum of Caldv/ell, as giviii;^ rise to mescaerm.

As is seen on referring to "Pig. 15 the flattened part of
the wall 0 '■ the blastula has become more than one cell tl^ick.
In fact, active coll division has taken place. Yet most of
these cells are acstined to become the wall of the arcnenteron
and only a fov>r are to t:,ivG rise to mesoderrrj. Careful exam-
ination of many sections fails to sho^v that nesoderm cells ever
have thej r o ""igin frojn tixO aorsal surface of the arc.'.ej.teron.
In thi< respect the development of Plioronis arciiitecta seems
to agrf^e -"ith th^at of Phoronis Kowalevskii as aescribea by Cald-
well (3a) and Longchamps (12) a.nd that of Phoronis Euskii .vhich

(20)

Mcttit.eriaan (16) inveatigatea. nnly tiiat f o rt ion of t'.c v;all of
the ^ixstrula v/hich forms tiie outiiiK^ cf the blastopore is cap-
able of a.ivin;.: rise to luesoaerm ii. Piioronis architect a ana as
in the form studieci by LoiiticLamps (12), the aixterior and later-
al borders of tne blastopore are rnost active in this process,
(^igs. 16(a) (b) (c) (d) (e) (f) ) Most of tne mesoaerm is prolif-
erated from the aiiterior eiid of the arch evit eron, and the power

of r>"oduciriij the same seerrs to diminish gradually towara the

in
poste'-ior end of the blastopore lips those gaatrulae v/here the

round blastopore is just beginnin,, to close up. (Figs . 16( a) (b)

(c)(d)(e)(f) )

The mesoderm cells are very amoeboid in character and are
often seen in living specimens and sometimes iii sections send-
ini-, out long pseudopod-like prolongations v^i.icii become attached
to the walls of the gastn?la. Ey means of these afi:ioeboid move-
ments, they are able to crav/l up the walls o ^ the blastocoel.

1 was urable to make out any structure jn Pn^ ".n" o archi-
tect a v;nich I could interpret as "archei.te ric diverticula" such
as fignjred by Caid./^ii (3a) and Ikeda (9), ■Pig.i6(c) ndght
be inter^.'-etoa us showing these diverticula but the condition
there is hardly different from the arrangement of the mesoderm
c .xj-s ..nlch are being pustiea out into the blastocoel in front
'^f the blastopore. (^igs. 16-16(b) ) Caldwell first observea

these atrvcfjrcs in the castrulac o -^ Phorcrii::^ Kowalevskii but
Lonj^chajnts (1^~), wi.o i^as receutly carefully stuaied. tne same
bpecies, has been unable tc find them, Ikcaa (9), hc.vever,

'inds very definite aivcrticula in the gastrulae of Phoroids IJi-
iTiai but he fii-aires tliem as being in tiie region of the blastopore,
'.vhile according to Caldwell's (3a) figures, tney are found
posterior to tne d1 as to pore.

Let us return a^ain to t::e mesoderm cells which lie anter-
iorly to the blastopore, ThOde amoeboia celo^s unaoubt edly r:.ul-
tiply v.hile iii the bias toco el and in a j_astrula v.he re tr.e blas-
topore lips have closed up somewhat so as to give an oval out-
line to ti:e blastopore (Fig, 16(f) ), these cells have becorae
arranged into a definite sac- ( '^''it^s. 19-ijO (a) ) which is later
to fomi the linin^-. of U:e i.reoral lobe, Iii no ease was I abxe
tc fina ti;e loaat liidication cf an aiiterior unpairea divertic-
ulum which Masterman (16) uc^yo exists in the gastmlaof Ph^-
ronis Euskii. At ti.is stage the cavity o f tne sac is small
and is present only in lY-ont of the blastoporri. The v/alls
however, are extended on each side into a lateral cora of mes-
oderm cells which lies in the blastocoel at tnc side of the
blastopore. (Fig. 16(f) ) Soiae of tne cells of tne dorsal wall
of the sac. sem out pseudopodia vAiich attach themselves to an oc-

todern.al thici;eni_ng and this thici-emngwi H become the ganglion

(2k)

of tne Acti notro Ci:a. (i^ii_;.19)

The above coi/aition contiiiueo until tne oval blastopore be-
comes smaller atiU rouna in outline ( Pi t,s . 20-20 ( e) ) which chaixj^e
is also accomFanied by nirther growth of the eiiteron in a post-
erior direction nntil it almost touches the end of the larva.
The cells of the tv/o lateral cords of mesoderm have now in-
creased in number, have arrai^ed themselves so as to enclose
a cavity, continuous with tno cavi ty of the anterior one de-
scribed above and have become attached both to the lateral ec-
todermal wall ard the lateral endodGrinaj. wail, CFit^, 20(b) )
Anteriorly ti.is safe , which is now horse-shoe snape (Fi^c. 20(e) )
is still only attached to the gaxit,lionic thiciceninc and tiic ven-
tral ectoderrral wall. ("Pig, 20) The conditions whicli I have
just descrihea arc not due to the siirinJcage of ti;e mesodermal
lining away from ti;e wall of the larva for the t raiiS parency of
tije livin^, larva maJces it possible to see tne fomation of the
mesodermal sac , I have followed this formation, stop by step
maiiy times in the liviii^^ gastrula and larva as well as in sec-
tions and surface mounts.

As the anterior end of the larva bends fartiier vei.trally
and becomes a definite preoral lobe, the round blastopore as-
sumes the shape of an oval with its major axis transverse to the
long axis of the -larva. The posterior part of ti;e larva increas-

(^3)

es in leu£th sixA the eviteron send out a poaterior diverticuluiri,
the beeinnine: of tne intestincil caiial, v-.ose blinc* ena fuses
witii ti.f^ ectocieriri of the posterior ena of ti.e larva. The v/alla
of tl:e mesoderinal sac become applied to the walls of the pre-
oral lobe aiore generally, U;us fonriinfj a definite raesodereial
epithelium ^^o r the cavity of tiie preoral lobe. ( "Pi gs. 23-21- 2.k)
Posteriorly, as Masterrnan (15) has described, for the fully de-
veloyeo A^ctino tro cha, the cavity is produced "iii'to tvra horus run-
ninj:, back laterally" (Piij. 22(a) ) but as yet there is no com-
plete mesodermal linin^- in the cavity back of this. ("Pigs. 22
(b)-(c) ) The posterior wall o^ thie mesoderraal lining of the
preoral lobe forms a definite septum (f'igs , 21-21(a) ) but it
is not as yet, at least, composea of tvjo layers as Master.nan
finds in thiC older Ac tino trocha.

While tne above chai;ges have been takin^, place in the pre-
oral end of the larva there has also been sor;.e c hankie in the
postoral region. It is seen from "Figs. 16(c )- (d) - ( e)- ( f ) tjiat
in the young gastrula with the large circular blastopore , meso-
derm cells are being pushed out into ti:e blastocoel alon^ both
sides of the arcnonteric wall back almost to ti.e posterior bor-
der of the blastopore. At this stage I have sometimes seen
large spherical cells with rather small deeply stainin^; nuclei
floating freely ^n the blastocoel. T^ig. 17(a) ) These cells

(24)

have their origix. in the wall of the archentoron (Fig. 17) and
are quite di f f eront from the bodies found in th-s blastocoel of
the blastula. Thoy imve a definite nucleus and they seem to
be similar cells to those founci by Ikeaa in t^ie larva with one
pair of tentacles. They certainly do resejJDle the blooa cor-
puscles found in the older larvae only they are considerably
lar^^rir, Ikeda (9) carao to the conclusion that these cell^?
were the "jiother cells of blood corpuscles which aro founa as
corpuscle-masses in the collar cavity o "*^ the Ac tino troclia" .
Since the publication of his paper, Mr. Ikeda has written me
that he considers his theory concerning the fate of these cells
to be incorrect.

These cells are easily di stinjjuishable from all other cells
by the fact that tr. ey are larger and that tiie cytoplasm does
not staixi. They have a nucleus which is rattier small. I
shall return to a consideration of these cells wlien I aescribe
the blood corpuscles of the Actinot ro cha.

As th.e blastopore lips bei_:in to close up posterio rly ( Fij^s.
lS(d)-(e) ), the endoderm cells in that re^^ion be^^in to lose
the power o^ .jivir^: rise to mesoderm cells but they are still
■^ound arisint; in a more anterior ret^iovi.

At a little later stage in which the blastopore has become
circular again after tr.e f\jsion of the blastopore lips and the

(25)

enteroii has almost rf^achcd the posterior end, a fev; mesoderm
cells are seen linin^ ti:e ventral ectoderm in t::e [.osterior re-
gion. (Fig.i;0(d) ) These cells, nowever, do not have their
ori,Gin -^rom the wall o'' tue posterior part of the enteron nor
from the ventral ec to derm v/hicn Caldwell (5a) v.oula call the
"primitive streak". The cells formin,, the ventral ectoderm are
very re^riQarly arran^red into a lawyer one cell thick ana all the
nuclei 3,re in a resting state. The mesoderm cells have eitner
micrrated from the colls of itl;e lateral cord whicii are j. ro-

lontrations o"" ti'ie sac , formin^^ the linini, of t ne preoral lobe
(■^ig,cO(e) ) or from the rej^ion of the blastopore vi'nero some mes-
oderm cells are still arisinfT. In ^^eneral, my int-'rp retation
of the facts bearinj^ on the orit-;in of tne mesoderm in tj.e post-
erior region of the larva agrees v,lth that of long champs (12)
for Phoronis Kov/alevskii .

When the larva reaches the stage sho'.vn in "'''ig.21 where the
blastopore is transverse and the archenteron -f^uses with tne post-
erior ectoderm, ti;e mesoaerm cells are found to be no re numer-
ous in the posterior re.;ion ijrid in nearly all cases, they are
applied to th.e ventral surface o -^ the blastocoel. Ac tnis time
the proliferation o -^ mesoderm c ells from the endoderm has ceased
in the anterior region arid there is no indication o"!^ any meso-
derm cells being given off from most a -<' the posterior region.

(k6)

At the extreme posterior enci of the eiiteron, however, a trana-
verse aection across ti:e larva ( t^'ig. ii2(d) ) shows a mass of
cells which mig-ht be taken for proliferating mesoderm cells.
Traced farther back, this mass of cells is found to be part of
the wall of the "posterior pit" or as Ikeda (9) has called it
"the nephridial pit". C^igs. iiii(e) - ( f )- (g) ) I siiall speak of
the fate of the cells of the nephridial pit in the description
of the larva with two tentacles.

Larvae like the one just described do not show thie least
trace o -^ a mesentery between the collar and trunk. In fact,
one could hardly say tiiat a trunk existed at this time. The
oblique strongly ciliated tract of ectoderm v/hich indica'oes the
line of origin of the larval tentacles has not appeared.
T^jrther Growth of the Young Larva.

The flexure of the preoral lobe continues as the larva
grows older. (Fig. 24) In this way a vestibule is fb rmed and
the original blastopore becomes the' part which connects the ves-
tibule and archenteron. (Fig. £4) This relation between the
vestibule and blastopore has been recognised by Masterman (16),
Roule (20), Ikeda (9) aiid Longchamps (12). Longchamps speaks
of it as a "stomodaeum" and MastenTiari ao ea also but the latter
adds "oesophagus" after it. (If my idea that a stomodaeujri
is a pitting in of the ectoderm wliich finally breaks through

(27)

into the enteric cavity ia correct, then Maste riiian* s and Lorii^-
charaps's use of ti^-s word is incorrect.)

Masterman speaks of a "sli^^ht ridi^e" runnin.-; around tne
edge of the preoral iaood ana tiien "do'.vnvvards till it is lost
on the surface of tr.e tentacles". Such a rid^e is not pres-
ent in th.e larva of Phoronis arcnitecta and there is no con-
nection between the ciliatea tract alon^ the line o-^ v/hicl-: tl^e
larval tentacles arise and ti:c ciliated ed^^e of the preoral
nood.

At this stare ('Pi.;i.24) a definite intestinal canal is seen
'Which, however, does not open yet to the exterior. The in-
testine, as described above, is not of ectoderriial origin in the
larva o •'^ Phoronis architecta. There is no pro ctodaouin. On
this point, my observations agree v.-ith tiiose of ''Jaste rnran, Long-
champs aiid Ike da.

Roule (20) says: "Un anus et rcct^mx se fa^onnent, aux de-
pens de I'ectoderm, sur I'extremite poste'rieure du corps."
(Page 102) aiid Caldv/ell (3a) derives ti.e intestine from the
remaiTis of the "primitive streak".

As yet the anal papilla is not at all definite but the
ciliated band blon,^ which tne larval tentacles are to arise
has now appeared. This is indicated in the sagittal section
( "Pig. 24) by a thio;kenin;_, of tne ectoderm.

{28)

The mesoderm cells v;hici- in "^it,. -1 are seen applied to
tlie veiitral ectoderm of ti: o larva tiavc iiO .; increased consider-
ably in number ana have become arraiiijea at quite definite in-
tervals. i'Fir.'^A) If tiie ventral surface o ^" trie larva is ex-
ajrdned, whilo the larva is alive, it will bo seen t^at the^o
cells have become simple muscle cells made up o f two rather del-
icate fibers whic-; extend from a large nucleus situatea near
the mid-ventral line. These fibers run parallel to one aiioth-
er around the wall of the larva. (Fig. 25)

The whole body cavity back of the mesentery between the
cavities of the collar and lobe represents the larval collar
cavity of the A.ctinot ro cha and althou£;h its somatic walls are
not lined by a perfectly continuous mesodermal epitr.elium yet
there are indications that such a lining;; is bein^ formed. The
ventral and lateral v/alls o "f* tne stomach, however, are perfectly
free from any epithelial covering. In fact, in all the Ac-
tinotrochae that I have exairancd, I nave uot been able tc find
a mesodermal epithelium covering the ventral and lateral walls
o-f the stomach in the collar region. I have never see-,: any
sign o:^' mesodermal sac -like formation sucii as occurs in the
preoral lobe.

Roule (20 page 11£) iias described in a conside --ably older
larva th.an the one v.-itn ;viiich we are dealing certain mesodermal

(29)

cells to 'rfiich he has c^vcn the iiaTric "conjunetivo-niusculaires
elements". These ne represeiits as spii.dlo-shapecl cells terrrd-
natec by lent, fiber-like pre loiitjations ana he has n^ured them
as beinr quite numerous in the "plasma, transparent et consist-
ant", of the coelorrdc cavity. While the youu;. larva of Pno-
ronis architecta bears a close reseiublance to tnat o-^^Phoronis
Sabatieri described by Roule (liO) , yet at no time durin^ the
life of the larva have 1 seen these cells suspended in the
body cavity in ducx. numbers as he has shovai, Gpindle-shaped
cells with lonr pro Ionizations are quite numerous but t'.ey are
usually found applied to the somatic walls of ti:e larva.

Although recent investit^ato rs have throv/n some doubt on
the existence of tne lobe-collar septum yet 1 am satisfied that
such a septum exists in the larva of Phoronis arcnitecta.
Ikeda (9) has shov/n that it is incomplete iv. the old Actino-
trocha ana my observations aji;ree witx: his but it is a fact,
nevertheless, that the septum is continually present throu^^hout
the larval life of Phorcnis arcnitecta ana that it makes its
aqipearance at a very early sta^e in tx:e li-^e history,

Lon^jchamps (12) says "Si une subdivisions plus ou mo ins
complete s* etablissai t , entre ces deux regions, elle ne seriat
en tout cas que secondaire, et la cloison s'edifierait aux de-
pends de mesenchyme". '''"'rom what I have sai a above,- it is

(30)

plain that I caimot agree with Lont^charrips in hiy statement that
the septum is secondary. It must be adndtlsd, however, tiiat
the septinii between ti;e lobe and the collar is o-f'ten consider-
ably thinner thaii that between the collar auu tne trunk. if
1 h.ad net follov;ea its ori.-,in from the earliest stages by means
0^ sections in three different, planes, whole ri'ounts aiiCi live ma-
terial, I sliOuld not have been inclined to consider it, as I dOj
a primary and constant o •"^an o^ the larva.

I had confidently expectea to find in the larva of the
sta<?e represented in ^ig. 24 some indication of tne mesentery
between the collar and the trunk, but I was disappointed, Al—
thougli the ciliated tract alon(, Yrtiich the tentacles are to
arise has made its appearance ana extends obliquely around the
body poDper of the larva, inaic at in^- a line just a little above
tne line o^ separation of the cavities of the trunk ana collar
in the older Actino tro cha^yet exaMnat ioii of sectioxiS does not
show the least si^^n o '^ tiie mese^^tery or its funaament.

Ikeda (9) has found mesoderm cells connectinj^ ti.e nephrid-
ial canals with the splanchnic walls arid i.e thinks tney are
the first inaication of the septum between the collar ana
trunk cavities. I have not been able to find th.e pairea mas-
ses of "hypoblast cells" which Masteman( 16) says give rise to
the trunk cavities although it is true that I fbund mesoderm

(31)
cells lyin. on the cio rsal wall of the intestine. Masteman
does not follov; the fate of these masses but in tt:e larva v/ith
three pairs of tentacles he s^-eaks of "the two mesocoels push-
ing aorsally their walls fc rrainj, a pair of conspicuous ruesen-
teries witn the wallc: of the siatacoeles" . (pa-.e o9o)

As I hiave said before I have not found the masses o"^ cells
that I.'iastenrian (16) speaks of but I do not aeviy that tne condi-
tion v/hich he describes may not exist in t ho larva of Phoronis
Euskii y.'ith three pairs o "^" tentacles,

"Ilephriciial _P i.t_^._ ( I xe d a )

A structure of the larva of Phoronis which has t;iven rise
to ccnsiaerable controversy is ti;o "nephridial pit" ("posterior,
anal, ectoblastic pi t" , "posterior aivert iculum" ) . It seems
safe to assume that such a stn;,c turo oxists in the youn^; larvae
0^ all species of Phoronis, It has bc^n seen by Caldwell (Zci)
in P. Kov.al'JvsKii , by Ikeda ^9,^ in ?. Ijimai, by Lon^chairips
(1?) in P. Kowalevskii, by Mastenrian (16a) in P. Euskii and
P. hippocrepia and by myself iu P. architecta, Althpui^ii
Hjule (£0) has not observed tne pit in P. Sabatieri, it seems
probable, tnat sucli a stri-ctrire will be fbuna tiiere on further
investie;ation. I can.no t believe tnat Roule's understanding
0-^ tj-e o^J(/in uf tn; nc:..hriciia from two cell masses of somat-
opleure synunetr-ically placed at the sides of the larva

(32)

is ccr'-ect. As ytatca abov3, I consiuer tne pit to be of ec-
todennal origiu. (Fij:.24) Further stuay of the stn.ct'jre
leads me to agree with Ikeda that it divides into two lateral
branches each of which becomes a nephridial cai.al o^ the Ac-
tinotrocha. (Fit^a. 26-27-26-2.)) In Fig. 25, v;hich is a draw-
ing made from a living larva, the canals whicii in a little
younger stage were practically tr.e same aiameter throu^^hout
their length have becoruC tippea at tn ei r aistal ends wi tli a
bunch 0-^ cells v/hich, I believe, are later to form the excre-
tory cells of the nephridium.

I am unable to maKe aiiy positive statement concerning the
origin of tiiese cells, since it is difficult to obtain many
larvae o "^' P. architecta which are old ciiough to show ti.ose
bunches of cells in ti^e process of formation. From all the
sections that 1 have examined I have not had any evidence that
they are fonriod by free mesoaerm cells attaching-, tijomselves
to tne internal ends of t ne nephridial canals ana I am rather
inclined to consider them as arising from the cells of the
internal blina ends of tne nephridial canals. (Figs. 25-28)
Ikeda's description (9) o f the way the nephridial tubes arise
from the cctodem^al pit; i. e. by tr.e "recvagination of the
distal luipal'-v^u ^.crti^n of the nephridial pit%b-ee.Tfc> 'lo me to
be correct. Lon^champs* ( 12) interpretation of ti;e chaiige in

(35)

form of the "ectoaermal pit" a^^rees q^uto clooely -.vitii Ikeaa's

descrii tion,

_ "Medullary Plate", J Ro u le )

When the youii;,^ larva of Pnoronis a^chitecta nas reaciied
the tvv'o tentacle stae,e, cro^y sectiono csiio-: ti.at 'Ci.ere io a aef-
inite ve..tral ciliatea bam extenaiUf^ from the moutti to the cil-
iatea tentacular band. ("Pigs . 29 ( b) - (c ) - (a) - ( e) ) Tiii^^ ven-
tral ciliatea bana has been observed by Roule (20) in the larva
of P. Sabs.tieri but it has not been aescrihed for any other spe-
cies. Roule has hcmolot;izea it with the i;ieaullai"y plate or
medullary i^roove of the annoliu larva,

Lon;,:c]-;amps has drav/n attention to a -^i^^ure of an Actino-

trcchia published in Hatschek's "Lehrbuch ae r ZoolOi.ie". In

this fit^;u.re are represented two coelomic sacs surroundinf: the

intestine, Katschck docs not dose: be the orij^in of these su.cs

but Lon^champs (pa^-e 555) proposes the question, "si les canaux

a
ne deriy^ient pas des expansions lat o'^-i.j.:^ av dive-^ticulc ccto-

blastique, chacun dcs canaux restant en rapport avec I'exteV-

ieur par un orifice re'sultant du dedoubloment ae l»orifice ^Hm-

itif et median, tandis que le restant au aiverticule ectcblas-

tique deviendrait la cavite posteVieure du corps,"

Suchaii origin for this posterior cavity would seeiL to be

a possible one and^woula t.;ive an easy explanation for the ori.in

(34)
0^^ the colly,'"-t nuik and ventral .ixea enterics.

IL ia KiV opinion tiiat the cavity of the trunk id for'neo in
the followin*: inanner. As the tentacles i^row out and increase
in number, the posterior rej^oi. of the larva about ti^e rectum
increases greatly in length. lii aoing the latter, the luesoder-
mel linin;: of the collar is dravvn away from the somatic wall in
the region back of the tentacular banc, •■na a cavity in left con-
taining the rectum, part of tj:e stomach and ttie proximal part of
thie nephridial diverticula. At tne sane time this is takiii^,
place , certain cells, v/hich I believe have their origin from tiie
base of the nephridial diverticula, give rise to the lining of
th.e cavity o "^ t-^e truiik. As to the manner o ■•" origin of tiiese
cells I am still ixi aoubt. 1 have not been aole to fina tv.'O
coelomic sacs wj;ici. Hatschek (6) seeius to have fLj-iUrea (It is
possible that nis figure is meant to represent a sinj-;le sac cut
at two places) aiia I have nun tea for them in larvae vri.ero the
diverticula are Just beginnin.. to form ana also in larvae v:i tli
t'.TO , four and six tentacles. In one specimen -.vith tv.'o tentacles
hov/ever, ("F'ig.SO) I iiavc founa an arrangement of meaoaermal
cells on the dorsal side of the intestine whicn seems to be the
beginning of a sac; this, however, is net paired. V/hetiier this

sac and its cavity give rise to tne lining and cavity of t.;e

or not,
trunk 1 caiuiot sa:^ for 1 have founa but one specimen in v/nich

(35)

this condition exists.

One thiiit^ is certain; tne fully oevelopea trunk cavity of
the Actinot ro c>.a has a distinct inesoaernial linin,, consisting
0-^ a somatic and a splaner.nic layer , As far as 1 knov: all
Actinotrochae have a ventral raeaentery which, fact tends to-
ward tt:e view that the lining, of the cavity of tne trunK has
its origin i^ri a sac which grows around the rectum and posterior
part of the stomach. Wlr;ether the fact thiat there is an indi-
cation of a dorsal meseiitery in the pobterior re;_;ion of some
of the fully developed Actiiict rochae, Species, B, , has any bear-
ing on the double origin of the cavity of the trunk or not,
I cannot say '"or I have never seen the very youn^;^ larvae of
this form.

The youngest larva taken from the tow haa thiree pairs of
tentacles with beginnings of tne fourti; pair. In this larva
the tentacles naa grown considerably in length and ti.e posterior
region had become somewhat elone.ated. (Fig, 31) Only one spec-
imen of this age was obtained and I was only able to study it
alive. The rresentery between the collar aid lobe v/as plainly
seen and there seemed to be a ti:in mesentery between the re.;ion
of the collar aad tr.e younger trunk re^^ion. The nephriaial
canals were seen with difficulty but the rounded bunches of
excretory cells forming tne internal ei.asof zne canals were

(36)

plainly vi sibl e.

7/hen tl:e larva of Phoronio arcnitecta has five paird q-^' ten-
tacles {'^ic,22) the trunk rej^ion is elonL,ateci considerably ana
constitutes about one half the leni:th of the larva. In fact,
the. larva at tn i,s stage looks much like th.e -^lly aevs-lopea
Actinotrocha, The "retractors" described by Ikeda (9) are noT.7
present and the body wall in the anal rei-;ion shows a Uiickeninj
which is to become ti^e perianal ciliated band. Thd a larva shows
clearly tne presei^ce o ^ t vro ii^senteries.

In the larva v;i th six pairs of teijtacles (Fig.3o) all of
the orgar^s of the fully developea Actinotrocha are present.
The ventraj pouch bCj^ins to invaginate ("Pig.Si^) and sections
usually snow tia,t tlie blood corpuscle masses are formi-ng,
"i^ully Developed Actinotrocha.

There are two species of Act inot ro chae found in the v/aters
of Eeaufort harbor aifid they a,re very similar if not identical
with the two species tnat E. E. V/ilson (24) observed in Chesa-
peake Bay. From the latter part of May until tne latter part
0+' SepteiTiber both species are fairly abundant in Ui.e tow.

V/ilson has aesignated the t v/o species found in Chesapeake
Bay as Species, A., arid Species, B, , and because of the general
agreement betv/een my observations and his descriptions I shall
speak of ti:e Eeaufort ^c ti no t ro chae as Species, A. and E.

(S7)

althoiu-h I am satisfiea that Si.ecies, A., is t ne larva o"'' P.
archi tecta.

Species . A. :-

Species, A., (Fig. 34) is soraewhat smaller than Spec i es , E. ,
aiici its averat;e leriti'ti. is l.Oo miri. Tne trunk is quite stout,
thP intestine is short ana the posterior end of the stoiiiach
reaches as far as two-thirds of the lenrth of ti.e trunk cavity»
vVhen about ready to metamorphose, this larva usually has It lar-
val tevitacles and an equal number of youn;_^ adult tentacles. The
adult tentacles do not usually appear until the larva has It
larval tentacles (its full nu{tiber) arid they arise as thickenings
on the under side of the bases of the larval tentacles. In this
respect the larva resembles one of the Actino tro ciiae v.hich Ikeda
(9) has described. The blood corpuscles are found in tVk'o mas-
ses usually applied to the ventro-lateral surface of the stom-
ach ai~.d they make their appearance in the larva with Ik o r 14
tentacles. A pair of irruscles which Ikeda has been the first
to describe and which he has called "retractor muscles" are al-
ways present. T have not been able to make these out in young-
er larvae than those with ten tentacles. This species is wi Ui-
out the so-called "stomacii divert iculae". Pigment cells are
found rather irregularly scattered on ine wall of the body cavit.
There are definit6 aggregations o^ tnese at the bases of the ten-

(36)

tacles and a fev; pigment cells are seen on the surface o ^^ the
blood corpuscle masses. Usually there are quite a number in
tl;e wall o^ the posterior portion of th.e trunk.

This Actinotrocha is not as active as Species ,B.,atici it aoes
not, as a rule, turri up its preoral hoed vmen irritated. Its
iiietamorphosis usually takes place quickly, in or 20 minutes be-
in^ required f^o r its completion. Actinotrc ciia Species, A., I feel
certain, is the Actinotrocha of P. architecta.
Species, B. (T^if:,.35) ;-

This Actinotrocha is larger tnan Species, A., and v/hen
about ready to inetamorphoso, it ,;as an average length of 1.22 nra
and las at least 2G tentacles. (v/il3on(24) figures tne Actino-
trocha Species, E., ready to inetaro rphose, vvitn 22 tentacles.)
The difference in appearance bef^een this larva and Species, A.,
is rather striking. Eesiac being some;7hat lon.^er, it is slight-
ly narrower in the collar region ana aeciaedly so in the trunk
region .hich ,,ives it a rrruch more graceful appearance than that
0- Species, A. Tne intestine is ,uite lon^ extendin, through-
out the posterior t;vo-thirds o f the t nuik cavity.

M. Longchamps has kinaly pointed out to me tnat the "adult
tentacles appear bilaterally, the mia-vontral line bein,., at
first, free of the buds". They do not arise, however, as tnack-
enings on the under .i,e of the bases o- the larval tentacles as

(59)
in Species, A. They r.ave their origin at tl;e base of tue lar-
val tentacles but they are separate from them ar^ tney appear
first in the larva with 2A tentacles.

This Actinotrocha ai ffers in three important respects from
Actinotrocha Species, A. In the -first place it i:as its blooa
corpuscles aggregated into four masses, tvio of v;hicu are usually
in the sar/iC position as the pair in the smaller species. The
other two, however, are fouvia, as a rule, more aiiteriorly in
the collar cavity ana are api-lisl to the oiorso -lat eral walls
of the stomach. The posterior pair lying on the vent ro-later-
al sides of tiie stomach make their appearance iuriiig the 16 or
kO tentacle stage but the other pair do not appear until about
Lhe 22 tentacle stage.

This larva also has retractors exteviding from the ganglion
to the region of the first and second pair oT tentacles.

A second point of difference is the fact that Actinotrocha
Species, E., possesses a pair o ^^ aiverticulae at the aiitorior
end of the stomach. These T founa to be present as early as
the 22 tentacle sta-.o.

This larva cari further be aistinguishea from t'.e other spe-
cies by the fact that there is tbund in the older larvaea seii-
30 ry papilla on the irda-aorsal surface of the preoral lobe.

Actinotrocha Species, E., is much more active v.hen irritatea

(40)
thati the other species. Tr.e least ix-ritatiou causes it to turn
up its hood ana to assume attitudes like those fii;urod by Master-
nm-i (15). In fact, judrin^ by the flcures and text of Master-
rr^an's pape^, it seems that there is considerable similarity be-
tween this larva and the one he has described. The two larvae
are very much alike in shape and bo tii have tlie late'-al stomach
diverticulae but t).e form that Maatennari describes has only t'.vo
masses o !^ blood co r^jus cles , The two species are not identical
nor is Actinotrocha Species, E. , identical 7,'i tii Actinotro ci-.a
branchiata from t l:e liorth Sea for, as Lonijchamps has pointed out
to -Tie, the latter has but two blood corpuscle masses, Lon-.cr. amps
has informed me that in Actinotrocha Species, E. , the adult ten-
tacles make their appearance in the same special v/ay that they
do in Actinotrocha branchiata (^ound near Helcpland aiid de-
scribed by J. Jlvlle c (19) ) and Masterman {16) says in liis pa-
per that the form he workea oa "does not appear to differ in any
essential re"spect" from Actinotrocha branchiata. There seems,
i;cv/ever, to be considerable difference in size between Actino-
trocha braiiChiata and Actinotro cna Species, E, , for, accorciin^^
to Loncchajdips, the best developed specimen tiiat he obtained of
this species measured 2 mm while ti:e length o^ Actinotrocha Spe-
cies, B,, averages 1.^2 urn.

Although Actinotro cha Species, A., seems to metamorphose

(41)

without any difftculty v/hen brought into tiie laboratory yet I
have never been able to inauce Actinotroctia Species, B. , to do
so. I have kept specimens for ten day a or luo re (the pouc>i and
blooa corpuscles bein.:; v/ell develcpea) and in some cases they
succeeded in evaginatih;-; the ventral pouch but ti.cy were iiever
able to complete th.e metaiTiorphosis,

As far as I know the aarlt of this Actinotrocha has never
.en ^ound but I think it probable that it lives under quite dif-
ferent conditions frora PhcTDnis architecta and 1 should not be
surprised i f it were found to be a deep-water form.

Tnternal Organization of >_he_ "Pully Developed Acting troci.a.

"Subneural Gland";- (Masteraan) Masterinan (lo) has de-
scribed a depression in the dorsal wall of the buccal cavity
vdiich he terrts a "snbnoural Qld.XiO." and which he compares v/i th
the glariO of tne same name in the Tunicata and also possibly
••-i ti-. the hypophysis of the Vert eb rat a.

Roule (^0) and Ikeda (9) are of the opinion that this de-
pression is a pf'oduct of the fixin^ method.

Lohi^champs (12) does not consider it to be an accidental
structure but lie does not aj^ree witn Masteniian's view as to its
tiieoreti cal si ,,ni ficaix e.

I'^enon (17) says that the "subneural £-,land" nrst appear o in
connection with the collar ana that durinj development, it shi-^ts

(42)

forwara iixto tt-.o i.reoral lobe but in aiiOti'.er part of hi a paper
lie says, tlie ogsophat:v,s is ofteii foldea transvc r-aely (this also
the case in the yoi.iii^ Phorciiis) iixto pouciies and the "subJ-ieural
.land" is a diverticulum of its dorsal v.all,

V/hile in examining, sections 1 nave ■f're quently foirnu a ae-
pression in the re^^ion tiiat Masterruan (15) indicates, 1 have
never -f'ound it in the livin--, larva, ■ Only in verj poorly killea
larva,e have I found the depression to be as deep as LiastenTan
i.as siiom. ai'id in all cases the structure of the vrall is practi-
cally liK'e that of the oesophat-uis,

I'n the Actinotro chae Species, A, ana E. , there is no de-
pression in the livin:_, larva -.vnicii mit;;ht be homolOj:ji zea to the
subneural ^land of hi^^her animals and I am forced to aj^ree with

Roule and Ikeda iu tiieir belief that the so-called "subneural
t.land" v.-hich Masterman describes ia a product of fixation.

"Oral aiid Atrial urooves":- (Masterman) Masterman (15)
has observed a mid-ventral ciliatea area leading, into tlie mouth
■^rom the preoral lobe in front and a broad ciliatea area ae-
pressed into two oral grooves leadinfc, into it f'-om the ventral
surface of the collca.'- c^n.o,. Ho has also seen two oo-called
"atrial grooves" leadin^^ into the do rso-lateral corners o f t he
mout):. Masterman says ho does not find gill-slits in ^Ir. Ac-
tinotro ci:a nor does he find structures tnat he considers to be

(45)
their homolo£;ues. "The atrial j^roovea" o i' t i.e Ac finotrccha,
he saya, no..?v-.-, are the r.nalOt^tics u^ ^.i! 1-slito. (15-page 319)
On par.e o5C (15), however, ho says tiiat "tentatively, 1 v/ould
regard the atrial grooves of the Actinotroci:a as t);e early rudi-
ments of phar:/ngeal clefts as found in Cephaloaiscus" .

His "oral grooves", he says, corresj^ond with t lie oral
grooves in CephalodisciJ s.

Resile (20) aoes not fina tne "atrial grooves" but finds
t'.vo lateral grooves which he considers to be fonried by the in-
sertion of the hood Oil to tno collbir wall.

Ikeda (9) ana Lcn^champs (12) are of ti:a opixiioii th^at these
grooves do not norx:ially exist,

I have L'laac a careful stuay of tr.o live Ac tine t •"ociia and
of surface moiuits but have .^ot Loen able to make out tneae
grooves in either Species, A., or Species, B. Sections, how-

over, siiow that the "oral grooves" are present aijd that in most
i- reparations v;here tie preoral hood has been turned upward by

violent contraction (due to tne fixin_ agent) theru are two

in
snort grooves in the po sition, which Masteraaji +'inds the "atrial

grooves". ju tnose cases in which the hcca rerriains in its no r-

r.ial position I havo seldom fuuna Masterman's so-called "atrial

grooves" uiid even in a fev; cases where tne hooa is tu-ned upwara

they have been absent.

(44)
Tlie ventral v;ali of the hood just as i t t-asaes ivito the
wall of the oaaophai>is not infrequently siiov/s a pair of bilat--
erally situated grooves which are similar to those tD una on the
ventral collar v/all,

"Ilouropore" ;- (Mast .-iiian) Sjj section on the nervous sys-
t eia,

"Subneural Sinus":- ( Mas t 3 rrnan ) Anc t hv. ?- <j rgaii v;h i c h Mas -
tennan (15) has dv^scrib^^u is a sinus irfunoaiat ely belov/ the ner-vG
t^anj^lion causea by the v/ant of coxitigiii -.„ c " vaeii tne xnesoblas-
tic walls of the preoral cavity and the collar cavity. This
sinus, he claims, is closed except for a fissure which leads
eventually into the dorsal blood vessel. He compares this si-
nus to the heart of Balanoj^lossus.

Mcnon (19), as far as I kiiow, is the only other worker on
the Actinotrocha who claims that there is a aefinite vesicle
beneath the gan^-lion and he has discovered no connection be-
tween its cavity am the dorsal blooa vessel,

Roule, Lontjchairips and Ikeda do not find tt-. is on^an, but
the latter recognizes tne existence of 5 space ("posterior re-
cess") free from mesenchymatous fibers which is the posterior
part 0"!" the preoral lobe. This, however, he says, aces no t
connect with the aorsal blooD vessel,

Prom the st?.'ay cf the. early development of Phorcnis archi-

(45)
tecta and the orii:in O"^' the iTiasGnter/ betvvenu the hood aiia the
collar, I have come to tho conclusion th.at no vescicle is forraed
in tnat species between the two la.yers of the inesentery (i"f two
layers exist). The ineseia ery which forms tiie posterior wall
of the preoral lobe cavity is found attache a just back of the
gan{:lion in the mediaji line aiid there is not ti.e least sit;n of
a vescicle other than tiie cavity of tne preoral lobe. ('^it;.24)

In neiti.er Actinotrocha Gpecies, A., nor Actinotrocha Spe-
cies, B. , have I -^ouna a vescicle below tlae gan^.l^on althoUi_^n
in both, cases there is a space such as Ikeda (9) has seen, ^ree
from mesenchymatous fibers. The anterior boundary o +' this
space is rather sharply defined and occasioiially amoni,. loii^-i-
tudinal sections a fiber witi; a nucleus is seen runnincj verti-
cally from the dorsal to the ventral wall of the hood, .giving
the appearaiice of ari aiiterior v/all to the space. These fibers,
however, are very much more uelicate than the wall of the collar-
lobe septum and v/h at is more, they occur Oi.ly occasionally and
are evidently not sections thrcUi_,h a membrane.

In the Actino tro chae, which I nave examined, there does not
exist any vesicle beneath tno nerve t;;a:ii'lion nor any structure
which 1 could liken to the heart vesicle of Balanoi^io ssua.

l^'or the supposed relation of the aorsal blooa vessel to the
"subneural sinus":, see Hlood System.

(46)

"Stomacii Divert! culae" ;- (Ikeaa, Loiii_^cliamps aufi Menon)

"lio tochorajs" : - (Mastermau and RoiJlf')

River since Jonaimos Muller (19) saw the i,c:irfia "bliiildarme"
iii /^ctiiiOtrocha brarichiata. nearly all o^ tliose vvno have atuaiea
Ac tinotroc-jiaehave observed the same structures. Some have con-
si deroa them to be liver diverticulae , others i-^ve described
tnem as dark masses with ;jlobules and as brown specks. Wilson
calls them ".^^and-jxar lobes of the stomach".

lkecia(9), Lon^champs (12) and Kenon (17) speak of them as
"stomacn a1 vr'-'^i c"? lae" but they ao not ascribe any function to
them.

llasterman (15) and Roule (J:!0) look upon them as riidimontary
;xOtoci:orcls.

Roule, Ikeda and Lonrcharops have studied larvae in v/hi ch
the aiverticulum was not pairea ana lateral but unpai rea ana me-
dio-ventral. The latter inves tij^ato r has observea larvae of
both types,

1 find that in Species, A., tno diverticulum is undevelot-Cd
^ven at the time of metajnorphcsis while in Species, B. , *i:'' ai-
verticulum is pciJ i-ea, well developea and vent ro-lateral,

Loni:,champ3, it seems to me, has very justly ub joe tea to
Yasterma.n's use of the name "Diplochorda" under which tteie latter
incluaes tne Fho^onidae ana Cephalodiscu s.

(47)

The diverticula of Species, E. , uo not sijov/ ttic rej.iilarly
arr-an£;ea vacuoles ■.vhicii Maat errrjaii i-.as aeacribea for ti.c Actino-
t roc ha from St. Aaiarews Eay. In fact, 1 aj/ree with Loui^caamps • s
(1^.) observations in fiiidint: the histological characters abso-
Inr.r.iy aifferent in Species, A. ana B. , from the hiatoloijy of
notochordo ano there ig not t!.c least inaication o '^' supi-ortin:^
tissue. Hov/ever, larvae whicii I have examined fixed in Flem-
mint;,*s fluid have not snov.Ti ti:e vacuoles to be filled -with fat
droplets as Longchamps states.

Sections throu^jh the aiverticula o-^ quite ola larvae ("^it;.
55) stained with iron haematoxylin sho v/ columnar cells, nearly
every one o-^wl;ich contains a deeply staiiiin^^ body about one
quarter the size o+" the nucleus. The bodies are liO t found in
the wall of the stomach proper ai^a I believe that they t;ivc the
yellov/isi. brov.ii color to the diverticula of ti.e live Act ii^ot rocha

Iri some cases I have founa clu larvae in v.iiich L -.e cells of
trie oiverticula were vacuolated taut in these cases I have also
found that tJ.e eiitire stomach wall was vacuolated. Tne vacuoleij
were nev^'r large enout^h or liumerous Oijout^i; to alter ti»e natural
position of tne nuclei.

Accc-ain}^ to kasterman's dascription, the first vacuoles
are formed at the distal ends of the cells ana more vacuoles
arise lat-r bctweDn these ana the inner ends of the colls.

(48)
As far as I knov/, tno crij.;,iii o ■:"■ vacuo lateu tissue in verte-
brates is the reverse of this, tne vacuo liiiatioii be._,iruiiiii, at
the c elite'" of the co ra avici travelliu-:, outwara.

The srecimeiis o f Actino trochae o +" Phoroiiio Sabatieri which
1 have examined sraw the stnjcturc of the stoiiiacn diverticulum
to he very similar to thjat of the diverticulum in ii;o Actino-
trocha Sfecies, B, The diverticulum, hov;Gver, is somev/hat
more vacuolated in the former ti.an in the latter but it uoes
iiot s^.ov; the peculiar structure which Mastermaii has describea
■'or the "no to cho rd" of the species from St. Aiidrews Bay,

I fail to see wiiat use li.e Actinctrocha has for any o ri_,ai;
of support in the ro*:^ion •>,tii:ire the aivcrticula arf found am
it seeriis much more probable tu mo that they have a i^landular
fuiiCtion.

i;5'-Vu'..';s System;- It id {.generally aamittcu, I tiiinK, cik-Uii^
investitiators who have stuaied the anatomy of the Actino t-^cha
carftfu'lly teat the creature lias a su.bepiaernal layer of iiervcus
tissue , ti:rou,,hout tue body v.iiich is fibrillar in character.

This nervous tissue assumes the form of quite definite^
tracts in certain parts o "^^ tiie body in Actinotrocha Specieo,E.,
uju fairly v/ell developed nerves can be said to exi.yt, Tne
mo3t conspicuous ones are +-ound in the median dorsal line of
the p-'-^crjil hood-as ti.ree aistinct longitudinal Lunalos of

(49)

nerve fibers •'xteiiclini.;, from the gaugliou to t no ant ?'-'_'" cut^p"
of ti;e nooa. Trie re are other tracts, wnich thouj-^h they are not
as definitely marked out as ti:e above, are uacioubtealy nerves.

Masterifian (15) in nis ..crk gij the anatomy of the Actinotrocha
•Tom St. Aaidrews Bay has det-cribed a complicated nervous system
kvt tl:e investi t^ations of Houle (20), Ikeda (9) aiia Lon/^champs
(12) navo tr;nD\',ii considerable doubt on tne correctness of his
observations. Whether these aifferences have been aue to dif-
ferences in the Actinotro cr;ae st'^aied by these workers or v.rietn-

are
or tney^ ru'e to the technique it is impossible for me to say,

but jud<,inr from the difference in the aCf/ree o •*' development tiiat
I have found between the nervous system in Species, A. ana Spe-
cies, B,, I aiii j.''^u to believe tnat the disagreements are due
partly to the fact that no tv/o oP these investigators have stu-
died the saraf: species o -^^ A.ctinc t^ocx-.a.

V/hile the nervous system of Species, A,, can v.'i tr. careful
study be shown to be very similar to that of Species, E, , yet
it is so feebly developed tr^t '.without first naving studiea Ac-
tinotrocha Species, B. , 1 should not have been able to see the
sirrdlarity in t.he disposition of the different nervous tracts.
The ganijlion witn its three aorsal lonj^l tudinal nerves runnin^j
alonj- the median line o ^' tne iioou is easily seen in the live
larva of Species,. A., but in sections I have found it impossible

(50)
to tracf; the latter. The sensory papilla mentiouea in the de-
scription of the Actinotrocha Species, E. , is absent in this
speci es.

I ata pleased to be able to confirm, to aoriie extent, llas-
terman's (15) description of the nervous system of the Actin-
otrocha, especially since a. snaaov; of doubt has been cast upon
his v^ork by some v.ho have studied the Actinotro cha.

P3,rtly because Species, E. , seems to be a much rr.o re hii:h-
ly developed Actinotrocha ti;an Species, A,, and partly because
of its similarity to the one tj;at Mastermaui studiea (v.i.ich is
of 30 m'.ich tiieoretical interest) 1 shall confine the descrip-
tion Bjtid figures to the nervous system o f Speci es , E. , al-
though I am convinces that this Actinotro cli a is ViO t that o '^ Phc-
ronis architecta but of an adult that has not beeii discovered.

I must admit ti.at I have bcon very unsuccassfi.il in the at-
tempt to study the nervous system of the Actinotrocha by means
of methylene blue ana aiimionium molybdate. Gola chloride jias
f.^i ven me no better results thati stainin^,, with iron haematoxylin.

If the dorsal surface of the hood of a live Actinotrocha
Species, B. , be examined one will fina that tr-.ere are a threat
many fibers which run in more or less definite tracts, (T^ig. 36)
Many of these fibers have nuclei alon(, their course and are un-
doubtedly muscl&v fibers v/hile others run to the ed^^e of the

(ol)
hood and there seem to be c ontir.uatioris o-f" certain cell-like
bodies which Ikeda v;as tne +lrst to describe, {'^ir,o7) Al-
though I have seen these bodies on all occayions in surface
vievs stained with methylene blue yet iii sections 1 have never
been able to niake then out, i ^^ they are nerve colls. It must
be mentioned, however, tl-.at in transverse sections throu.-;!. the
edge of the hood evet^y 2M section shows at least one nucleus
closely applied to the rin^: o -^ nervous tissue running, rouna tlie
ed(.:e of the hood. {'^i^.4Z) These occupy the sarie position
witii reference to the ediie of the hood tl-.at the coli-like bod-
ies do vdiich. are seeii in sui^faco views, but I take tiieiri to be
the nuclei o-^ muscle cells a.nd frequently I have traced deeply
stained muscle fibers arisin^^ from them. (T''i,_;.42) V/ithin
ti.e nervous tissue of the treoral rin^:; I have not been able to
^'ina s true turns whici. I coula consider to be tr;e cell-like
oodies menticneu by Ikeda (9).

Ikeda has fiijured a j^reat many fibers arising, f-xin tiie gan-
£:licn but in the Actinot »"ocj.ae that I have oxaiain-.^ 1 i. ve not
been able to s::'- ^f.^ conncc^^^ns, however, I ao not wi 6J. to
deny that they exist.

The three medi aii nerves arisint., from the aiiterio r side o -f^
th»e t'an^^lion and running -forward to the edge of the hood and
two lonri tudinrjj. tracts of nerve fibers arisin,r from the post-

(52)
erior aide of tiio jiangliori CcUi be easily made out but tine large
maJo*~it.y of fibers which compose the broad tract shov.n ii. "Pig. 56
are net connected v/ith the nerve gant'lioij. There are some inai-
vidual aifferences in the arrangement q-^' the above tracts but
in general tiiey are about as si-.o vm in Figure Z6.

On either side of the medio-aorsal line in the region of
the youngest tentacles a tract of fibers can be seen running^
loiigitudinally. In the re.jion w't.era the edge of the preoral
hood is insertea into the collar a small tract made up of a
few fibers braiiChes off ■•^rom the aorsal lont^itudiiial tract and
passes iiito the edge o "^ the preoral lobe. Somev;hat fartr.er for-
-NS^r^l eacli aorsal longitudinal trjnK .^^.r^^aa out sometimes into
tnree rather indefinite tracts most o^ whose fibers seem to
reaci thj oug^ uf tee hooa. llaiiy of thc^ fibers o"^' tnc antj:^.^cr
bravicli appear to end in the region at the siaes of th" ganglion
but 1 could not my-ke cut arg/ connection v/ith t;.j latter,

Iminediately posterior to the ganglion a tract of fibers
(Fig. 56) is seen which runs ^c r a short distanc:. transversely to
the long axis of the Actinotro cl.y. On bo tii sides the fibers
0 -^ this tract soon diverge from one another and in t:.is v/ay,
distribute theniselves over the anterior part o *' ti.e l;ood, ending
at the edge of the latter. (Fig. 56)

Maste'-ma.n (15) naa figured (Plate xviij , "^i,.. 2) certain

(53)

nervo tracts oii eitirier siae o"*^' the three uerves arj siii^ froni the
axiterior end of the i^a.'i.ir,lion am fiiicis that the.se "run forwards
ana outwards aiio' then bend bacicv;ara£r and take a courde to the post-
erjor corner o-^ the nood."

A lateral view o:^ tne hood of Ac tino troctia Specieo, E. ,
b!ov/s sometimes -^ibers t^atnored to^^etner in trunks but these
XiQV3r take the direction as shown by Masterman. They diverj^-s
rather regularly aiid end all alon^^ tne eajj;e of tne i.ooa ivisteaa
of at the posterior corners of the sa/iie, (Fit,. 37) Tiiey are in
no v.'ay associated with the gaiitlioi^^ ai'i^ cto not iiave the etpfear-
arjce of being even when tiie hood is turued upward out of its
usual position.

"For several reasons, I believe that the coiriplicatea tracts

of fibers seen in a su'^face view of a live Actinotrocha Species,

B. , are not iierve fibers but muscle fibers. "Pirst, maiiy of

celxs.
ti-.em show alon> tneir course nuclei resejublin,^ nuclei of rriUscle,

Second, cross sections tiirou.^1: tne hood show tuat there is a
rather heavy lining/ o-^ muscle fibers v/iiich run in the same j^en-
eral direction as ao the fibers shov/n in the surface viev;. Third,
tnere is no coiniection between these fibers ana tr.e iierve gan-
glion.

T^Vom ti-.e posterior side of the ganglioxi tv/o tracts of nerve
fibers pass out BXid can be traced backward some little distance

(54)
but they are soon lost to view as Ikeaa (9) has founa to be
the case when stuayin.; methylene blue preparations.

Sections tl:rou-_/i Actino tra cl;a "peci es , B. , brin^: out quite
plainly certain nervous tracts w'r.ich appear as thickeniiigs of
the subepidernial nervous tissue ana v/hicl-t correspond in a lar^^e
part to the principal nerves aescribed by Masteriian,

AiTterior to the ^ai-t^lion a section throu^^h the i^ooa siio ws
the {:arallel nerves wr.icn run from the anterior side of the gan-
.jlion to the anterior ede;e of tiie hood. The boundary of these
nerves as sh.own in "Pig, 44 is a little too definite. The sub-
epideriT.al nerve tissue which for/as a thin layer below tiie ecto- .
derm cells is iiO t shown in the series of sections to be de-
scribed.

■Pcllowin.^ the sections posteriorly we come to the ganglion

Vv'hich in this specinten has become invaginatea togetr.er with

the overlying epiaermis so as to form a pit, A cross section

t'-.rou^h this pit is s ic vrn in ^ii,, 44 (b) , The cavity o +' the

the
pit is lined by epiderrriis, while peripherially v/all of ti:e pit

consists of the i:ajri;^lion cells and the nerve fibers of the gan-
glion, (T'igs, 3b-44(b) ) The nuclei of the ganj^lia are easily
made out but it is oiily after stainin.^ yery deeply with iron
haematoxylin that the cytoplasm ceuj be seen. Trie invagination
in the region of: the gani_^lion is unusual aria is brDUi_t;t about

(55)

by tt:e violent extraction of the ho oa v.r.en emersea in the fix-
iru^ -fluia. Tiii b unaov!btediy is the saire condition that Master-
TTian (15) nas described and the s azrie structure that ne i;ag hor;iol-
ogized to the "neuropore" of the Chordata or that he has com-
pared to the tubular aoraal nervous system of the same type as
that of Balaiioglossus. (Q J vol. xl , P. 295,296) It shoula
be mentionea, h.o'.vevor, tiiat Kasteraan (16 b) in do answer to
Roule hs.s adJTiittea the error of ..is rather hasty conclusion.

Menon (17) has recently described a tubular nerve ganglion
for a eerv-i.in Actino trocia. but I must believe ti:at the struc-
ture is uue to fixation.

Immediately posterior to the ganrlion a cross section
shov.'s two thickenings of the subepideriral nervous system. These
•hicKenings are what Masterman has describea as the dorsal long-
itudinal nerves and they can be traced from the ganr^lion. They
are almost exactly betv/een the dorsal muscle tract and the epi-
aer-is o^' tj:e aorsal wall, A little farther back these so-callc;
nerves are net quite as distinct but wh.en tne region of the
'Irst pair of' tentacles is reached they become more prominent
again and diverge, passing do;rn the lateral walls along the ba-
ses of the tentacles. (7ig.4l) They meet in the ventral region
said thus form arin^-like thickenin;^ of tne subepiaermal nervous
system which is ujidoubtealy the same tiat ATasterman has de-

(06)

scribed as ti-.e "collar nerve rin.J' . ("Fit;. 4k) GanjrlioTi cells
are demo-nstrable iu thi« nerve ri Uj. by atainirit deeply with
iron haeiratoxylin. (Fii^^,59) Ah 1 siia! ]. aescribe in the ac-
count of the muscular sy^item there is a rin;^ of muscle fiber
v.-hich ■f'ollows the nerve rin.;.

Mastennan says that "fibers pass mid-dorsally as a pair
Q-^' tracts iiivin^ off branches to the body-wall and terrninatinc
in a nervous rin;^; just anterior to the perianal band". Ir his
fi^-ures o"^ sections, hov/ever, the pair of tracts ao not siiov;
back 0^ the most dorsal pair of tentacles. In Actinotrocna
Species, B. , there are no definite tracts 0 1" nerve fibers nin-
nins^ longitudinally from the rei_;ion where the collar nerve rinc
passes obliquely downward from the dorsal surface of the collar,
llerve fibers are undoubtedly present all alonr the dorsal v/all
but these are not massed, together in tracts and are simply the
fibers of the ordinary subepidermal nervous tissue.

The nervous ring in front of the perianal band is rjo t
present in the Actinotro chae that I have studied,

Llasterman (15) finds that part of the nerve rin<^ around
the edge of the hood passes up to the nerve gan^^^lion wiien it
reaches the insertion of the hood and that numerous fibers also
a,ppear to pass on to the ventral surface of the collar region.
Live Actinotrochae (Species, A., and Species, B. ) when examined

(67)
under the microscope do not show a brancVi of the nerve rins of
the lobe passinr upward to the nerve ran^lion. Sections also
fail to show this condition which is very necessary to Master-
man's comparison of the nervous system of Balanot;lo ssus and the
Actinotro cha. ■Fitcr-D frcm i ae nerve ring do, however, pasa
en tc ventral surface of the collar region.

Numerous fibers which Masterman speaks o f as passiu_, down
on to the ventral collar wall are massed in the Actinotrocha
Species, E. , into tv© definite thickenini;:s v^ich are seen in
nr. 44. (c) and 7ic. 40. These thickenings o -^ tl:e nervous tis-
sue gradually a,pi.roach one anotner as v/e trace the sections
backv;ara aiid come to run alon^. the same line as do the two ven-
tral muscle tracts of the collar, but before the line of inser-
tion o-f tne ventral tentacles is reactied, these tii ickeniui^s are
lost in the subepidermal nervous tissue,

I ftave not been able, to make out eitner in sections or in
surface mounts any definite nervous tract nmnivKv; from the col-
lar nerve rin^. alon^j the ventral re^^ion of ti^e trimk, althoupi
as I have said before, there is a subepidermal network of ner-
vous tissue throui-,;hout the wall. It will be r erne rrbe red, how-
ever, thiat above I have described two loni_^itudiXial dorso-lat-
eral tracts of muscle fibers and there are quite numerous longi-
tudinal muscle fibers in t.-e vcr^tral v;all of t r.e trunk. There

(56)
is also a fairly vrell developed layer cf circular muscles am
these together v.ltk trie Ioih.i tudinal muscles t^ive the appear-
ance iii surface views of tlio longi tudiiial tracts ^iviiii^ o f ^
bran ci.es.

The iiervous system o -^ t;ie Actinotrocha of Phoronis Sabat-
ieri is less hij^hly developed, jud^in;^ frorr: the specimci^s I
have examined, than tnat o -^ either Species, A,, cr Species, B.
The i~ani;lion or as Roule (20) Cc<,j.xs it ::...« "plaque cSj^iiali qu e"

eoiitains {^an^lion cells like ti.ose I have found in other Actin-

present
otrocha.e, v/hieh shows that ti-.ere is something mo re^ than a sim-
ple subepidennal nervous system, such as Houle has aoscribed,
in ohe Ac tinotro ciia of Phoronis Sabatieri,

Muscular System:- Tiiere is no doubt but t-iat there is
some diversity in the arrangement of muscle :*^ibers in the dif-
ferent species of Aetinotroci;ae. A stud-; of tiie two Species,
A. aiid E, , as well as ti:e description of different species by
other ivivesti^ato rs convinces me of this.

In my study of ti:e muscular system 1 have had best results
with material fixed in "Plerriming 's strong solution ana stained
with Haidenhain's iron haematoxylin. These solutions make the
muscle fibers stand out very distinctly, whereas material fixed
a,nd stained v;ith other fluids shows them so feebly that the
muscle tracts might easily be over-looked.

(59)

Ikeaa (9) x.as described a pair o "" buiidlea of inn.scle fibers
B-pririt.iiif, f-'"om "ttvc iiiiia lateral coriicrt of ti:e ^aiiijlioii aud
rTJUiiiiii, divergently aovnr.vard until they insert t he rri-y elves in the
collar walls tetween ti:e -f"irst aiid secona teiitacles". These
im'scles, to which he has triven tno name of "retractors", are
present in the Actino tro chao Species, A., ana Species, E. ('Pit.s.
34_35-45-45(a) )

The "retractors" tr.at Ikeaa fij^ures in the trunk cavity of
one of tie Japanese ActJ no troc r.ae 1 am unable to -^ind in either
Actinotrocha Species, A., or Species, E.

Another pair of bundles of muscle fibers is fbuna in Spe-
cies, E. They sprin, from the wall of the hood at the sides
of th.e ganj-lion, traverse tr.e cavity o^ the hood aiid be-
come inserted on its ventral v/ali. directly under thie
f^aui^licn. (Fit:.45 (a) )

Certain tracts of muscle ■f'ibers are very hi^^hly developed
in Species, E. Transverse sec t ions ( staine d witi; iron haematox-
ylin) throu^-n the v/all of ti^e iiood in front o ■f' tiie j^anj-,lion shew
blacK dots spread over tiie internal dorsal surface o -^ the hood
and these seem to be imbedded in the iissGdenrial linin^^. These
dots are the cut eijds of muscle fibers and as th,e sections are
follcv/ed posteriorly, tt.ese dots ii,rad\jally become massed about
ral-^ way betv/een the j^.aiii^lion and the sensory papilla and rep-

(60)
reseiit the sectioned ends of a pair of lont;i tuainal muscle
tracts which are bilaterally placed, one on each side of the me-
dian dorsal line. (■p'ifc;.44) These two thick tracts of muscle
fibers extend posteriorly in the do rso-lat eral regions o -f Uio
Actinotrocha and do not disappear until the perianal rin^,- is
reached. They are very characteristic structures in Species, B.,
(■*''i5S.44 to 4-r(h) ) but 1 iiavc not been able to make tr.em out
in Bpeci es , A.

These muscle bands, no acuLt, servo to draw th^e anal end
0"^ the body o -^ the Actinotrocha up to ti.e oral end duriiij^ tiiO
metamorphosis. Tiiey are tne most hii-;,i;ly dovolopea muscle tracts
in the body of the Actinotrocha aiid their course is alraost iden-
ticsl ".vith ti-e course of the "dorsal nerves" tnat kasterman de-
scribes.

Exarriinat ion of cross sectioi;s of Species, B. , in ti:e ro-zion
of tne vestibule shx)<vs the cut ends of numerous muscle fibors
v/i\ich are spread over the ventral surface cf t^.e collar. Passing^
posteriorly, these fibers become massed into definite muscle
tracts, about half way oack from the vestibule to the ve-nt ral in-
sertion of collar- trunk mesentery. (Ti'i^s . 44( c) -44(d) ) Tnese
two ventraJ lon£:i tndinal tracts which are bilaterally placed
one on eacr. siae of the ventral median line become separated, in
most cases at lea-;t, from the vevitral body wall in trie rej_ion of

(61)
the posterior pair of blooa corpuscle Hiasses ciirj. tue latter be-
come rati.er closely associatea v/iti". t i'.em. {'Fi^.AC) 1 couli not
discover that tliese fibers were ii^ any way related to tr.e ne-
pkriaia as has beeii aescribea for some species.

In the re^^icii o-^ tne insertion of tke ventral tevitacles,
the muscle -fibers of the ventral tracts become a^iain applied to
ti.e ventral body wall but definite tracts are no lovii^er present.
However, in the trunk re^iion these fibers form a definite tract
which is coij-^ined to th.e veiitral body wall and it does not dis-
appear uiitil the perianal rin.: is reached. CPigs. 44(g) - (j;) - (i) )

/jfiOther tract of muscle fibers preseiit in Species, B. ,
wi.icl: does not seem to be developed in other Ac tinot roci'-ae,
judi^in.; from existinjj descriptions, is tiiat found in the re-;icn
of tt:e bases o +" the tentacles. "^rom the dorsal muscle tracts,
where ti.e most dorsal and ai.terior pair of tentacles arise, mus-
cle fibers are ^-iven off wnich. follow the bases o-^ the tenta-
cles and wnici^ form a well developed rin^, of muscle ^^ibers; in
oth.er words, there is a ri H;,, of muscle fibers wiiich follov;^ tnc
line of insertion of the mesentery between the collar and tnink
cavities. ("^ig.44 e)

A tract cf muscle fibers v.iiich also sssms to ccc-'r only
in Species, B, , is one compcsca of only a fev; fibers which are
found runiiing arx)und the edge of the hood on the internal wall

{Ok)

of tke same. ( T-^igs. 44- (u) - (b) - ) Y^nere tr.e edt^e of tne hooa

j.c(,cib:.o iiitu tri-^ wj.i.j. v^f tl-.c collar cavity tneae fibers are seen
to nni 01. tc the interiial surface of ti.e lateral wall of tl.e
collar ai-id to miiij_;le fi-ijally with the fibcrj ^f the aorsal tract.
The ciirectioii these fibers take v/hen they pass on to tr:e wall of
t!-e collar remivids otjC vorj much of the fibers \'.nicn Mastoraaii
(15) figi'rea as nerve fibers.

On the interi.al ventral surface of tr.e hooa in bo ti^ species
of /^ctinotro Ciiae, there is a system of muscle fibers arranged
concentrically. They run almost parallel v;ith one another and
with the edre of the hood. (Fii_;s.47 and 44(a) )

Beside the tracts of muscle fibers v/hici-. 1 have described,
ti'.erp are, liniut, the walls of the collar and tnjniC, circular
muscle fibers lyin^; between the lon-itudinal muscle fibers ana
ti:e ectoderm. These have been t^enerally obse'-ved by previous
v.'orkers as have also the muscular coverinr of the ventral poucii
and the muscle cells of the dorsal blood vessels.

Bo dy Cavi ties, Mesont en. e_s , e tc . ; - Muci; dif^^erence o-^ opinion
exicsta as to the orisiin and limits of the boay cavities in the
Actinct '"ccha and also as tc the value of these cavities in deter-
iniiiin^ tlie phylogenetic history of Phoronis,

Roule (£0) stands aloTie in considerinr the Actinotrocna to
aave but one body cavity 'M:ich is lined by an epithelium formed

(63)

from mesencfiymatous cells. He absolutely denies ti.e presence
of any iiiesenteried,

Tiiroui/h the kindness of Mr. Longchamps I have been able to
study tlie Actino t rocha o-^ Phoronis vSabatieri and have founa tl:at
the iTiesent er-y bet«ee© tire (e*)llar aiua trunk is i; resent althou^jh
it id less kighly developed tlian in ctiier species. I am unable,
..iti: ti-.e material at hand, to tjive any opinion as to ti.e i^res-
ence of a mesentery between ti.e preoral lu bo and collar cavities.

Caldwell (3) claims tuat there are but tv/o body cavities ana
tiiat these arc separated by a mesentery (coilar-tr-nK mesentery
0 f Masterman) ,

Lon£,champs {12) 3d -"ncxinva -^c./ard the view of Caldv/ell
..biio Ikeda (9) finds the mesentery diviain^ the lube ana collar
..i'lcn, liw.7Cvur, he says, is incomplete. Boti; of ti^.isa investi-
j^'ators recoj^ni2;e the presence of the ventral mesentery,

Menon (17) t-'nas '.nree body cavi ties , (preoral, collar and
trunk) a ventral mesentery and indicatioiis of a dorsal mesentery
in the trunk,

MasteriTian (16) considers that the Actinot roc ha have five
body cavities. An unpaired lobe cavity, a paired collar cavity
and a pairea t-vnik cavity. This idea is based on his study of
tne early aevelopment o -^^ tne body cavities aiid not on the adult
organization of t'ce Ac tino tro cha, -^'o r in the colla-- ne finds only

(64)
a aorsal mesenter-y (no oti.er invests jrato r has seen this) and
in the trunk only a ventral mss enter/,

V/hile it is fcssible ti:at the rucsocierii! arises as aivt^rtic-
ula from the enteron, as Caldv/cll and Masterman have described,
yet Lon.;chaHii.s , (12), v/ho nas recently re iiives tii^atea ti.e early
embryoloi:y of the f o rai t/it,^ CctidAell v<c>"Ked on, (Phoronia Kow-
alovskii ) aeiiiLies the orit,in of the cavity in front o -f* t r.c col-
lar triink mesentery from enteric aiverticulu. Ikca-j, (9), vvho
rocot,:niiies the "anterior uiverticula" of Caldwell in ti.o Japa-
nese species, nevertheless holds tnat tne body cavities ao not
arise from anterior diverticula but are simply produced by mes-
oblast cells applying:, themselves to and forrriinr t!;e lining of
ti.e ectcblastic and entcblastic wall.

In the sectiovi on the iresoderm I nave stated ti.at ix^ the
embryo of Pkoronis architecta I do liO t find t^nat me mesouenn
arises from enteric diverticula. There cannot be the least
doubt, ho-.vever, that the preoral lobe at aii early s ta^e becomes
lined by a sac o "^ mesoderm cells ana that tuo wall o ''' tnis sac
i^i ves rise to t iie mesentery. T^rthermore , tr^is sac is extended
postero-laterally into two horns v/hich are characteristic of
tne cavity o^ the preorul lobe, according to Mastenran, Ikeda
and Mencn, It must be admitted, however, tjiat this sac does
not seem to retrain itb caracter as a sac but tuat the cells

(65)
i:.ecome separated ar^ci apply themselves hern aijci tliCre to the \7alls
of ti.e preoral lobe. The mesentery reniains intact ana canuot
be coiiSiderea as a secondary structure as nas been sUi^-ested by
Loncchamps. Mthou^^h 1 at:ree \viti> Ikeda'o statement tnat tne
mesentery between the lobe aiici the collar is i.icompleto laterally
in tre fully developed Actinotrocha, yet in ti-.e Actinotrocna of
Phoronis architecta, at least, it must be cor^sidered as a de-^i-
liite mesenter-y.

The fully formed Acti nc t rochae (Species, A. ana Species,B.)
do not sho',v a complete epitnelial linin^^ to the preoral lobe but
the mesoaerm cells are arran^^ed as I have described in tiie younj.,
larva.

It is statea above in the part on tl:e mesoderm tl;at I do
not find tt^at the lining; of tt-^e collar cavity is o+' enterocoe-
lic orii,:in in Phoronis architecta. However, in tne fully
forme 0. Actino t ro cVia there is an undoubted mesodermic epithelium
lininr the somatic '.vail. This layer is very conspicuous imme-
diately be^^ore metamorphosis because it becomes separated from
ti;e somatic wall prior to becomint^ transfcrmea into tne ri tit. ves-
sel of ti.p ,.ault. (■Pitrs.51(t:)-51(>i) )

The splanchnic wall of the collar cavity in t iic Ac tino t roci:-
ae that I have examined is devoid of a mescderirial linin^,^ and the
occurrence of me",soderr;i cells on t>ie wall is verj infrequent.

{66)

Tiiio conaitioii o ^^ affairs in the well develc:. ou Act iiio tro cha
d v.'iiat one would expect froiri trie dispositioii of the raeaoaorrrL
-dis in the vory youii-^ larvae o +' Pnoronis architecta where it
iy Ciily verj seldom trat any are foiuia en tn_ at^aach wall,
(Fit.:. 24)

The absence o"?" a mesoaernial liniUj^ on tl;e splanchiiic wall
of tiie collar cavity is maae all tke more evi aont ty tr.e exami-
nation of cro3:j sections sho^vin^ ti=o colla.'' trunk mesentery,
(Fi|_^3. 51 ({:) -ol(it) ) Wi^ien tfie mesentery reacnes the stomach
wall, instead of dividing into tv/o layers one»o"*^ wfiieh \\ould be
continued into trie mesodermal linin.., of the atoniacii waxl of tlie
c^i.j.ar cavity, it turiio abruptly upon itself and becomes tke
lii;iri^ 0"^ the stomacn wall o "^ ti.e trunk.

I have iiever founa the least iiidication in tke collar- cavity,
0 "l^ a dorsal mesentery such as I'asterman (15) has described in
the Ac ti no tro cha -from St. Andrews Bay,

The trunk cavity is lined throut^hout by a sac o •*" mesodermal
epithelium and the mesenter:, is plainly seen to be continuous
with the lining of the somatic wall and wi tr. the linin^, of the
wall o f the gut.

The ventral mesenter-y of the trunk is; preseait in Species, A.
and. Spe'cies, B, , and vrhile there is no aorsal mesei^tery, I /-.ave
found indications; of it in t to specimens only (Species, B. ) at

(<>7)

tAe posterioi- ei.c; of tke truixk. 1 caunot say, however, tnat it
-as any ontogeiaetic .ii t,ni f i c aiic e . ("Pii:^. 48-44(i ) -44(i-^ ^ I have
also founa tue vr-i.tral mesentery to be present in tue Actinc-
troci'.a of Phoronis Sal)atieri,

The veijtral poucn fills a lar^e part of tne trunk cavity in
the fully fonrted A.ctinotrocna and just before mc tamo rpvio sis ,
it frequently puswes tire collar trunk rueaeiitery v/-ell forwaru
into ti^e collar cavity, tniis makint, tJr.e stuay of tue relation of
tt-e different parts quite aifficult. Bo tr, tr.e external opening
of the ventral pouch and tf:e nepj'.riaial openiiij:,3 are found on the
ventral v;all o "^ the trunk just pooterior to tiit iiiaor-
tioi 0"!" the TTiesentery as in other species,

IlepiirJ gja;- V/agener (^3) was the first to observe tr.e "ne-
pkriaial bouquets" but Calav.'ell (3) was the first to publisn
a caref\jl stuay of tue nephriaia of ti.e Ac tino trocha,

Crooarici; (6) x^as receiitly published a paper on t'-,o excre-
tory organs of Ampkioxus aiid rie aads a njt2 un th^. nephriaium
uf the Actinc trocha v.l. ich ccnfirras Caldwell's vie\v. The t .."c

latter investigators agree that the ne;.firiaiuiii ends blinaly v/i th-

eacii one
out funxiels , that there are tubuxa.- pro i;esseo^;;on-ain- n^^ a.

that tnesc processes
lumen ana tipped v/ith aii excretory cell and ^ radiate out from

the blind inner end o -f the nephriaial canal.

Iont:,C-'.amps tlZ) is inclines to accept Cald.vell's view of

(b&)

the subject, Roule (20) ana Ikeaa (9) seem to iiola tr.e view
that tke neps-.rilial caiial eiido bliualy wituo^Jt brancuiii^^ ana
that the bliiid cr.n is tipred wi ti; excretory cells, v;hich, i-\o\-:-
ever, are iio t perforate,

Masterman (15) x^i^ Vi-^i^c.-^i (17) have anctner view, Tiiey
bo tn tniiiA ti.c.t ti.e nepkridial caual teriaiuates iiiten.ally as
tv/o (Menon) or i;io re (Mastern^an) funxiels aua ti.e:^ recot^i.i^e the
existeiiCe of lorii-^, processes v/ithout luiiiejja attached to tue
eiids 0^ the fura.el,

I have Tiot been able to make a study of the liviii;, i.ephrid-
ia o-^ the Actinctrocha but 1 nave iiives tii^ated them by meariS
of sections in Species, A. and Species, B. "P'o r this ^.Trpose
I have used material -^ixed in ■Fleirimint, • s fluia ana also in
corrosive acetic. Tiie sectioxis were stained v/i tn iroii naema-
toxyljn. Tly 'work has beeia aoiie with very r.ij^h. pov/ers.
(Zeiss obj ,7_^id llo, 12 Zeiss ccmpensatinji occulare)

The nephridia o ^" tiie tv/o Actinotro chae nave much the same
structure but in Species, A.., I h.ave been unable to find that
the internal ena of the nephridial canal brancr^es while in Spe-
cies, B, , the inten^al end diviaes into two short branches,

■^ij^s. 52-52(a) -52(b) represent th.ree trails verse sectioiiS
throuf.h the anterior part of the nephridium of Species, B, ?i;£,
52 is throUi_.h tbe nephridial eanal just posterior to its inter-

(69)

iial end. Darkly staiiiin-, dots seen in the luir.en represent

cross sections of Icn^, flarella sucii as Gooaricii (6) i.as de-

scriboa in the "solenocytes" of Amphioxus,

■p'ir. 52(a) shows a section through the liephriaial canal a

fev/ sections anterior to that of l^'itr.SS and at the same time

it shows the lower or most posterior branch with a few excretory

cells and their processes,
whi ch i s
In Fii-,52(b)^a section trirout,h the tip of the upper or

BXiter-icr branch of the nephridiun:i, the lumen of the nephridial
canal is reduced to a very sji.all clear space.

If a section is taken in a loii(.,i tudinal direction tiirouv^h
the nephridial canal and its excretory processes ( T'l^-. 52 (ij) ),
it is seen that ti;e distinct walls of the nephridial canal dis-
appear when the "bouquet" of excretory cells is reached but that
the end is blind 8.nd that it as merely a thin walled bulb from
v<hose sur-^ace radiate the processes of the excretory cells. The
St nocture of these processes is the same iii both species tiiat
I have examined except that in Species, A., they are ve r/ much
shorter, which. xitfl^»f?a»i»Q£ mi i_:ht account for tr.e different ae-
scriptions we find in trie literature. 1 am convinced that in
both species the excretory processes contain lumens, that ti.eae
lumens are continuous with t hje lumen o "*^ the nephridial canal and
that they contain flagella.

(vo)

Each of tne excretory processes is tip-eci by a body, the
distal end of whicii is drawn on.t into a shari. pointea process.
I have been unable to see tiie outline of more tnaii one cell in
the body, Sornotimes it contains but one nucleus "vhich may be
oval in shape or bent almost at y-i £ht ai.trles (T'ir. 52(d) ) but
in the majority of cases there are undoubtealy tv;o nuclei,
(Pig. 52(c) ) Fig. 52(e) shov;s a cross section throui^n one of
these bodies. If a transverse section of tne nephriaial pro-
cesses is t^en(Fijj . 52( i) ), it is seen that each has a definit;
wall and that inside there is a definite dot which I take lo be
a cross sectic"n tn'*,''''^L. '^x. /lc£iellum. This fxa^j,- j.j.';ia hcta i'^o
„'"it:Jn from th" cell bv^d" rj.t the end of tne process aaid the in-
dications are that the flat:,ellum extends throut^icut the len^rth
O'' the process into the lumen of the nephriaial tube.

I am not prei.area to say that the cell bodies at the end
of ti.e excretory processes are ccmposea of t v.o cells but it is
a fact that two nuclei exist ana 1 have not drav.n this coi. elu-
sion from sections throui^i: bent nuclei which mifc^ht lead one to
think that there were tvx) v.hen only one existed. It v.dll be
seen from this description that the anatomy of the excretory
cells 8jid processes o :!'■ the Actino tro chae v/hich I hcive studiea
resembles that of similoT- structures described by Goodrich for
Ajiiphioxus.

(71)

I have nothing nev/ to aaa concerniiit^ the liephridial cai.al
except tiiat a loiiti tuainal section thirout^:h it which has been
stained 7;i th iroxi haematoxylin shows lon^ fla^ella extending
some distance from the ais tal end into its lumen. (Fi^, ok;(j..,) )

Sections which 1 have made of the Actinotrocha of Pho ronis
oabatieri show that ti.e i'Opi:ridia resemble those of otner Ac-
tinotrochae 1 have studies, althouj^i. they do not seem to be as
well developea as tr.ose o *^ Species, A. and E. The speciinens
at hand show that the inten.al openin^^ in the collar cavity is
situatea at about the saire level cts in other Actino t roci^.a? i*na
not at the level of the oesophagus as rioule (20) has indicated.

The course v/hich the canal taices i^ like th^t v/hich has
been describes by other invosti^ators and I a^ree v/i tt. tae ob-
servation of others in re^jard to the nephridial canal openin^:
to the exterior at the sides cf tne ventral pouch opeiiiiit,,

Masterman (15) describes a pair of ciliatea pores openint^
to the exterjor on the dorsal stirface of tiie preoral lobe.
These, he finds, lead into tubes closely similar in cross sec-
tion to the cross section of canals of the collar nephridia ana
these tubes have an internal openin_, into the preoral lobe cav-
ji.y. He compares the external pores to the proboscis pores of
CephalodTiscus. In the Zoo. Ajri2iir.-1901-vo 1. xxi v-p, 251, he ad-
mits that their :oc cur rence is variable. llo other investigators

(72)
have fbijxia these orfiaus. Ikeaa meatioiis the fact tliat flaak-

shapea fc,lai:ds on the upper face or the preoral lobe occur in one
larva otudied by him but he aenies that they are auch ori^ane aa
MabtenTian describes.

Maatennan (lo) also finas thin walled organs lyings in the
haemocoel space iirunediately belov/ the anal ciliatea bana. Speak-
ing of these (15) he says: " a pair of organs whach I have not
fully maae out, but they inay be the ruaiments of t ne t runK ne-
phriaia". Masterman, hov/ever, denies their existence in a la-
ter paper and no one eldc has seen the organsas far ati 1 know,

Ruuim^nta of the Adult Blooa Vessels in the 4ctinot rociia ; - Many
investiga.tors of the Actinotrocha have recognized the beginnings
oV the adult blooa vessels but E.B. V/ilson {24) is the first one
who clearly states the fact that the cavity containing the blooa
corpuscle masses gives rise to the ring vessel of the adult al-
t l".o u gh i«e t s el:! n i ko f f s e em s to have r,a a so me such an idea,

Caldv/ell (3) and Ikeda (9) confirm the statement of Wilson
ith reference to the origin of the ring vessel of the adult.

V/hile Fasterman (15) aescribes a much mere complicated vas-
cular system for ti:(i Actinotrocha from St. Anai^ers Bay than that
of all the Actino trochae v.hich 1 have examined, yet 1 agree vvit.h

im in his view triat the cavities of the blooa vessels may be con-
sidered as vestit^es of the segjrentation cavity.

(75)

Above 1 have given ray opinion that tl:e "subneural sinus"
(Masterrrjan) ao es not exist in t tie Ac tino trochae t]:at 1 have ex-
ajflinea ana that althou-^h there is a space beneath the ganglion,
it has no connection 'Aath tne dorsal bloou vssLiel,

The blooa vessels of the adult are represented in the Ac-
tinotrochae Species, A. anci E, b;' a aorsal blooa vessel CPigs.
34-55) extendin^:; alon^: the meaian dorsal line of the int-^stine,
from the niesentery between the collar aixa trunk almost to the
posterior end of tne s torriach, vvhe re there are small caecal out-
pushin^^s of the splanchnic mesoder^ial v/alls o "f' tiie ena of the
stoTiiach. This dorsal blooa vessel, althou,,h it is a con.pletely
fon^ed vessel, has arisen from a proliferation of the cells of
the splanchnic iLesodermal wall along the dorsal meaian line of
the stomach and its lumeii is really a part of the bias tocoel, i, e.
it is a part o-^* the space between the splanciinic mesoaern.al lin-
ing: and the v.'all of tr.e stomach. Posteriorly, tne aorsal blood
vessel becomes indefinite and passes into the orainary splaiich-
nic mesodermal lining, thus really bein^ open posteriorly into
-he space between the wall of the stomach and the inesodermal
lining.

At the time of metarro rphosi s in the Act Jnotrocnae Species
A. ana Species, B. , tiiere is no sign of a ventral blooa vessel
■long the stomach, such as Masterman (15) and Houle (20) aescrib^.

(74)

1 nave been urjable to find the "rii.;^ sinus" valiich, accora-
inj: tc Masteririan, connects tne aorsal veasel witn the ventral
vessel at Zh<^- euOi of the stoniach, iio r have 1 seen ti:e "postoral
rin^: sinus" conijectinj^ the aorsal vessel with t):e veritral vessel.

1 shall discnss Mas t e rrnan ' s "post-oral rin^: sinus", "ven-
tral blooa vessel" ana "rin^, sinus" (siti'atea at the junction
tet-.v^^n the stomach ana intestine) in the section on the metamor-
phosis,

Th-re is unaoubtedl- a space betv/een ti:e wall of th.e peri-
anal ring and its mesodermal liniui,, (Fig. 49) in preservna spec-
imens v.nich 1 suppose is wnat Ivlaster.aan calls the "n.*Pi:io.l rin;-,"
but it aces not become any organ of the aault.

As otatea above, 1 believe v/ith Wilson, Caldv/ell aiid Ikeda
that tiie ca.vi!ty of the collar and its somatic ineBodermal lining
I -^ CO me thp- rin^^ vessel of the adult.

I shall continue the discussion o -f" the furtner development
0 -f" the dorsal blood vessel into the efferent ana afferent veooels
0 ■•■ the adult in the section on the metam.orpiiosis.

Mastenxian speaks of haemal sinuses passint, dovm the tenta-
cles but says that they are not very aeciaea. Ikeaa nas ,ho 'vevejj-
investigatea these structures carefully ana I thorou:^yiily agree
v'ith his view that the cavity of the collar together v/ithi its
somatic lining extends into the tentacles anai tiliat these proloag-

(75)

f atioiis become ti.e t entacniar vesciela cf the aault. Thi.ti coi-
dJtion is aho'.vn very plaiiily iii a aorso-lateral Bcction o J" the
ActiiiG trocha Species, A. ("Fif^.oO)

Blood Corpuscles aijd Their Origin;- E.B. ?/ilsori (24) has
tou.cheu upon the oritjin of the blooa corpuscles ana accoraint;
to him, the blood corpuscles uevelop in soli-a masses aai:crinj_: to
the stomach walls near the base of th.e tentacles.

Caldwell (2) finds that the corpuscle masses "arise from
the mesoblast cells in front of the septum" but he has no thixig
:^urther to say about their position or origin,

Ikeda (9) aescribes the blooa corpuscles as arising, from
"gigantic mesoblast cells in the body cavity of the larvae witii
one or two ^loiirt, of tentacles". Since the publication of tnis
aper, Ikeda has re^^ect^.d ti.io view although he has published
c thing en the subject,

Menon (17) thinks that the blooa corpuscles arise -from the
splancnnoplpure covering the sto'.nach and its diverticulum.

Accoraing to Cori (4), the blooa cor^ubcles in the adult
are formed from tne endothelium of the blooa vessels.

In the Actinotrocha Species, A,, (probably that of Phoronis
architecta) the blood corpuscles usually make their appearance
aurin. the l4 tentacle stage, as in "Type A" aescribed by Ikeaa,
although I have founa larvae of this stage in v;hich definite

(76)
blood corpuscles were not present.

Actiriotrocha Species, A. with 16 tentacles invarj ably has
blooa corrus.cles and they are present in the so-called collar
cavity as tv/o i^.asses more or less closely api-liea to tne ventro-
lateral walls of the stoinach. ( "Fi^^o. 51 (^J - (h) ) In some c<a.-
ses, he ■■.•over, they are t,*^ puratea from t^ie v:all by a considerable
space.

The transverse section of a larva with IL ter.tacles in a
plane j"^t :c..torior to tne base o f the tentacles but cAiiteriO'"
to the mesenter;'^ a.lv;ays shows two masses of cells bilaterally
plucea ca^a closely applied t. t.a'^ m:o„acn:n lining, the ventro-
lateral somatic v/all. ( ^i ^ . oo ) Occasionally 1 have founa cells
in these masses situatea very close to the mesodenral linin.,
which "-ere uecidedly spinale-shapeu in form and v.'hc ^e nuclei re-
sembled 1-hcse of the cells o *' the mesodermal linint^, both in
sha^e, size aiia internal structure. These cells are -uo t very
rich in cytoplasm, Most o "^' th.e cells, hov/ever, are almost
tiiree times the size o f the cells linint^ the somatic wall, the
cytoplasmic part of the cell havin,-, increaseu in size to a f^reat-
er extent thari the nucleus, Iv'ost of the nuclei have large deep-
ly stainint, nucleoli. i'^^^t.-^^^)

In some specimens, parts o "^ these masses of cells are appar-
ently in the act of wand"Hn^ across the body cavity lo the posi-

(77)
tion t:e ulooa ecrruscle masses occupv in one fully fonneu Ac-
tinctroc'ia,

1 have secLionea some lo or 20 larvae with 12 or 14 tenta-
cles and with one exception I have found that when tne mesodermal
masses are present on the ventral body v/all, tiiare are no blood
corpuscle masses present in che larva ana that when the bloou
corpuscle masses are present, ti.ere are no mesodermal iiiasses.
In the excer.tiov- which 1 have mentionea, small ulood corpuscle
jaasses were found applied to the stomach wall and masses of
cells bilaterally placed v/ere found on the ventral somatic wall
but these cells had already taken on the character of blooa
CO rpuscles,

Ikeda (9) has described a "irieso bias tic cell mass" viiich he
evidently considers as givin.; rise to tne aaulL boay cavity and
its position is verj similar to that of the laeso bias tic masses
that 1 have described above. They are both products o'*'" ti.e mes-
oblastic lining- of the ventral somatic '.vail and are situatea be-
tween thiC plane of the bases of the teiitacles and the plane of
the somatic ii.'sertion of the mesentery betv/een the collar axid
trunk, Althouc^h Ikeaa aoes not touch upon the very early ori-
,,ij' 0"!' the adult boay cavity yet it seems probable that h.e con-
siders i t as arisin^^ from a sinj,;le mass of cells. The meso-
blastic masses that 1 have described above are paired and b-i-

(7t)
laterally r-laced oiic; they are rreseut oiily in Lfie youn. larva of
11^ or 14 teiitacles. '^rthermore, in t.te larva with Ik or 14
tentacles, there is no sirn of the beginning of the adult bocty
cavity. /^Ithou-h these ne no de rmal masses v/hich, accorain.^ to
niy observations, ^ive rise to the blood corpuscles, have a simi-
lar position to the funaament of the younfj adult boay cavity yet
1 aiT! coi'Vinced that they uo not i^ive rise to it.

In Species, A., there is no iiitimate relation between the
masses of blood corpuscles aiid the nephridia, such as has been
described by Masterman (15) f 'o r the species from St. Anarev/s Bay

and by Lon,:chyjnps (12) for Actinotrocha branch! ata. In tlie lor-

bloua corpuscle masses
va of 10 tentacles the , are, hov/ever, closelv arclied to the

Stomach wall in the re^^ion of the digestive area. There is no
mesoderirral epithelium covering that part o f t he surface of the
stomach v.hici'i lies within the collar cavity ana liz^ blooa cor-
puscles se«!m t,r be so intimately relatea to the di;_,estjve areas
tliat 1 sjri iiiclined to lielieve tnat they receive nourishment from
them,

7/hile the blood corpuscles vary in size and undoubtedly mul-
tiply by karyokinetic division yet T have never found the "largo
and some\7tiat coarsely granular" and the "smaller finely granular"
i; corpuscles th^t Ikeaa (9) spea^'S of nor in this species nave 1
■ound any "gigaijtic mesoderm cells" in the region of the blood

(79)
corpuscle masses. Very large colls in close relation to the
bloc-j corpuscle masses are founci in some specimens of Actino-
trocha Species, B. ("^ig. 44(f) ) These cells reserr-ble the cells
\rhich I described in the old ^'astrula of Species, A., as arisinj^
from the wall of the arete nteron, only they are not as coarsely
graiiulo.r as the latter. W.iile in Actino trcc.'ia Species, E. , the
cells are ■f'ound in most cases closely associated v/ith tiie blooa
corpuscles, I have never seen ti;em in the process of division
and 1 do not believe that they ^.jive rise to blood corpuscley.
Their occurrence is quite variable but as far as 1 have cbservea
ti''.ey are not presoiit in trie Ac t Inot rochae which are ready to
••letamorphose. Tiiey are not phagocytes nor are they pigment
cells and the only name which I feel justifiea in givinf, them
is large free mesoderm cells. ^

Frequently they are also founa in the posterior end of the
trunk cavity. ("Pig.44(i) )

Roule (20) holds that the nephridia ena internally at the
level of the Oesophagus and he siio'vs this in a figure, 1 have
made cross sections throu;;'. this region ;ana have founa masses
of cells in much the same place as Houle has shown. These cells
ocem to me to be blooci corpuscles but I must say that I have
I ad opportunity to examine very few specimens and only one of
ineso showed th:ese masses of cells.

(CO)
Huaiaieiit of tho "AcJulA ,CQ-lXar-Jlg:Vil^-- (Ii<eaa) Ike da has
observoo a- nieso dermal cell mass on the ventral somatic wall just
under the second tentacle in rather yount^ speciuiens of all tt.e
Japanese Actinot ro chae. He has traced the developaient of ttiis
mass of cells and finds that a cavity arises in it which, before
metamorphosis, becomes .^ui t<^ spacious aiid extends into the ten-
tacles. 1 aia a^ble to confirm Ikeda's vjev; tnat this cavity is
the rudiment of the "adi?lt collLtr cavity" or "suprasei-tal cavity'
o "^ the o.dult as it is usually called. (Pigs, ■30-4L-ol(h)-'iu (b) -
46 )

Metamorpho sis,

Several inves tij-ato rs have carefully describea the external
characteristics o "f^ the me taiiiD rphosis of the Actinotrocha so it
\ is unnecessary Tor me to enter into a aetailed description ,

V/il3on(24) studied the metamorphosis of Ac tinotroc r.ae Spe-
cies, A. and Species, E. , which are founa in ChesaiieaKo Bay but
he did not cut sections of his material.

(61)

Ikeda ( 9) ,. however, has iuvosligateci the internal changes
„hich take place auring me tairio r^hos is ana has aaaea a Valuable
contribution to the subject.

The behaviour durin^: metajrio rphos is of Actinot rochae Spe-
ciea, A. and Species, E. , from Beaufort Harbor aeeiud t^ be quitr
the same as that of ti.c t ■.-,-: Ac t i no t roc l:ae ■.■,'hich Wilson has ob-
servea, and tner-e is little rioubt in my mind but that they are
of the sam*^ species.

As Wilson has stated, the metarricrphosis of Actinotrocha
Species, A. ("T^ig.S4) taxes place mucii m^ "^ ^uicAx" ti.jji tht^*:
V f Sp'^c"' <=b, E. ("'*'ifi.S5) In fact, 1 have never obtained a
completely metamorphosed specimen o -^ the latter, althou,::h many
ti-Ties 1 have found specimens o -^ this species v/ith the ventral
pouch well eva:jinated. (Fi^_^.5o) I have tried to make the con-
aitions favorable for the completion of the metamorphosis by
coverin,; t(:f^ bottom of the aquarium with a layer of sand rich in
diatoms ana also by chant^in-^ th.e v/ater frequently. Unaer these
ccnaitions, ti.e larvae (Species, E, ) would invariably sink to
the bottom and move around on the sand apparently j.n search of
a favorable place to finisii the metamorphosis. Th" ^.atter neve^
occurred, however, althourh sometimes the larvae woula attach
the ena of the ventral poijch to the bottom of tiie clish. In
this v/cLV the cr<^ature woula often remain for days and although

(G2)
the preoral lobe arid larval tei:tacles v.oula aeijeiiorate the anal
end of the larva "/oulu i.ever oecome turned upv/ara oO ad to lie
in clorfe proximity to the mouth.

As I have said before, 1 am inclined to think that the Ac-
tmotrocha S-pecies, F. belongy to an arr^xt v.hich lives under dif-
ferent conditions from that of Phoronis architecta and 1 should
net be surprised if it v;ere found to be the Ac*;iu^' t ^^cha c t ...
u ^- 7/ater form. A-lthou^h Cerianthus cccui's in Beauifi'^rt Rar-
er, 1 have never founa Phoronia Australis asoociateu with it,

Actinotrocha Species, A., as a rule, r;.e tamo rp noses in about
20 minutes CFigs, 56-d6(a) -b6(b) ) ain usually just before this
takes place, it sinks to the bottom of the disii but occasionally
metamorphosis occi^rs on the vertical side of tlio dishi near the
surface of the v/ater, the youn^^ Phoronis rcmaininj^ fixed where
the metamorphosis takes place,

Preoral Lobe and Tentacles;- Usually the larval or aJatui
^L^rt ;^ f the tentacles (Species, A.) ana tn^ ;. ■ .-ax x^be are
sv/allovved auring me tarriorphosis. The proximal parts of the ten-
tacles become directed Ui...^-a oiid Cunstiti?te th:: tontaci;.s of
the c.a^'x-^. They alv;ays ni;mber eigi^teen in the ve.ry youn^ Pho-
ronis (Spocirs, A.) ..ia ^h^-'-o is an indication of tne horae-shoe
arrangement which is fb una in th.e adult. (T^i^;. 56(b) )

The preoral. lobe does not ^ive rigg to the epistome o -f' the

(63)

adult, ^'or as iieiion (17) lias correctly observoa, Ui i s structure
id not i resent in the very youn^ Phoronis. However, ti.e epis-
toirie, '.vhich is of ectoaennal orit,in, soon makes its apt earanco
and v;hen the creature lias 30 tentacles, it is a verj conspicuous
organ. ("Pit:. 57)

Ganglion:- The ganglion on the aortal surface of the hood
is lost when the precrai lobe is swallowed and hence does not
give rise to the so-called brain ganglion of the adult,

Ectoden.-ial V/all of Collar;- Althougl; tne preoral lobe

degenerateb, tne wall o -^^ the collar does not but beccmo^ drav.Ti
:ij.side the body v/ J' t ne yotini^ Phoronis aiiU tcirir, the ..^11 of the
oral end of the gut,

Perianal Ciliated Rin^^ ana Ectodermal Wall of the Trirnk:- Wi lo n

!.'^ critical point in the ?rie taruo rpiiosi s is reaclTed, tnat is, when
tne posterior end becomos dravai up to the region of the mouth,
tl:e perianal ciliated ring is i;sually seen as a pre tube ranee
in that region (Wilson's 'F'ig.lg) but shortly after this it be-
comes dra'.rn iii ;;aid tOt^ethor witn some of the ectoderm becomes the
lining of that part of the rectum -which is near t!;e anal opening,
(Fig.;j£) Tile drav/in^ in takes place to such an extent that most
of t}:e ectodermal wall of the trunk of tiie Acti no t rociia becomes
incorpor^teu in tho wall of ti.o rectum, as Caldwell has observed.

This process-^ together wi t!i the drawing in o^ the ectodermal

(64)

..all of the collar to form the v/all o 1' tne oral end of tiie tjut
seems to cause a ciiaijjje in the position of trie xiephriaial canals,
(See section on nephriaia)

_ Cavity of the Preoral Lobe;- Since tne precral lobe ia
lost durin,: txie metamorpnosi s, its cavity does not take part in
the yti'ijcture of the adult.

Mesentery Between the Lobe and Collar;- This mesentery
do es no t p ers i s t .

Lar V al Co 1 1 ar Cavi ty ; - As has been stated by other in-

vestii-;ators arxl as I have observed the larval collar cavity
-.-.'ith its rnesodenr'.al wall becomes the rinj^ vesoel of the adult.
I shall discuss this or^^an further in the section on the vascu-
lar system,

"Aault Collar Cavit:/;-" (Ikeda) This cavity, v/hich is
founa in the well developed Ac tino t ro eiia, uijdoubtedly becomes
the "adult collar cavity" or supraseptal cavity of the adult,
as Ikeda has described. In the younj^ Phoronis, it is seen as
a cavity v-tiich occupies all tne region anterior to the trans-
verse septum and v-hich is prclongca into the t entac les, (Fig. ob)
It is lined by a mesodenrial epithelium ana it contains the ring
vessel with its tentacular vessel,

-i^i:ilIiiL,Cavi_t:/ and Cavity of the Ventral Pouch:- Those cav-
ities become the-^ infraseptal cavity of the aault

(65)

Ventral Mosent e ry :_-_ The veiitral uicaeulerj of the Actino-
trocna, 1 believe, becomes tt.e mesentery in tr.o aault v.hici: Co ri
calls the "haup tnesent erium" ana which Eenham names the "oesoph-
ageal" and "rectal" meaent '^•^i'^s. Mesenteries are present in the
ver;,' youn,'; Phoronis (just after tiie completion o -^ the .w^^ti^nor-
rhosis) which are founa in the exact position that one would ex-
pect the ventral mesentery o "f^ the Actinotrocha to assume after
metamorphosis, Ikeda's fiy;res indicate that he considers ti:e
lor4:i tudinal miesent eries of the very younj_^ Phoronis to be the
same a.6 the veiitral mesenter-\' oi' the Actinotrocha, for he j-,ives
them the sajne nairie,

I cojinot offer any observation on the orajjiji o f" the lateral
mesenteries o-^the adult except that they are not present in the
very youn,: Phoronis that 1 have examined. They unaoubtedly arise
later in the life fii story,

^J'9Jl''3-S^t-^P?-y^SS'}S^V}-P-Jr-^ Thi y structure is not present in the
Actinotrocha Gpecies, A., so 1 am no t able to t^ive any informa-
tion on the subject. It s'^en.t; to be the general opinion araong
those who have studiea the metamorphosis that it uoes not persist
as an orgaji in the adult.

Digestive Areas:- V/hile these organs persist for some lit-
tle time after metamorphosis, they are not eviaent as organs in
the adult Phoronis architecta.

(86)

Jlerhridia:-,,,,^ Calciwell (5), Ikeda (9), Loi'it,charr.p3 (12) anu
Merion (17) have all observed the chaise in podition of x.ue lar-
val nephridial canals whicn id due to the chaises taicini^ place
during the critical periou o '' the me tamo rp ho sis ana it ij b..

Mite well eotablishea fact that the exten.al enas of the larval
.^ephridial canald ccmo to be situated near the anal openiiit..
(7i;:.59)

Just after the critical period, a cross section t.hroutrn the
aiiterior end of the youni Phoronis ci-its the transverse septum
( "diaphraj^m" , "collar tnuiK mesentery") which runs oblini'^ely ana
passes throuj/n the ST'praseptal and infraseptal cavities. It
shows a transverse section tiirough the nephridial canals //hich
,u,re still attached to the mesente»-y as in the Acti no t rocha. ^''cl-
lo-."Jni_, tho sections anteriorly, the canals are seen to open into
tne uupraseptal cavity ("larval collar cavities", "ring ves; sgI
cl tne aault") ax^a tn'^v j^r^ totill -f'ound in possession o ^' their
excretory cells. Posteriori:^ t.he sections shjov; th.at the ne-
phridial canals leave the septum and pass between tl;o wall and
the mesodermal lininj.; of the infraseptal cavity. (Fiji. 59) At
this time, their exten.al openings are situated on the lateral

;:iaf^rr-:al wall in a trars verse plane which is somewhat below the
transverse plane of the anus and they are by no means as near to
liie latter as they are in the adult Phoronis. It is seen from

(C7)
thia aescriptioi^ tJ.at rlurin^ tha critical perioa, there i -s very
littiT ciir^ise -i ii 'i. .^■f-'-'-c rvr-e of the larval iiOi-hriaia or in
their rositiou, althoiu-jh the evatinat iovi of tt;._ vai"r.-.l pouch
ana the d'-a-.vin.,-. in of the ect^u-— /ri . i' ^i.c triinK to form the ena
of the rectum cauaea the amis to becoiric rather clos'^ly c<.pprox-
imatea to the external ne^J:;;-la1 .-.^ ^^..irxif^^,

Cr-ld-/vell (3) says that the whole of the la'^v^j. n ,,.nriuiL-l
canals rerriainsas the pairea ncphridia o f the adult v/hile iKeaa
thinks it probable that only the parts of the nephrialu.1 canals
lying in the v. all of the trunk persist . He assumes that thie
neph^idial fimne Is of the adult, v/hich both open into th^' in-
fraseptal cavity, are secondary outgrowths of the above reirijiants
of the nephridial canals.

As the nie tamo rpho sis contixiues, sections show ("Pig. 60) that
the excretor;,- cells ana that part of the nephriaial canals sit-
uated in the larval body cavity nave become obliterated tOL.ether
ith the portion o^ the ..e,n."jui,a ca..al.3 running in tnn septum.
While I do not vash to deny th^t the reirants of th^ nephxidial
canals and their exten^al openings, situatea originally in the
trunk cavity o- the Actinotrocha, become part of the nephridia
of the adult, yet in the stage unaer consia^..t icu, I am unable

to ^ina that they exist. So far as I k

no'v, Ike a a is the onlv

investigator ....^.c ,;..» given us figures illustrating tl^ relation

(b6)

,etv,-..B the larval ue.hriala .na U.e .eph. : dl a f tae aault .
While his>i^. 64 e shors the .arval i.ephridia. camls, hi. T^ig.
66, which is a cross section ti'iro^-yy.h the anterior end of a youn^,
Phoronis and which shows a section through the youn,. uophridinm
of the ;^ault, does not convince me that he is aealiUi, with the
same structure,

V as c 111 ci.r S y s t exrr.j-^ It rill be remembered that the vascular
system of the full;' aeveloppu Actinctrocha Species, A. consistea
of a dorsal blooft vessel ('F'igs. 5„( ^ ) - (j^) - (h) ) running alon^j the
mediaii lin-^^ of the stomacli from the aorsal insertion o^ tir:e mes-
entery between tne collar and tmnk to the posterior end of the
stomach, its lumerj beini, a part of the sei^mcntaticn cavity; a
bunch of blooa caeca fo nrxe d at tlie posterior end of the storaach
as evaginationso f its splanchnic me so dermal covering; a loose sac
of mesodermal tissues arisiing on the somatic ./all of t):o collar
segmeut and enclosing the larval collar cavity. (Figs. 50-51 ( f) - (g-)-
(h) ) (See section on the /re tajTiorpho si s , ^or aiscussion of
ii.e "post-oral rin,., sinus", ventral vessel ana the "ring s-in";^"
at til- junction of the stomacn and intestine)

There are several important points in the vascular systezn o !^
tne Actinctrocha v.'-hich must be taken into account in oraer to
understand its metairiorphosi s into the vaac\>lar system of the
young Phoronis. "Pirgt, that the dorsal blood vessel, which is

''ormea from tl:e splarichnic me soder/aal linii:^ o :!" the trunk cav-
ity, ei^cloaes a part of the space betn'eeii ti:e liiiirit: and the
■all of the all merit an/ cand; i.e. the s egmei.tatiori cavity; sec-
ond, that this vessel dv.'indles av/ay posteriorly aaid opens into
Liie space betweeii the linin^^ and the wall of the alimentary ca-
nal; third, that the v/all of tnn storaach in the collar se^^ment
is practically free from .'nesodeni.al linin.^ (Fi^-s, 51 (g)- (h) )
ajid that the larval collar cavity with its soniatic iuesoderj.c:.l
lining is a blood sinus; ^burth, tha,t the larval collar cavity
is a part of the sei^meiit ati on cavity; and fifth, that durint:
irietairiorp!:osis the act of arawin-. the stomach and intestine into
the cavity of the veiitral pouch causes a pressure to be exertea
on the larv&l collar cavit;',

T.'hen the critical s ta^e is beint. passed thj^ou-rh, the blood
corpuscle masses breaK up and tliey are driven by the pressure
on tr>e collar cavity to the points of lea3t retistance. As a
rule, some of the blood corpuscles are squee^iea up into L h.e dor-
sal rej.;ion of the collar cavity where t.ne aorsal blood vessel
-uds and invariably so ire o^ the blooa corpuscles pass from the
larvul collar cavity into tl^e cavity between the wall o *" tiie ali-
mentar-y cajrial and its mesodermal coverin,:. In fact, as soon
as the critical sta^^e occurs, the splanchnic mesodermal linin^^
in all regions bf^comes separated ^"rom the wall of tir. alimentary

(90)
canal ana thus allov/s tne blooa corpuscles lo move abouo be-
:v.'eeu these tv.'o layers tnroUi^hout the extei.t of the a lime n tar y
caiicil. (■pic^.o9(a)

The dorsal bloca vessel (" rued iaiice fas z" (Cori), "efferenr,
vessel", (Benham) ) and the rin^ vesel with its tentacular ves-
sel are corriplptely forrriea vessels at this stage. The aorsal
vessel is still freely ocen posteriorly iuto the space or sinus
betv/een the stomach wall aiid its inesoderrnal covering ana blooa
corpuscles eore carried back aria forth from the vessel to the
vinus by- the contraction ana expansion O"^ the f o rire r. Anter-
iorly the aorsal vessel can plainly be seen opening into the
rin^^ vessel, (larval collar cavity)

The origin q-^ the connection between the dorsal vessel and
liie ring vessel and the man...er iii v:hich the blooa corpuscles
find their way into the dorsal vessel are queBtions whiich have
not been very satisfactorily elucidated, A.c t.ino tro c ha Species,
A., to my mind, presents no grp^t aif-fic'i^ti '^^ in tne way of
understanding how these processes take placp. The dorsal blooa
vessel opens posteriorly into the sac-like ainus arouna the loop
of the alimentar:,^ canal ajid it seems probable :rom an exa^nina-
tion 0+' sections o '' tie critiu^l stage that it is also open an-
teriorly. Assuming that such is the condition, it -.vill open
into the space betv/een t^ie mesoderrral lining and the '-=,11 of tiie

(91)
gut. This space, hov:ever, in in ^'ree. corrLriunic: atiou wit^"; ulie
larval collar cavil:/ (adult rin^ vessel) v/hicj; coutair.s the
bloca corpuscles. Under these conaitions the blcoc; corpuscles
can pass into the dorsal blood vessel from either end.

ITasterman (lo) ana r^oule (5^0) both aescribe a vessel on
ti;e ventral stomach v:ali of the Actino t ro clia. 1 have not found
thiis vessel in the Ac tino t ro ci^.a nor uo I fiiid it in sections
Q-^ the critical sta£ie.

At this time there is but one rin<j; vessel in the suprasep-
tal cavity but 1 cOiiSid""" tjn^t it represents both tne receivinj;;;
aiio aistri butin.:: vessels of the adult Phoronis.

Shortly after the critical point in the metaino rphos J s , t he
n!esoaer'7ial linin^ on the left side of the oral lirai of the "U"
oiiaped alimentary canal be^^ins to sho-.v indie atioiiS of becomiiifj
a blood vessel and when the me tairio rpl'osi s is coapletea, a def-
inite vessel is seenv/hich opens posteriorly into tne spacious
blood sinus arouna the loop of the alimentary caUal. Anteriorly
be-f"oro reachinr the traiisverse septum, it divides into tv/o
branches which run obliquely upwara ulonj^ the siues o-*^the ali-
mentary e3,nal sJmost encirclinf: the same; these finally open
into the rinj, vessel o"^ the supraseptal cavity. ( ''^iij,. JO ( a) )
The vessel described becomes the efferent vessel of the adult
(Fi£s.7b-77-75-6(.) and its branches become part of the recipient

(9^)

As Ikeda has pointed out, the efferent vessel of the adult
corresponds to the ventral vessel which. Mastenrian (15) and Roule
(20) have found in the Acti no trochae before raetano rphosis.

In all the completely metarno rp hosed Ac tino trochae that 1
have sectioned there is but one rinc vessel, but th.e younc Pho-
ronis wiien it is twelve hours old, posses both the recipient
and distributing vessels; these vessels, 1 believe, arise from
the single ring vessel of the atetacio rphosin^ Actinotrocha by the
■^usion of its walls aiid by the subsequent separation o f the tv/o
parts alonj^ tn^ line of fusion.

Masterman in his description of the blood system of the
Actinotrocha speaks of a "rinc sinus" at the anterior end of the
intestine wliich connects the dorsal and ventral vessels. He also
says that there are two lateral branches of the dorsal vessel
in the rej;ion of the pharynx which pass dov/nwara arouna the oe-
sopha^'us ("post-oral rJn{,- sinus") and become continuous with the
ventral vessel.

The former undoubtedly represents the sinus surroundiu^ th.e
loop of the alimentary caaial in the younj^ Phoronis, \\hile the
latter, 1 believe, represents the branches of the efferent ves-
sel v/hich become part of ti:e recipient vessel of the adult.
Masterman says that these branches open into the uorsal clood

(93)
vessel but such is not the case in the completely raetarro rfhosea
Ac tirio tro cha.,

'From a corripa.risor. of Llastennai:' s description of the vascu-
lar systeiri of the Actinotrocha and Ikeda's and my own descrip-
tion 0.^ the same be-f'ore ajia after metamorphosis, it is seen at
once that this systea develops more precociously in the form
that Kastermaii studied. This conaition, togetiier with the
facts that the lumen of the blooa vessels are parts of spaces
between the Y/all of thp -^vt and its mesodenrial liixiiii^ and that
the mesodemal linin;- of the alimentary caiial fits loosely viiile
the blood system is developing, gives additional \vei(-ht to J/Tas-
ternan's statement that the dorsal vessel opens into the so-
colled "suoneural sinus". Kov/ever, in the Actino trochae that
I i-ave exarfiinea such a connection does not exist and, as stated
above, a "sufcneural sinus" or cavity caused by a lacK of conti-
guity betv/een the mesodermal wall of the preoral lobe ana tnat
of the collar cavity is not present.

{&4)

Tne_ ^ault Pi:cai:i-s Archi tec ta.

Piioronis .-..rctii tecta was ciisccve'^ea by Andrews (1) in June
1L&5 at Beaufort, 1. C. anu no aesc-ibed it as a luew specied,
givin., it tne specific uaiue "archi tecta" on accouiit, no acnbt,
of itd bujluing a beautiful, atrai^iht tube. He finds that the
tubes are made up of a clear, firm, chi tin-like membrane coverea
with small clear grains of sand and he thinks tl;at these <_,rains
are selected by the animal. 1 have found that specimens col-
lected from different localities in Beaufort Harbor vary con-
siderably in regard to the character of the sand grains ana
quite often small fragments of dark shells are found mixed in
with the latter. Occasionally tv;o tuLea occur ce-oentea togeth-
er but this conaitioi. is rare for tney am usually iaolatea ana
imbeaaed pe rj. endiculariy in the sand. Wlien the specimens are
brou^..L into tne laboratory ana put into aquaria v^ith sand ana
wr.ter, tney usually crav/l out of their tubes ana be^in to -f^orm
new ones. Lon^^cnampo (12) has lately pointea out that the tube
is fbrmea by a secretion from the posterior ona o- ti;e anim.l

'^u not from tne anterior ena as Cori has saia. This 1 fina
to be the case for P. ..rchitecta.

Above it is statea that the tubes are straignt but wt.ere
new tubes are fbrmea in the aquaria, they are al.-ays twistea to
a considerable ex^nt and tney are attaci.ed fir.ly to the bottom

tube
t have a firm substratum tc which to cement its^ovit it is aeen

(90)
of the jar. In its natural habitat, Phoronia architecta aoea
not

fro.T: the above observation tiiat wi.on a solia surface presents it-
self, the tube may take on tiie condition fcuna in some cf the
other species of Phoronis v;riicii are attachea to rocks ana shells,

Phoronis architecta lives at about lov: v/ater i.-..*-a vii "nc
sc>,na b^wo^-uo h-'cn u.rr very numccus in Beaufort harbor and, as
_ rule, the individuals occur in patches. Three or four hun-
drea speciriiens are often found within a radius 0+"" four cf five
feet, but one is -very apt to find isolated specimens while dig-
gin^: in the sand anyv/he-n in the harbor.

Only rarely have 1 fouiiO tr.o tubes projectin.^ above the sur-
fS-ce oj.' t;.e oc.na o^a Aiidrews (1) has describea, and in these ca-
ses, the condition was aue to Disturbances o "^' the surface of the
sand, such as hollov/s maae by Callinectes. Usually the upper
end of ti.e tube is r*- .. -^ ^ . 5 c.u. belo\7 tx.e our fac^ cf the sand.

The average length of these tubes is 1? cm. and th3 average
width, a little over 1 rrcm. The adult when rem v-a ^-c m ito tube
is c^bout 1 mai. in aiameter in thie posterior one-tiiira ^^nd slij.ht-
ly les? in the anterior two-thirds. ("P'iL.ol) Tne length of
specimens taken out of the tubes varies with the auiount of con-
traction from 20 to 26 rm>. , v.-nich figures are consiaerably lower
. an the length given by Ajidrews (about 50.:^.). Tx.r. specimens

(96)
v/hich Mdrev/s describca mv^t have been c onaiaorably more extena-
ed tn^M aiiy 1 have kiliea. When the aiiimal io in .its natural
habitat aiici uuais turbed, however, it ii. capable; of ^reut exten-
sion; stretchin<_i ti:^ whole lonj^th of the tube and even consid-
erably farther .so that ito lophophoral end may project above ti.e
surface of tne sand ana reach for some covisiderablo distance
alonr, its surface, 1 nave not been ablo lo preserve specimens
in their extendea conaition and 1 find that they usually con-
tract to -''rom kO to 25 irai, in len^jth.

The anterior tv;o-tniras or tne li vin^^ specimen has a flesn

color, v/rxile ti:e posterior oiie-third is dark yellowish rea and

to the fact that
::u.ie opaque which is due^ .he ^^onads and blooa caeca ,aro sit-

uac-eo. in t hj .i re^;ion. In preserved specimens, the body v/all is
annulatea (l^i,,.61) but such is not tne case pro bau.- in the -ully
extended inaividual.

The crown of tentacles is .iuite simple comparea to the
crown 0^ tentacles in P. Australia, P. Eusxii and P. Pacifica. '
A cros. section shows that it i. crescentric ana that the e.as
are not spirally coiaea. ( Fi^^a . 62-63- 64)

Anarewo (1) has ^iven us a description of the principal
POi.ts in the anatomy o- Phoronis arcnitecta wnicn n. has un-
^oubtealy maae ,.ief because of the rese..lance to t .e anatomy
0^ Phoronis Australia as aescribea by Eenham (.). i, ,,,,,^,

(97)
1 fiiio that rro' observations aj^ree with these o^ Aiidre-.vs tut
there are a fev: points wnivAi it seems to ine wortn while ai scus-
B i ng .

Lo J ho j: ho r al 0 r .^ an s . _

These peculiar organs ("Fig. 62) have been observea in sev-
eral aif*"erent opeties of Fhoronis ana althou^J- "^rnctiono for
them have been suggestea yet tie observations do not seem to
have extended over a lon^ enoiii.v'i period, in the aault life of
tiie v-onri to "/arrant a aefinite st ^t'^r.icnr ^t. to tnoi r ■■'■'i_i. ti on.

The lophophoral or^^ans (Fig. 62) lie one on each side cf
the median line within the concavity of the lophophore. They
are outgrowths from tiie base of tiie inner ro v.' of tentacios ana
in seme species, at least, are quite conspicuous organs, but
they do not arise until the Fnoronis has readied its aault siiie.
Organs locatea in the above region have been describea for
eight species but the si^e and shape do not aeern to be the saine
in all. V/hetlier tl,ese differences are specific or v/noths'- the
observations have been made at different perioas Jn the aault
lif-, it is hard to say. lophopncral organs, like ti:ose pres-
ent in Phoronis architecta ar- fbund in P. To .mmopMla, P. P..-
cifica, P. Mfille.i .na, I suppose, i. some otuer specie, also.
It seems, i,o.ever, probable fVom the aescripticn of the anatomy
Of P. Pus.ii an, P. Australia t.at in these spece., .he loph-

(96)

ophoral organs are mucii less hi,:hly aeveloi:ea thcU'i in the smaller
species 7;ith fewer coils ivi ti.e lopho-phoral crovai. 1 have ex-
aminea several specimeus of P. Australia v.l tr. ana vathout: fc-eu-
ital prodiict^i b- " '- .1 ix ^^-^ h^v^ I seen or^^ans su.ch as are pred-
ent in P. architecta.

Various functions have 1 3 on ^oo^t;,n. ... ^c the lopJiophorai
;: f-{.,c;no , M'lnt^ sh (j.4) vjo rkiiii, ui th P. EnsKii considers that they
are sensory in fxuiction, '.vhile Masterman (16) , who has studied
the same species, says that ti;ey are glandular ai^a that they
i;:ive rise to mucus which serves to hola the embryos together in
masseti. In other worad, n" uonsider^ ti.ein to be "viriDviJ uicvry
reproductive organs". Eenham (2) v/ho workea Oix P. Australis
and Con (4) who inves tie;aCed V. psamrnophila both r,ive these
organs a j-landular function; v/hile Andrews (1) thinks that in
P. architecta they are used in buildin^, tr.e tubes. H.B. Torrev
{k.2) has made tne interedtini; cbsorvaticn that in souie specimens
0^" P. Pacific, the l.,n.,.h.-^x ^y^,xuS ^re like those in P. Aus-
tralia "mile in others, they are like those ii. p. arch.i tectc..
It is probable that in part of ti^e specimens ■.vhicr. Torrey ex-
amined, the lophophcral organs were iio t full ^ro-.M., while in tlie
rest, they had reachea their full development.

My observations led me to believe that Anarews's supposi-
tion concerning tne tube builain^ n^nctioa 0- tne lophophoral

(99)
orcaua is incorrect. liiOiviunals v/ithout luti lo^hori^o ral or-
gans L-uilo nev; tubes coverea wi tii sana Li"aius just as ao those
viti. the organs ana yc vm^. specimens of Pliorox.is archi tecta,u'mch
are in possession o^' tubes, never have lophoi-ho -^al organs.
These two facts prove quite couclnsively that t<.e lophophoral
organs o^'Phoronis architects are not used Tor tube building,

i/Iasterman's view tnat the lophophoral orga.. ol P. Euskii
are gla.naular' and that tney furnisi. mucus to hola t];o eg^s and
'''rnbryos in raasses cannot te appliea to P. arcnitecta, I'o r in
this species the eggs ana embryos are not held in njasses,

I have exaclnea specimens o "^ Ph.oronio architecta duriu^ al-
most every month in the year in oraer to discover v-ihezher or not
th.ere is any relation between the lopliopnoral organs and the
breeaing season. Durin^- the months of June, July, August, Sep-
tember and October exa/rdnation of njany specimens o -f^ Pnoronis
architecta shows that more thai, one half are with lophophoral
organs; i. e. , v.dth the "carpel like organs" and the "spi:erical
sense lobes" ( Ar:dre-A's) . Exai.d nation of specimens taken durir.g
.'.ese months s hov.'s that some contain ovaries and ej_;.b while
others do not and that :liat all contain spermatozoa in the body
cavitybut that only those without ovaries, contain teates. Oc-
casio..ally an egg floating freely in the body cavity is ft) una in
specimens with testes. These facts, 1 fina, are correlated v;iti

(100)
the presence or the abseuce of the lophor-horal or^ai.s, for these
orcaiis are pro^ei.t in spficin.ens -.vi th testea anci without ovaries
and abser.t in .-opecimei.a ■.vi tn cvari'io and witiiout testes.

Duriiiij the latter part of Decemuer ana the first j,art of
January, 1 exaadnea speciiiiens of F. arciiitecta, soiiie of

v/hich. v/ere coliectea in Beaufort Harbor at that tine anil some
o-f" which had been kept alive in the laboratory of Johns Hopkins
University since the sumnier months.

Many of these speciTicna (50 or 40) were examined by crush-
ing the posterior eiid ana also by cuttin;^ sections, cnt with one
exception, all of these individuals were found to be v;ithout
ovaries anc. testes. In tie c^ise of the eyception, u fev ova-
rian eg^s were present but the ovaries v/ere still very younj^.
The blooa caeca at this time are surrounded by a great abunaaiice
of the peculiar peritoneal tissue v;hich later gives ri oe to th.e
reproductive organs. Lophophoral organs v/ere abse-t both in

specimens collected at Eeaufoi^t aurin;^ tne first part o"'' January

in
ana^specimens coliectea auring the summer and kept in tr^e labo-
ratory.

During the rioi.ths of February, March and April, tne opec-
Jinens iri the a.iuaria at Johns Hopkii.s University were examinea
:uite frequently but until March or April, there was no si^n of
lophophora] organs. Then they began gradually to a-v^lc: in

(101)
soirie srecimeiiS until by the first of May, they were -ull 3ik:e.
At tius time, another lot of live material was receivea from
Eeaufort V7hich affordeci some ver;/ interea tin-, obBervations. The
nuTTiber o^ ir-aividuals v/i th aria -^-ithout lophophoral o rgarib were
in about the same ratio as aurin,.; the oUirLTier months. At this
time, in specimens with lojhophoral or^rans, the testes are presenb
tid, ti:e ovaries are not, Y/i:ile specimens v/i thou t loi:hothoral
orgaiiS possess ovaries arxCi contain ovariaii ej-^s. Quite often,
specimens with lophophoral orf.ans have lart-'e bunches of sperma-
toiioa -^loatinc; freely in the boay cavity, and in some cases,
these occur inside the nephridia. (slide V/l' ) In one individual,
1 have found a large bunch of spermatozoa lodjjed iii the end of
the lophoral or/ran*s pocket-lifc: cavity.

Judginj: from the obgervativns tl-iat 1 have made, it seems
to me that the relation of the lophophoral organs to the breeding
season is as follows:- Some adults are giving rise to eggs through-
out the irionths of M.ay, June, July, August, September and October,
Hone of ti:e individuals arising from these eggs become sexually
mature until I.^arch o^ April of the next year. Those which are
the oldest; i. e. , those born in the early months of the year
I before, develop testes ana lophophoral organs in j.iarch or April.
Then they lose their lophopnoral organs, ihe testes disappear and
ovaries begin to aevelop about the first o ^' May. Y/hile this

.\ jxviio t-iiiX-Je

(lOi:)

is £0iu-: on, iudivi duals whicl: wero bom later in U.e aumner of

tne vpar- bn-f"o re, L-e,,in to aevelop testes ana lo f hopho rul organs

aji'i t^^us we have iiiaiviuuals with lopt'Opno ral orj^ans and testes

the
occnrrinii; at the same tirac o f^ year as imividuals without loph-

ophoral organs sua with ovaries.

V/hile 1 have liO absolute proof, 1 thinx tnat the upper part,
at least, of tne lophopnoral or^raixS, +'unctions as a kind of
seirdnal rec^'ptacle. 1 am lea to this conclusion by these
■f'actst first, tnat tiie oru,ans appear only when tv.e testes are
present; second., tliat 1 have seen lar^re bunci.es of sp ermatczoa
in the body cavity, in the nephriaia ana in the cavity of the
lophophorsl or,,an3; ana third, that ti.ere are ciliatea ^.rocves
leaaint;:: froin the nephriaial pores to the cavities o^ tj.e loph-
0 p i ic r al 0 r £:. ans .

— Vascular Sxstem:^__ Nearly all o^ the early investigators
of the anatoirry of Phoronis recognize the existence of an effer-
ent and afferent vessel ;vnien are in connection witn vessels run-
ninij up into the tentacles.

Calawoll's (3) aescription, altnourh brie-, is coinplete arzd
differs verj little -ro:a later ones.

Cori's (4) account seems to be whrnt n« <, ^ .

^^ ae cib>^ut the saiue as Calci.vel 1 '3 ;

however, he recognises one rin^ vesse;

t3cribes in raore detail the relati
a els aiid the ring: vessel.

^e^ instead of two and de-
ion between tl:e tentacular ves-

(lOo)

In Pnororiis Australia, Benhaxn (2) finas the circulatory sys-
tem much the sajiie as Caldwell does in the form that he worked on.
Practically the only point of difference is that he describf^s
the tentacular vessels as dividin., into two branches, one open-
in^j into t!ie distributing vessel (inner) and the other, into the
recipient vessel (outer).

Andrews (1) finds that the vascular system of P. architecta,
as far as he has dete'-mined, ip 3i^-e tl:at c t' P. Australia '.vhile
Ikeda (9) days ti.at Be.x..a-. ' .-. :..c .ri; tio.. holas 1^00 d for P. Ijimai
and P. hii:.r"<^crepia,

A transverse section thnouj. the lo^hotliOral crow:, or P.
architecta (l^ig.65) shov/a tnat tne cavity of each tentacle con-
tains a blood vessel \;hjch is attached to the inner surface of
the :"all.

At the base of the tentacle^, a cress secHon sh.^s that
tne.e are t.o blocu v-^..^.. runnin, parallel to one another through
:nost 0- their course arouna the cavity 0- the lophophore. (^gs.
65 to 71) These vessels are distinct although closely appliea
to one another, thus differing from what Cori finds in P. psam-
-Phila. The outer ves.el and inner vessel (Fi,3.6d-.6) are,

distributing" vessels which
ros-6 section throu;h

respectively, the "recipient" ar:

Eenham aeuc rices. in f-i ,- f-- .^ ■

in .1^. bw IS sricwn a c

tne base o

-o tentacle;

Th no ujiout most 0 ^ t

he sectioii the

(104)

tentacular v^^ysels opeu into tne outer or recitieut vessel but
at one end the tentacular vessels o?en into tr.e irmer or distrib-
uting; vessel. Thid section, together \n th sections anterior
and posterior to it, sLov.- coi.'cliia ivoly tliat the te..tacular vessel
has two separate openings, one into the distributing vessel, the
other iLto the recipient vessel and that the distributing and
recipient vessels are completely separate. A longi tuainal sec-
tion tn'-ou^^h the anterior end of Phoronis architecta shov/s con-
clusively that the tentacular vessel divides into tv;o branches,
one opeiiiii^ iiito the recipient vessel and the cths'^, into tliC
distributing^ vessel.

A little iTiO re posteriorly, the rint;-liKe dist ri butinj; ves-
sel opens into a median lon£;ituainal vessel I'yin^ between the
Gesopha*_^us aiid r^ectum but close to the \7all of tlie fo'~mer, ('Pi.js,
67-6L) This vessel, whicii is tr.c afferent vessel, pierces the
transversa yeptum ("Pi,j;.69) ana rnxin posteriori:,' (within t]-:e rec-
tal or posterior chasJjer) betv/een the tro iirma 0 ■*" the alimentary
canal. At the point \'{lr ere the vessel passes throuj,]; the septum,
mere is a thick layer of muscle ^ibers surrounding the -^onner
v:hich undoubtedly has tne power of shutting, off the blood supply
to r, Kf? tentacles axio -mich nia.7 be very necessary tp prevent the
animal fro 1:1 deeding, to death v/hen the lophopnoral crovm is cast
away. C^igs.ee to 71)

(105)

T..P t'vo siaes of the rint,-lii.e recipient vesdel ao not pasa
iiito a siiij.le vessel wiiile u.ey are witi.in the sujradC3ttal cavity
(■Pigs. 67 to 71) but after tney have piercea ihe trfujoveroo dop-
tvui, the rigl-it side of ti;e riu^, is aeeu tc j^^as^j diat^Oiially across
the oesophagus ana to meet the left side of the riijii. CF'itS. 7i3
to 7^) 'From this point, the tv.c become oi.o vesdel, tr.e efferent
vessel, v;hich runs posteriorly within the left body cavity.

In the posterior part of the body, v.here the a.limentary ca-
nal nai^'es a loop, the efferent aziO. affo'^ent vessels are contin-
uous and open into a sinus around the stomach,

Alon;^ most of the course of the efferent vessel, blood caeca
are civen o f^^" and a large bunch also arises fruiu ti:e sinns.

ITervous System:- We have found that the nervous system of the
Actinotrocha is more highly developed in some species than in
others ar.d that it is subepidermal in character. In the differ-
ent species of the adult, we also find that there is considerable
difference in the degree of development of the nervous system
and that it is largely subepidermal.

Caldwell ^5^ was ti.o first to give a gooa descriptor, of
ti:e nervous system althou^. Kowalevsicy (11) recognised the ex-
istence Of a lateral nerve ana ganglion. Caldwell f.und the

Of two ciliat.d Pits consisting of nerve cells, ga.^lion and

(106)

nerve fibers. The descriptioi: is brief so 1 am "not able
0 r iio t
to say whether the eani^lion that he speaks o^ represents the gan-
glion that Kov/alevsky (11) and Cori (4) ciescribe.

Benham (2) finds no gan£:lion in P. Australis but describes
two small areas wl:ich, it seems probable, are the same as Cald-
well's "ciliated pits". He is the first to recognize the ex-
istence of a lateral nsrve on the rij^ht side as v;ell as on the
left, and he finds a nerve ring with a nerve to each tentacle
arising from it.

Cori (4) describes a definite gaiiglioii, a lateral nerve
on the left side only nd tentacular nerves. Ke is the first
and only investigator who has published anything on the distrib-
ution o^ the nervous tissue in the lophophoral orga^i,

Andrews (1), Torrey (22) and Ikeda (9) have given very
brief descriptions of the nervous system but the t vvo former rec-
ognize the existence of a short lateral nerve on the right side
as well as a long one on the left side, v/hilo the latter speaks
of a so-called brain ganglion and nerve ring.

The account which Andrews gives of the nervous system of
P. architecta is ver-j brief since his paper only deals v/ith the
description of a new species. Ke only speaks o^ the lateral
nerve and makes no mention of a brain ganglion, ring nerve, ten-
tacular nerves ox nerves to the lophophoral organ.

(10 7 )

In ge-neral, my obscrvatious O'n the lateral 'nerve of P. arch-
itecta agree with those of Aiidrews and Torrey. The lateral
nerve o^ the left side is quite conspicuous and extends from the
anterior end to a toi^it about one- third from the posterior end
of the animal. It runs along the lateral body wall until it is
almost in the region of the transverse septum, chen it gradually
passes obliquely upward in close proximity to the left nephridial
canal and finally is seen imbedded in the ectoderm at the side
of the anal papilla. f^rom this point it passes around the base
of the anal papilla between the anus and the mouth, and then it
begins to take the sairio course close to the nephridial tube on
the right side as i« did on the left side but it soon grows much
smaller in di&jneter ana finally disappears. (Figs. 76 to 67)
A longitudinal section passing through the mouth and anus sliows
the relation which the nerve cord bears to the ganglion and nerve
ring. (Fig. 84) Cori (4) figures such a section thj-ough P. psara-
nophila but he seems to have overlooked the nerve cord or axis
cylinder in this region. It is closely associated wit}: the cells
of the ganglion and lies Just a little below the latter. In an
oral direction from the ganglion is seen a section through the
nerve ring.

If a cross section (Fig. 65) is taken through the ganglion
so as to cut longitudinally through the nerve cord and if the

CliiiJ'

(106)
sectiori is stained deeply with iron haematoxylin and eosin, it
will show plainly that there is no cavity in the cord but that
it is made up o^ a mass of fibers surrounded by a nucleated
sheath. Caldwell (5) considers the structure to be a hollow
nerve cord; Eenham (2) says that it has a semi-fluid contents and
chat he has been unable to make out any punctated nerve substance:
and Cori (4) states that it is an axis cylinder.

1 have endeavored to find some coiinection between ti~.e cord
and the ganjrlion but have liOt been very successful. In the re-
gion 0-^ ti.e ganglion: i. e, , between the mouth and the anus, the
sheath o -^ the nervo cord does not seem to differ in thiclaioss or
character from the same structr,re in other parts. The cells of

th.e ganglion, however, sena out processes wiiicli in sections are

the
frequently seen applied to^ sheath but 1 6'ould make out no connec-
tion between the fibers of t.i ^ n-rve ring and those of the cord.

Kowalevsky (11), Cori (4) and Torrey (2ii) have all found
the nerve ganglion, while Renhain (2) aonies its existence in P.
Australis. It undoubtedly exists in P. architecta, is situated
at the base o^ the anal papilla between the anus ana the inouth,
aJTid lies above the nerve cord between the anal papilla and the
nerve rinj:^. ("Pig, 64)

The ganglion consists of nerve fibers aiid nerve cells ana
the latter have at leo.st two processes. m.ila ^ is a defmiit

(109)
structure back o^ the anal papilla, on the siaes, it dimiriishea
in size until its cella become indistinguishable from those of
the nerve rin.-. In fact, all of the ectoderm fortiiin.: the sides of
the re eve between the anal papilla and the base of the lopho-
phore i^ rich in nerve fibers and cells.

The nerve rinjj fcllov/s tre base of tlie lophophore on the
outer side throue,hout its extent and in the inner part o-f" the
horse-shoe, it is quite rich m nerve cells whose processes can
be seen penetrating into the mass of fibers, (Figs. 67 to 74)
This ring represents the collar nerve ring of the Actinot rocha.

There is a definite tract of nervous tissue running up the
inner side of the tentacle but 1 am not prepared to say that it
is a nerve naming from the ring although it is nervous tissue
v.hich is undoubcedly continuous v.'ith that of the nervu ring,

Cori (4) has carenUly studied the anatomy of the lop'^o-

phoral orgajn of P. psammophila and 1 have nothing to aad to his

or no t
description at present, I am also unprepared to say whether}^ the

second la:,er of the lophophoral organ consists of nerve cells,

As he has described, they have lon^, prolongations ';^.ich

extend from the cells of the inner layer to the outer and these

processes f o m a rather marked layer just below tl;e epidermis on

the outer surface o^ the organ. At the base o- t^.e lopho,horal

orgaii, these prolongations seem to be intimately associatea with

(110)

uerve fibers wnich car. be tr^.«:I to tl-.e .aorve riut,.

Throughout the body wall of the trunk therf; is a subepider-
Hial layer of riorvou.s tissue.

ITephridia;- 1 have i:othii':, v.ew to adci concerning the adult
nephriaia but my observations on ^. architecta confirm those of
Eenham (2) for P. Australis. The nephridial cax:als lie iucedded
in the ectcder/rial wall in the region of the rectum. They each
oten to the exterior through a yore at the side of the anal pa-
pilla. "P'ollov/iiig the canal from tha nephridial pore, we see
that it passes downward; i, e., posteriorly, f o r a sliort distance
and then bends upon itself running upward parallel to tiie descend-
ing arm, A short distance above the bend, it opens by one fun-
nel into the lateral bo ay cavity (■p'ig.72) and by aiiOther, into
the rectal body cavity. ("^ig.yo)

Reproductive Organs;- Ikeda's recent paper (10) on the re-
prodi;ctive organs of Phoronis gives a good account of the anatomy
aiid development so I shall not enter into a description of them.
I am able to confirm Andrews's observations that ti.e male organs
develop at a different time from those of the female.

Ciliated Ridge o/^ the Alimentary Canal;- Andrews has de-
scribed a ridge running along the inner wall of the oral branch
of the alimentary canal. C^ig.Sl) H. P. Torrey has found the
same structure in P. Pacifica aiid 1 can confirm Aiidrews's obser-

(Ill)

vatioi. i-or P. architecta. This ridge aoe?? .,ot seen, to l-.avc
any rudimeiit in the Ac ti nor, roc ha and it is not present just
after metairiorphosis.

_ Suinraa.ry_>_

The male and feruale reproductive organs do not develop at
the same tirrie in P. architecta aiid the inaications are that it
is a protandrous animal,

i^'ertilization in external and the eggs are not held in loph-
ophoral masses by tne tentacles.

Segmentation is holoblastic and equal but cleavage does not
occur sinultaneously in all the blastomeres. During the divi-
sion of the four-cell stage into the elgtit-cell stage, the upper
four blastomeres rotate in tne direction of the hands of a watch.
The sixteen-cell stage arises from the eight- cell stage by a
meridional division o^ each blasLomere,

The blastopore is eccentric from tiie beginning of gastru-
lation and the gaiiglion of the Actinotrocha makes its appearance
at thds time. As developmenc proceeds, the blastopore gradu-
ally closes up from Ihe posterior end toward the anterior end
of the larva until finally it becomes a transverse slit.

The "primitive streak" of Caldv/ell does not seem to be pres-
ent in the larva of P. architecta.

(11-)

The "nephridial pit" is of ectodermal orxcin.

The mesoderm arises from the endoderm. Archeiiteri c diver-
ticula are not present in the larva of P. architecta but there is
a sac-like formation of mesoderm cells in the anterior end which
forns t!:e lining of the preoral lobe and wi:ich gives rise to a
mesentery between the lobe and collar cavities.

The linii'c of the collar cavity does not arise froiii a mes-
odermal sac. It is formed by isolated mesoderm cells which ar-
range themselves on the somatic wall leaving the splanctoic wall
practically without any lining.

In the larva of P. architecta, the mesodermal lining of the
trunk cavity is complete, covering both the somatic and splanch-
nic walls arid it seems probable that it arises from cells forming
the base of the nephridial diverticula. There is a mesentery
between the cavities of the trunk and collar,

A stomodaeum saio. proctodaeum aru not present. The blasto-
pore becomes the mouth, the anus arises quite late in the early
life of the embryo and the rectum is for/red as an outgrowth of
the blind end of the archenteron.

The nephridial canals, at least;, have their origin in a sin-
[ gle median pit which soon branches into two intercellular tubes.

I have noL found any evidence that the excretory cells of the ne-
^ phridia are forxred from free mesoderm cells attaching themselves

(115)

to the blind ena of tl:e nephriciial caiialy.

The "neuropore" and "subneural t^ldsad" which Mastenrian has
aescribea cio uot exist in the Actinot rocnae that I have exaMned
althout^i imperfeetl;/- pregerved specimens show unusual struc lures
which miglrit be taken for these organs,

Masterman's "subneural sinus" is not present either al-
though there is a space below the gant-,lion whicl: is free from
mesodennal strands. The "atrial grooves" which Mastenaan says
exist are present in tiie larvae 1 have studied but 1 cai-inot con-
sider tl^at they have ti:e significance ti.at he assigns- to them.

are
Occasionally grooves ^ f'ound which migi.t be comparable to Master-
man's "oral grooves" but they are duo to imperfect fixation. The
stomach diverticula exist in one species that 1 nave examined
but they do net impress me as being of notochordal nature as Roule
and Mastennan have claimed.

There is a subepidermal layer of nervous tissue throughout
the body. Extending, anteriorly from the ganglion, which is sit-
uated on the median dorsal surface of the hood, are three longi-
tidunal nerves which Anally become continuous with a nervous
ring running around the edge of the hood. l^rom the posterior
side of the ganglion two parallel tracts of nerve fibers issue
and pas. posteriorly alon, the dorsal collar wall until they
reach the circle o+' tentacles -^.ere most of tnem follow the line

(114)
of insertion of the collar trunk mesentery and si ve rise to a
collar nerve ring. The nerve fibers from the edge of Che pre-
oral hood do not pass up to the gaiiglion from the point of at-
tachment 0 "f the hood on to the collar wall as Masterrrian has de-
scribed^l^ut triey make a sharp turn running posteriorly arid
obliquely alon^ the lateral and ventral wall of the collar, where
t' le y form two definite nerve tracts which become lost in the
region of the collar nerve ring. While there may be nerve fi-
bers passing from the gajjglion out in all direct ioiiS over the
sur-^ace of the hood, 1 have not beeii a.ble to make ti:emout, nor
do 1 find any definite nervous tract ninning along the dorsal
or ventral v/all of tlie trunk segment.

There is one pair of retractor muscles extending from the
region of the ganglion to the collar walls in the region o"f* t,he
first and second pairs of tentacles ar^ beside these in one Ac-
tinotrocha that I have examined, there is another pair extending
from the sides of the gaiiglion to the veritral wall o -^ the hood.
In this latter Actinotrocha there is an extensive layer of mus-
cle fibers in the wall o^ the hood and also a ring of fibers
around the edge of the latter, A pair of longitudinal muscle
tracts extend from the region of the ganglion alon,: the dorsal
wall of the Actinotrocha to the perianal ring ana there is a sim-
ilar pair of rrd,cts extending along the ventral wall of the col-

(115)
lar and trunk. A rim, of muscle fibers run r-arallel with the
rin£ nerve between the collar and trunk sei..,ments, Eeside
these muscle tracts there is a layer of circular fibers in the
wall of the collar and trunk lyin^ between the longitudinal fi-
bers and the ectoderm. There is also a covj-intj of ruuscle
cells on the ventral pouch, aiid on the wall of the dorsal blood
vessel.

The nephridia have much the saiiie structure as
as
tJaose of Amphioxus described by Goodrich, In one of the

Actinotrochae from Beaufort Harbor, the nephridial canal branch-
es but in the other, it does not, ITephridial funnels do not
exist bT't t,.,,e ends of the canals open into tubular cells and
the lumen of each cell contains a flagellum. The nepnridial
canals open to the exterior at the sides of the orifice of the
ventral pouch. The nephridia which Masterman describes for
the preoral hood ana trunk are not present in any Actinotrochae
that I have exaimined.

The blood vessels of the Actinotrocha are formed from the
splanchnic mesoaennal linin^: and tl:ey enclose part of the blas-
tocoel. There is a dorsal blooa vessel opening (?) anteriorly
into the space between the storriach wall and the splanchnic lin-
ing;. At the posterior end of the stomach where the dorsal
vessel ends, th^ere are caeeal vessels formed as eva^jinations

(116)
of the mesodermal lininj-: of the stomach. The aorsal vessel be-
comes the afferent vessel of the adult while the efferent vessel
does not arise until just after metamorphosis, Tne collar cav-
ity,vvhicri is a part o ■f' tne blasto coel, becomes the ring vessels
and tentacular vessels of the adult. There is no connection
between the dorsal blood vessel and Masterman's "subneural sinus'

The blood corpuscles arise from the somatic mesodenrial lin-
ing, of the ventro-lateral collar wall just in front of the sep-
tum. They make their ap-^earance as tv/o masses of cells bilat-
erally placed, one on each side of the median ventral line and
as ihe-j develop, they migrate across the collar cavity and be-
come applied to the naked walls of the stomach.

The rudiment of the supraseptal or collar cavity of the
adult makes its appearance in about the same rej^ion as do the
blood corpuscles but a little later in the life history of the
Actinotrocha,

During metamorphosis, the follomng organs are lost: the
preoral lobe, the gai^glion and the larval tentacles. The ec-
todermal wall o^ the collar cavity, the stomach diverticula, the
digestive areas and the perianal ciliated ring are not destroyed
but they lose their identity. The subepidermal nervous layer
of the trunk aiid ventral pouch becomes part o<^ the same tissue
in the adult but- the larger part of this tissue, as well as the

(117)
lateral nerve, the gauglion and the nerves to tlie lophophoral
organs are new formations.

All of the nervous struct ureXof the collar and trunk are
lost during sietamorphosis except the collar trunk nerve ring,
which persists as the nerve ring of the adult.

The ventral mesentery becomes the oesophageal and rectal
mesenteries of the adult aiid the cavities of the trunk and ven-
tral pouch are transfoniied into the iafraseptal cavity.

At least the greater part of the nephridia is lost during
me t aiiio rpho s i s ,

The lophophoral organs arise late in the adult life and
are present oixly in iiidividuals v/hich are v/ith testes and with-
out ovaries. They probably serve as seminal receptacles.

The vascul9.r system of the adult consists 0"^* an efferent
sxjd afferent vessel which are continuous posteriorly by means of
a sinus around the loop of the alimentary canal; q-^ caecal ves-
sels as outgrowths from the afferent vessel and the blooa sinus;
of a distributing and recipient ring vessel, the former opening
into the ef-^erent vessel and th.e latter, into the afferent ves-
sel; and of tentacular vessels, eacl: of which divides into two
short branches, one opening into the distributing vessel and
the other, into the recipient vessel.

There is a ciliated ridge extending alon^ part of the inner

(116)

wall of ihe alimentary canal.

The nervous system of the adult is to a great extent sub-
epidermal. There is a nerve with a nucleated sheath extendini^
alon^^ tl:c left side of the animal. Anteriorly it bends arouna
the anal papilla and continues as a short nerve on the ri^^ht
side. There is a gaii-^lion between the mouth and anus. A
nerve ring extends around the base of the lophophore and it
gives off nerves to the lophophoral organs. There is ner-
vous tissue in the walls o"*^ the tentacles.

The excretory organs are pairea and each noi-hriaium con-
sists of a tube bent upon itself. One end opens to the exter-
ior while the other is continued into two funijels, one corrimun-
icating with the rectal and the other, with the lateral body
cavi ty.

The reproductive organs arise from the lining of the caecal
blood vessels sjrjd the male organs develop at a different time
from those of the female.

EiOirraphical Sketch.
Rhc'inart Parker Cowles v/as born in V/ashington, Iowa in
1672. Kis father's nanie is Oscar Parker Cowles ana his
mother's n^aiden name was Viola Parker. Ko obtained his
corrmion sei:ool education in I'filwaukee, ?/isconsin ana after
that went into business for several years. He was in tl^.e
employ of ti:e Milwaukee Gas Company for one year and also
with the Remington Typewriter Company for the same length
of time. His Bachelor's Degree was received from Leland
Stanford University in 1699 at Palo Alto, California,
In 1900 he entered Johns Hopkins University for graduate
v.'ork. During 1901 and 1902 was a University Fellow and
in 1902 received the Adairi T. Bruce fellowship which he held
for two years. He has publish.ed a paper in the Biological
Eulletiii on the Larva of Polygordius.

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