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INVERTEBRATE 
ZOOLOGY 


DREW 


Fifth  Edition 
Revised 


MARINE  BIOLOGICAL  LABORATORY. 


Received  August    8,    1938 

Accession  No.     49228 

Given  by       IV   B»    Saunders    Co. 


Place, 


Philadelphia*     Pa« 


***  fio  book  op  pamphlet    is  to  be  removed   from  the  Lab- 
oratory taithout  the  permission  of  the  Trustees. 


=  D 


A  LABORATORY  MANUAL  OF 


INVERTEBRATE 
ZOOLOGY 


BY 

GILMAN  A.  DREW,  PH.D. 

Late  Assistant  Director  of  the  Marine  Biological 
Laboratory,  Woods  Hole,  Massachusetts 

Revised  by 
JAMES  A.  DAWSON,  Ph.D. 

Associate  Professor  of  Biology,  The  College  of  the 
City  of  New  York 

AND 

LEONARD  P.  SAYLES,  Ph.D. 

Assistant  Professor  of  Biology,  The  College  of  the 
City  of  New  York 


FIFTH  EDITION,  RESET  —,  ._  jsif 


Ms* 

PHILADELPHIA  AND  LONDON 

W.   B.  SAUNDERS  COMPANY 

1936 


Copyright,  1907,  1913,  1920,  and  1928,  by  W.  B.  Saunders  Company 


Copyright,  1936,  by  W.  B.  Saunders  Company 


All  Rights  Reserved 

This  book  is  protected  by  copyright.  No  part  of  it 
may  be  duplicated  or  reproduced  in  any  manner 
without  written  permission  from    the  publisher 


MADE  IN  U.  6.  A. 

PRE88  OF 
W.  B.  8AUN0ER8  COMPANY 
PHILADELPHIA 


REVISERS  OF  THE  FIFTH  EDITION  OF  DREW'S 
INVERTEBRATE  ZOOLOGY 


James  A.  Dawson,  A.B.,  M.A.,  Ph.D. 

Associate  Professor  of  Biology,  The  College  of  the  City  of  New  York. 

Instructor  in  Invertebrate  Zoology  Course,  Marine  Biological 

Laboratory,  1920-1925. 

Instructor  in  Charge  of  Invertebrate  Zoology  Course,  Marine  Biological 

Laboratory,  1926-1931. 

Leonard  P.  Sayles,  A.B.,  A.M.,  Ph.D. 

Assistant  Professor  of  Biology,  The  College  of  the  City  of  New  York. 

Instructor  in  Invertebrate  Zoology  Course,  Marine  Biological 

Laboratory,  1930- 


PREFACE  TO  THE  FIFTH  EDITION 


The  present  revision  of  this  Manual  has  been  made  by  the 
undersigned  for  the  purpose  of  modifying  and  enlarging  the 
fourth  edition.  Some  important  changes  in  classification  have 
been  made  and  the  instructions  for  the  study  of  certain 
commonly  used  animals  have  been  made  more  complete. 
Such  errors  as  had  not  been  eliminated  in  earlier  editions 
have,  it  is  hoped,  been  corrected.  The  glossary  has  been 
thoroughly  rewritten  and  enlarged. 

J.  A.  Dawson, 
L.  P.  Sayles. 

New  York  City,  N.  Y. 
March,  1936 


PREFACE 


This  manual  has  for  its  basis  a  set  of  laboratory  directions 
prepared  by  the  instructors  in  the  Zoology  Course  given  at  the 
Marine  Biological  Laboratory  at  Woods  Hole,  Massachusetts, 
for  the  use  of  students  in  that  course.  These  manifolded  out- 
lines were  first  used  in  1901.  Associated  with  me  in  the  prep- 
aration of  the  first  notes  were  Dr.  Robert  W.  Hall,  Dr.  James 
H.  McGregor,  Mr.  Robert  A.  Budington,  and  Dr.  Caswell  Grave. 
For  several  years  the  notes  were  modified  and  additions  were 
made  before  there  was  any  thought  of  publication.  During 
this  period  other  instructors  became  members  of  the  staff  and 
added  to  the  directions.  These  instructors  were  Dr.  Winterton 
C;  Curtis,  Dr.  D.  H.  Tennent,  Dr.  Otto  C.  Glaser,  Dr.  Grant 
Smith,  Dr.  John  H.  McClellen,  and  Dr.  Lorande  L.  Woodruff. 

Since  publication,  the  instructors  in  this  course  have  offered 
many  suggestions  and  criticisms  that  have  aided  greatly  in 
revisions.  I  am  especially  indebted  to  Dr.  Lorande  L.  Woodruff, 
who  has  given  much  attention  to  the  revision  of  the  Protozoa, 
and  to  Dr.  Winterton  C.  Curtis,  Dr.  Caswell  Grave,  and  Dr. 
W.  C.  Allee,  who  have  successively  been  in  charge  of  this  course. 

Probably  few  instructors  will  find  it  desirable  for  their  stu- 
dents to  follow  closely  all  that  is  given  in  this  manual,  but  it  has 
seemed  better  to  arrange  the  matter  in  a  logical  order,  and  in 
some  of  the  forms  to  call  attention  to  only  the  important  points 
of  anatomy  or  adaptation,  than  to  try  to  make  the  directions 
for  each  form  complete  in  themselves. 

Since  the  first  appearance  of  the  manual  in  book  form  there 
have  been  many  suggestions  that  directions  for  other  forms  be 
included,  or  that  more  complete  directions  be  given  for  some  of 
the  forms  treated.  These  suggestions  have  been  followed  in 
many    cases.     There   is,  however,  danger  that   students  will 

9 


10  PREFACE 

learn  only  to  follow  directions,  while  they  should  be  encouraged 
to  devise  their  own  methods  of  getting  at  the  facts.  For  the 
comparative  study  of  related  forms  complete  directions  are 
not  needed  and  should  not  be  given.  The  method  sometimes 
used,  evidently  the  favorite  method  of  Agassiz,  of  giving  a 
student  an  animal  without  directions  and  letting  him  work  out 
his  own  salvation,  is  the  true  research  method,  and  to  this  all 
who  continue  with  Zoology  must  come  in  time.  It  is,  of  course, 
laborious  and  time  consuming  and  not  adapted  to  course  work, 
but  there  is  danger  that  its  great  value  will  be  overlooked. 
It  is  so  much  easier  for  both  instructor  and  student  to  follow 
directions. 

The  type  method  of  laboratory  study  has  for  many  years 
been  the  prevailing  method,  but  care  needs  to  be  exercised  to 
keep  students  from  making  everything  conform  to  type,  and  in 
leading  them  to  see  the  wonderful  adaptations  that  fit  the  dif- 
ferent animals  for  their  particular  lives.  The  manual  is  not 
intended  to  lead  students  to  a  knowledge  of  comparative 
anatomy  alone,  but  to  an  appreciation  of  adaptation  as  well. 

There  has  been  no  attempt  to  make  the  literature  list  at 
all  complete,  but  it  seems  desirable  to  refer  students  to  some  of 
the  available  papers,  for  by  consulting  them  in  connection  with 
their  laboratory  work  they  become  acquainted  with  methods  of 
work  and  develop  the  spirit  of  research  that  is  the  beginning  of 
real  understanding. 

Certain  books  that  have  not  been  mentioned  under  the 
special  heads,  as  they  apply  to  practically  all  groups,  should 
be  used  freely  for  reference.  Among  these  may  be  mentioned 
Parker  and  Haswell,  Text-book  of  Zoology,  Macmillan;  Lan- 
kester,  A  Treatise  on  Zoology,  Black;  Harmer  and  Shipley, 
The  Cambridge  Natural  History,  Macmillan;  Lang,  Lehrbuch 
der  Vergleichenden  Anatomie,  Fischer;  or  the  English  transla- 
tion, Macmillan;  Korschelt  und  Heider,  Lehrbuch  der  Vergleich- 
enden Entwicklungsgeschichte,  Fischer;  or  the  English  trans- 
lation, Macmillan;  Delage  et  Herouard,  Traite  de  Zoologie 
Concrete,  Schmidt;  Pratt,  A  Manual  of  Common  Invertebrate 
Animals,  McClurg  &  Co.;  MacBride,  Text-book  of  Embryology, 
Vol.  I,  Macmillan;  Verrill  and  Smith,  Invertebrate  Animals 
of  Vineyard  Sound,  Bui.  U.  S.  F.  C,  1871;  and  Sumner,  Osborn, 


PREFACE  11 

Cole  and  Davis,  A  Biological  Survey  of  the  Waters  of  Woods 
Hole  and  Vicinity,  Bui.  U.  S.  Bur.  Fish.,  30,  1911. 

It  has  been  my  part  to  put  the  original  directions  into  book 
form  and  to  see  that  desirable  changes  were  made  in  them, 
but  much  credit  belongs  to  the  men  who  have  been  associated 
with  me  in  the  instruction  work  at  the  Marine  Biological 
Laboratory. 

The  Author. 


fe 


^S5^ 


CONTENTS 


PAGE 

PROTOZOA 17 

Sarcodina 22 

Amoeba  proteus 22 

Foraminifera 23 

Actinosphaerium  or  Actinophrys 24 

Infusoria 25 

Paramecium 25 

Spirostomum 27 

Vorticella 28 

Oxytricha 29 

Ephelota 30 

Sporozoa 31 

Gregarina 31 

PROTOPHYTA 32 

Euglena 32 

Volvox 33 

Ceratium 34 

Noctiluca 35 

PORIFERA   36 

Sycon  (Grantia) 37 

COELENTERATA 41 

Hydrozoa 43 

Hydra  (Fresh-water  Polyp) 43 

Obelia 45 

Campanularia 47 

Sertularia 48 

Gonionemus ' 48 

Tubularia  (Parypha) 51 

Bougainvillia 52 

Hydractinia 53 

Hydrocorallina 54 

SlPHONOPHORA 54 

Scyphozoa 55 

Aurelia 55 

Actinozoa 59 

Metridium   (Sea-anemone) 59 

CTENOPHORA 63 

Pleurobrachia -> 63 

Mnemiopsis 63 

PLATYHELMINTHES 66 

TURBELLARIA 67 

Planaria  maculata 67 

Bdelloura  or  Syncoelidium 68 

Trematoda 70 

Pneumoneces 71 

Cryptocotyle 73 

Cestoda 73 

Crossobothrium  laciniatum 74 

13 


14  CONTENTS 

Platyhelminthes  (Continued).  page 

Nemertinea 77 

Tetrastemma 77 

NEMATHELMINTHES 79 

Ascaris 79 

Trichinella 80 

Metoncholaimus 81 

TROCHELMINTHES : 84 

ROTIFERA 84 

Brachionus 84 

MOLLUSCOIDA 86 

Bryozoa '. 86 

Bugula ." 86 

Plumatella * 88 

Brachiopoda : 89 

Terebratulina 89 

ANNELIDA 89 

Chaetopoda 91 

Nereis  virens  (Clam-worm) 91 

Autolytus  cornutus 95 

Lepidonotus  (Polynoe)  squamatus 96 

Diopatra  cuprea 98 

Chaetopterus 99 

AmphiCrite  ornata 100 

Cistenides  (Pectinaria)  gouldi 101 

Clymenella  torquata 101 

Arenicola  cristata  (Lug-worm) 102 

Parasabella  microphthalma 107 

Hydroides 108 

Spirorbis 109 

Lumbricus  (Earthworm) 109 

Macrobdella  (Leech) 115 

Gephyrea 119 

Phascolosoma 119 

MOLLUSCA 122 

Pelecypoda 124 

Venus  mercenaria  (Quahog) 124 

Yoldia  limatula 133 

Mytilus  or  Modiolus  (Mussels) 134 

Pecten  gibbus  borealis  (Scallop) 136 

Ostrea  virginica  (Oyster) 137 

Solemya 138 

Mya  arenaria  (Long  Clam) 138 

Ensis  directus  (Razor-shell  Clam) 140 

Cumingia  tellinoides 141 

Amphineura 142 

Chaetopleura  (Chiton) 142 

Gastropoda 143 

Busycon  (Fulgur,  Sycotypus)  (Whelk) 143 

Cephalopoda 153 

Loligo  pealei  (Squid) 153 


CONTENTS  15 

PAGE 

ARTHROPODA 165 

Crustacea 167 

Homarus  aniericanus  (Lobster) 167 

Callinectes  sapidus  (Blue  Crab) 175 

Pagurus  (Hermit  Crab) 179 

Emerita  (Hippa,  Sand  Mole) 180 

Chloridella  (Squilla) 181 

Michtheimysis  (or  Heteroinysis) 182 

Talorchestia  (Beach-flea) 182 

Porcellio  or  Oniscus  (Sow-bug) 184 

Caprella  (Goat  Shrimp) 184 

Branchipus  (Fairy  Shrimp) 185 

Daphnia 186 

Cyclops  (Water-flea) 186 

Argulus  (Fish-louse) 187 

Lepas  (Goose  Barnacle) 188 

Arachnida  . 189 

Limulus  (Horseshoe  Crab) 189 

Buthus  (Scorpion) 195 

Epeira  (Round-web  Spider) 196 

Phoxichilidium 198 

Myriapoda 199 

Lithobius  (Centipede,  Earwig) 199 

Julus  (Thousand-legs) 199 

Insecta 200 

Acridium  (Grasshopper) 200 

Apis  mellifica  (Honey-bee) 206 

ECHINODERMATA 211 

ASTEROIDEA 212 

Asterias  (Starfish) 212 

Ophiuroidea 219 

Ophiura  (Serpent-star) 219 

Echinoidea 220 

Arbacia  or  Strongylocentrotus  (Sea  Urchin) 220 

HOLOTHTTROIDEA 226 

Thyone  (Sea  Cucumber) 226 

CHORDATA '. 231 

Enteropneusta 233 

Dolichoglossus  (Balanoglossus)  kowalevskii 233 

Urochorda 234 

Molgula  manhattensis 234 

Perophora 238 

Botryllus 239 

Amaroucium  (Sea  Pork) 240 

Salpa  cordiformis 242 

Cephalochorda 243 

Amphioxus  lanceolatus 243 

NOTES  FOR  GUIDANCE  IN  MAKING  PERMANENT  PREPA- 
RATIONS   245 

GLOSSARY 251 

INDEX 269 


INVERTEBRATE  ZOOLOGY 


PROTOZOA 

Unicellular  Animals 

Subphylum  1.  Zoomastigophora   (Animal  Flagellates). 

Animal  flagellates  with  no  chromatophores 
or  chlorophyl.  Locomotor  organs  of  adult 
phases  consist  of  one  or  more  motile  struc- 
tures called  flagella.  (The  animal  flagel- 
lates are  similar  in  other  general  respects 
to  the  plant  flagellates — Phytomastigophora 
of  many  older  zoological  classifications — 
now  almost  universally  classed  as  members 
of  the  Algae.) 

Class  1.  Protomastigota. 

Order  1.  Protomonadida. 

Minute  forms.  One  flagellum,  or  a  prin- 
cipal flagellum  and  1  or  2  accessory  flagella. 
(Mastigamoeba,  Multicilia,  Trypanosoma, 
Peranema,  Monas,  Cercomonas,  Bodo.) 

Class  2.  Metamastigota. 

Order  1.  Hypermastigida. 

With  numerous  flagella  and  complicated  in- 
ternal    structure.       All     but     one     genus 
(Lophomonas)  parasitic  in  termites.    (Loph- 
omonas,  Trichonympha,  Joenia.) 
Order  2.  Polymastigida. 

Minute  forms  with  highly  developed  kinetic 
elements.  3  to  8  flagella.  Characteristic 
parasites  of  digestive  tract.  (Giardia,  Trich- 
omonas, Pyrsonympha,  Streblomastix.) 

Subphylum  2.  Sarcodina. 

No  permanent  locomotor  organs  in  adult 
phase  of  the  life  history;  the  cells  moving 
and  ingesting  food  by  temporary  pseudo- 
podia.  "Young"  phases  may  be  amoeboid 
or  flagellate.  (Minchin,  pp.  178  and  234r- 
237.) 
2  17 


18 


PROTOZOA 


Class  1.  Actinopod. 

Chiefly  spherical  floating  forms  with  slender 
unbranched  radiating  pseudopodia  supported 
by  an  internal  axial  filament. 

Subclass  1.    Heliozoa. 

Fresh-water  forms  without  a  "central  cap- 
sule" separating  ectoplasm  and  endoplasm. 
(Actinosphaerium,  Actinophrys,  Clathru- 
lina.) 

Subclass  2.    Radiolaria. 

Marine  forms  with  a  central  capsule.   (Thal- 
assicola.) 
Class  2.  Rhizopoda. 

Forms  with  branched,  rootlike  pseudopodia. 
Locomotion  chiefly  by  creeping. 

Subclass  1.    Proteomyxa. 

Forms  with  raylike  pseudopodia  frequently 
branching  and  with  no  axial  filaments.  (Nu- 
clearia.) 

Subclass  2.    Mycetozoa. 

Semiterrestrial  forms  with  myxopodia  and 
Plasmodium  formation.     (Stemonitis.) 

Subclass  3.    Foraminifera. 

Chiefly  marine  forms  with  reticulose  pseudo- 
podia and  complex  tests.  (Lecythium,  Glo- 
bigerina.) 

Subclass  4.   Amoebaea. 

Simple     amoeboid     forms,     typically     with 
lobose    pseudopodia;    with    or    without    a 
simple  test.     (Amoeba,  Arcella,  Difflugia.) 
Subphylum  3.  Infusoria. 

With  motile  organs  in  the  form  of  cilia  dur- 
ing all  or  part  of  the  life  cycle.  Nucleus 
generally  dimorphic  (macronucleus  and 
micronucleus) .  Reproduction  is  by  simple 
transverse  division  or  by  budding. 

Class  1.  Ciliata. 

With  cilia  throughout  the  life  history. 
Subclass  1.    Holotricha. 

Cilia  are  of  approximately  equal  length  and 
equally  distributed  over  body.  Trichocysts 
frequently  present.  No  adoral  zone  of  mem- 
branelles.  (Opalina,  Prorodon,  Lacrymaria, 
Coleps,  Lionotus,  Nassula,  Frontonia,  Col- 
pidium,  Didinium,  Paramecium). 


PROTOZOA 


19 


Subclass  2.    Spirotricha. 

With  adoral  zone  of  membranelles  right- 
wound  toward  the  mouth.  Peristome  not 
drawn  out  like  a  funnel.  Includes  as  chief 
orders  Heterotrichida,  Oligotrichida  and 
Hypotrichida.  (Spirostomum,       Stentor, 

Oxytricha,  Stylonychia,  Euplotes.  Halteria.) 

Subclass  3.    Peritricha. 

With  adoral  zone  of  membranelles  left- 
wound  toward  the  mouth.  Cilia  usually 
limited  to  those  in  the  adoral  zone.  (Vor- 
ticella,  Zoothamnium,  Carchesium,  Epis- 
tylis.) 

Subclass  4.    Chonotricha. 

Adoral  zone  right- wound  toward  the  mouth. 
Peristome  drawn  out  like  a  funnel.     (Spiro- 
chona.) 
Class  2.  Suctoria    (Acinetaria,  Tentaculifera) . 

Usually  possessing  cilia  only  during  embry- 
onic stages.    Tentacles  adapted  for  piercing 
and    sucking    are    present    in    the    adults. 
(Podophrya,  Ephelota,  Acineta.) 
Subphylum  4.  Sporozoa. 

Without  cilia  or  flagella  in  the  "adult"  period 
of  the  life  cycle.    Reproduction  is  by  spore 
formation  (multiple  fission).    All  are  endo- 
parasites. 
Class  1.  Telosporidia. 

Sporulation  phase  of  the  life  cycle  is  dis- 
tinct and  follows  the  trophic  phase. 

Subclass  1.    Gregarinina. 

Typically   lumen-dwelling   parasites   of   in- 
vertebrates.     Reproduction    by    sporogony 
alone  or  by  sporogony  and  schizogony. 
Order  1.  Eugregarinida. 

Comprises  most  of  the  gregarines.    Sporozo- 
ites,  usually  8  in  number,  formed  only  after 
sexual   phenomena.      (Monocystis,   Gregar- 
ina.) 
Order  2.  Schizogregarinida. 

Parasites  of  the  digestive  tract  of  arthro- 
pods, annelids  and  tunicates.  With  an 
asexual  cycle.     (Schizocystis.) 


20  PROTOZOA 

Subclass  2.    Coccidiomorpha. 

Found  in  all  groups  of  animals.  Typically 
intracellular  in  all  stages  of  life  history. 
Life  cycle  varies  greatly  in  complexity. 

Order  1.  Coccidiida- 
Suborder  1.  Eimeriina. 

With  few  exceptions,  epithelial-cell  para- 
sites with  sporoblasts  in  a  capsule. 
(Eimeria.) 

Suborder  2.  Hemosporidia. 

Typically  blood  parasites  of  vertebrates.  In 
many  forms  the  entire  sexual  period  of  the 
life  cycle  takes  place  in  an  intermediate 
host,  as  the  mosquito.     (Plasmodium.) 

Suborder  3.  Babesiina. 

Blood  parasites  of  vertebrates.  They  lack 
melanin  pigment.      (Babesia.) 

Order  2.  Adeleida. 

With  no  flagellated  gametes.  Sexual  proc- 
ess similar  to  pseudoconjugation  in  gre- 
garines.     (Adelea.) 

Class  2.  Cnidosporidia. 

(This  and  the  following  class  were  formerly 
classed  under  Neosporidia.)  Sporulation 
takes  place  during  the  "trophic"  phase  of 
life  cycle.    Sporozoites  are  amoebulae. 

Order  1.  Myxosporidia. 

Typically  parasites  of  fishes.  Free  or  tis- 
sue-inhabiting. Spore  capsule  with  2  valves. 
Usually  2  polar  capsules.     (Myxidium.) 

Order  2.  Actinomyxida. 

Parasites  of  annelids.  Spores  with  3  polar 
capsules.     (Sphaeractinomyxon.) 

Order  3.  Microsporidia. 

Minute  organisms — rarely  more  than  1 
polar  capsule,  sometimes  none.     (Nosema.) 

Class  3.  Acnidosporidia. 

Includes  the  group  formerly  known  as  the 
Sarcosporidia.  The  initial  stage  of  the  life 
cycle  occurs  in  the  muscle  cells  of  verte- 
brates. Spores  with  a  single  polar  capsule. 
(Sarcocystis.) 


PROTOPHYTA  21 

PROTOPHYTA 

Algae.  In  this  group  are  now  included  flagellates  for- 
merly classed  under  the  Protozoa  as  Phytomastigophora. 
Volvox  (p.  33)  is  now  classed  under  the  Class  Isokontae 
(formerly    under    Order    Phytomonadida) ;    Euglena    under 

Class  Eugleninae  (formerly  Order  Euglenida) ;  Ceratium  and 
Noctiluca  under  Class  Dinophyceae  (formerly  Order  Dino- 
flagellida) . 

Blochmann:  Die  Mikroskopische  Tierwelt  des  Siisswassers.  Abt.  1. 
Protozoa,  1895. 

Biitschli:    Protozoa.  Bronn's  Thierreich,  1889. 

Calkins:    Biology  of  the  Protozoa,  1933. 

:    Marine  Protozoa  of  Woods  Hole.    Bull.  U.  S.  Fish.  Com.,  1901. 

Cleveland:  Effects  of  Oxygenation  and  Starvation  on  Intestinal  Flagel- 
lates of  Termopsis.    Biol.  Bull.,  48,  1925. 

Conn:  Fresh  Water  Protozoa  of  Connecticut.  Bull.  State  Nat.  Hist. 
Surv.,  1905. 

Doflein  and  Reichenow:    Lehrbuch  der  Protozoenkunde,  1929. 

Edmondson:    Protozoa   of  Iowa.     Davenport  Acad.  Sci.,   1906. 

Hartmann  and  Kisskalt:  Praktikum  der  Bakteriologie  und  Proto- 
zoologie,  1910. 

Jennings:    Behavior  of  the  Lower  Organisms,  1906. 

:  Life  and  Death,  Heredity,  and  Evolution  in  Unicellular  Organ- 
isms, 1920. 

Kent:    Manual  of  the  Infusoria,  1881. 

Kudo:    Handbook  of  Protozoology,  1931. 

Lankester:    Treatise  on  Zoology.     1.  Protozoa. 

Leidy:    Fresh  Water  Rhizopods  of  North  America,  1879. 

Maupas:  Studies  on  Infusoria,  in  Arch.  Zool.  Exp.  et  Gen.,  1883,  1888, 
and  1889. 

Minchin:    Protozoa,  1912. 

Prowazek:  Einfuhrung  in  die  Physiologie  der  Einzelligen  (Protozoen), 
1910. 

:    Taschenbuch   der  Mikroskopischen  Technik  der  Protistenunter- 

suchung,  1909. 

Stokes:  Contribution  Toward  a  History  of  the  Fresh  Water  Infusoria 
of  the  United  States.    Jour.  Trenton  Nat.  Hist.  Soc,  1,  1888. 

Ward  and  Whipple:    Fresh- Water  Biology,  1918. 

Whipple:    Microscopy  of  Drinking  Water,  4th  ed.,  1927. 

Woodruff:  Observations  on  the  Origin  and  Sequence  of  the  Protozoan 
Fauna  of  Hay  Infusions.    Jour.  Exp.  Zool.,  12,  1912. 


22  PROTOZOA 

SARCODINA 

AMOEBA  PROTEUS 

Amoebae  are  usually  just  discernible  under  the  low  power 
of  the  microscope  as  irregular,  semi-transparent,  granular 
bodies.  Find  a  specimen  in  the  material  provided,  which  is 
known  to  contain  amoebae,  and  determine  the  following 
points : 

1.  With  the  high  power  observe  the  peculiar  method  of 
locomotion,  the  constant  but  slow  change  in  the  shape  of  the 
body  by  means  of  projections,  pseudopodia,  or  "false  feet." 

Make  sketches  at  intervals  of  one  or  two  minutes  to  show 
the  changes  in  the  form  of  the  body. 

2.  Observe  the  peripheral  zone  of  hyaline  protoplasm,  the 
ectoplasm,  and  compare  this  with  the  inner  protoplasm,  the 
endoplasm.  Observe  in  detail  the  formation  of  a  pseudo- 
podium.  Does  the  endoplasm  extend  into  the  pseudopodium? 
Can  you  explain  how  the  movement  is  caused? 

3.  Find  a  clear  space  which  appears  and  disappears  at  in- 
tervals; this  is  the  contractile  vacuole.  Determine  the  length 
of  time  between  successive  contractions.  Are  the  intervals 
regular?  When  the  vacuole  contracts  what  becomes  of  the 
contents?    What  is  its  function? 

4.  Note  the  nucleus.  In  order  to  determine  the  actual 
shape  of  this  structure  observe  it  carefully  as  it  is  moved 
through  the  endoplasm.  The  nucleus  of  Amoeba  proteus  may 
appear  at  one  time  with  a  circular  outline  and  in  another 
view  may  seem  much  flattened  or  even  somewhat  biconcave. 

5.  Food  materials  in  process  of  digestion  are  readily  seen. 
Of  what  do  they  consist?  They  are  contained  in  food  vacu- 
oles. By  careful  watching,  it  is  often  possible  to  observe  the 
manner  in  which  food  is  ingested  and  the  manner  in  which 
the  undigested  matter  is  egested. 

6.  Observe  the  crystals  within  the  endoplasm.  What  is 
their  shape?    Is  more  than  one  type  present? 

7.  Determine  whether  the  surface  of  the  amoeba  shows 
ectoplasmic  ridges. 


AMOEBA,  THE  FORAMINIFERA  23 

The  large  free-living  amoebae  are  identified  chiefly  by 
the  following  characters:  (a)  type  of  pseudopodia  and  the 
appearance  of  these  when  the  animal  is  crawling  freely,  (b) 
the  shape  of  the  nucleus,  (c)  presence  or  absence  of  ecto- 
plasmic  ridges,  (d)  character  of  the  contained  crystals. 

Make  a  careful  drawing  of  an  Amoeba. 

If  time  and  material  permit,  study  Amoeba  dubia,  A. 
verrucosa,  Arcella,  and  Dijflugia,  and  compare  them  with 
A.  proteus.  Do  you  understand  how  the  shells  of  the  last 
two  genera  are  made,  and  of  what  service  they  are? 

Drawings  of  these  forms  are  desirable. 

Calkins :  Genera  and  Species  of  Amoeba.  Trans.  Fifteenth  International 
Congress  on  Hygiene,  1912.  The  Fertilization  of  A.  proteus.  Biol. 
Bull.,  13,  1907. 

Dawson,  Kessler  and  Silberstein:  Mitosis  in  Amoeba  dubia.  Biol.  Bull., 
69,  1935. 

Dellinger:  Locomotion  of  Amoeba  and  Allied  Forms.  Jour.  Exp.  Zool., 
3,  1906. 

Metcalf:    Amoeba  Studies.     Jour.  Exp.  Zool.,  9,  1910. 

Popoff:  Ueber  den  Entwicklungscyclus  von  A.  minuta.  Arch.  f.  Protis- 
tenk.,  22,  1911. 

Schaeffer:  Notes  on  the  Specific  and  Other  Characters  of  Amoeba  Pro- 
teus, etc.    Arch.  f.  Protistenk.,  37,  1916. 

:    Taxonomy  of  the  Amebas.    Carnegie  Inst.,  Washington,  1926. 

THE  FORAMINIFERA 

With  very  few  exceptions  Foraminifera  are  marine  and 
provided  with  shells.  Specimens  may  be  obtained  from 
material  scraped  from  wharf  pilings.  Examine  them  with  a 
low  power  by  reflected  light. 

1.  Carefully  examine  various  shells,  compare  them  with 
each  other  and  with  figures.  Notice  the  great  variety  in  size 
and  shape  and  determine  how  the  chambers  must  have  been 
added  during  growth. 

2.  Observe  a  single  opening  in  a  shell,  and  determine 
whether  the  general  surface  has  any  finer  perforations.  Be 
sure  to  understand  the  relation  of  the  live  animal  to  the  shell. 

Make  drawings  of  several  types  of  shells. 


24  PROTOZOA 

Cushman:    Foraminifera,  Their  Classification  and  Economic  Use,  1928. 
Farmer:    Foraminifera,  pp.  133-139,  Lankester's  Treatise. 
Flint:    Recent  Foraminifera.    Rep.  U.  S.  Nat.  Mus.,  1897. 
Calkins:    Marine  Protozoa  of  Woods  Hole.    Bull.  U.  S.  F.  C,  1901. 

ACTINOSPHAERIUM  OR  ACTINOPHRYS 

Find,  as  usual,  with  the  low  power,  and  increase  the  mag- 
nification as  occasion  demands.  On  account  of  its  large  size 
it  is  better  to  study  Actinosphaerium  in  a  culture  dish  or 
depression  slide  using  the  low  power  only. 

1.  Note  the  many  fine  radiating  pseudopodia.  These  are 
quite  stiff  compared  with  those  of  Amoeba  and  for  a  con- 
siderable time  show  little  change,  not  being  pushed  out  and 
retracted  constantly  as  in  Amoeba.  Is  the  animal  flat  or 
spherical? 

2.  Both  ectoplasm  and  endoplasm  are  so  filled  with  vacu- 
oles that  they  present  a  frothy  appearance  characteristic  of 
most  Heliozoa.  The  endoplasm  of  all  Protozoa  is  alveolar 
in  structure,  but  in  Actinosphaerium  the  vacuoles  are  ex- 
ceptionally large,  though  not  as  large  as  those  in  the  ecto- 
plasm. In  Actinophrys  the  endoplasm  is  not  so  sharply 
separated  from  the  ectoplasm. 

3.  The  nucleus  of  Actinophrys  is  present  in  the  center  of 
the  organism,  but  it  is  somewhat  difficult  to  demonstrate  in 
the  live  animal.  In  Actinosphaerium  there  are  many  nuclei. 
These  can  be  seen  well  only  in  stained  specimens. 

4.  At  some  point  near  the  periphery,  the  contractile  vacu- 
ole can  usually  be  seen.  When  it  is  found  notice  its  action, 
and  immediately  after  it  has  contracted  look  among  the 
pseudopodia  of  that  region  for  indications  of  its  extruded 
contents. 

Draw  a  specimen,  indicating  all  of  the  points  observed. 

5.  When  the  contractile  vacuole  discharges,  or  when  any 
foreign  body  touches  the  ends  of  the  pseudopodia,  notice  the 
way  in  which  this  type  of  pseudopodium  is  moved.  What 
does  this  indicate  in  regard  to  its  structure?  How  far  do 
the   pseudopodia   extend?     They   may    be    seen   to    contain 


ACTINOSPHAERIUM,    PARAMECIUM  25 

minute  granules  when  studied  with  the  high  power  and  best 
light. 

6.  If  possible,  observe  the  process  of  catching  food  with 
the  tips  of  the  pseudopodia  and  the  manner  in  which  it  is 
drawn  toward  the  body.  Note  any  motion  on  the  surface  of 
the  body  as  the  food  is  drawn  closer,  and  also  the  manner  in 
which  the  food  is  finally  ingested.  Are  there  any  indications 
that  the  pseudopodia  extend  as  still  finer  filaments  beyond 
the  point  to  which  it  is  possible  to  trace  them  with  the  high- 
est magnification  at  hand?  If  the  capturing  of  food  is  ob- 
served, make  a  series  of  diagrams  to  illustrate  the  process. 
(Minchin,  p.  50.) 

If    possible,    observe    a    specimen    undergoing    division. 

Draw. 

It  is  desirable  to  examine  Clathrulina,  noting  the  stalk 
and  skeleton.    Look  over  figures. 

R.  Hertwig:  Ueber  die  Kernteilung,  Richtungskorperbildung  und  Be- 
fruchtung  bei  Actinosphaerium.  Abt.  d.  Math.  Phys.  Kl.  d.  Ak.  d. 
Wiss.,  Munchen,  19,  1898. 

INFUSORIA 

PARAMECIUM 

Place  a  drop  of  the  culture  on  a  slide,  cover,  and  ex- 
amine with  the  low  power. 

1.  In  an  animal  not  closely  confined  note  the  shape  and 
movements.  Is  it  possible  to  distinguish  an  anterior  and  a 
posterior  end?  A  forward  and  backward  movement?  Is  one 
side  of  the  animal  kept  constantly  uppermost?  Is  there  a 
dorsal  and  a  ventral  surface?  Do  the  animals  change  their 
shape  either  permanently  or  temporarily?  Individuals  tend 
to  collect  about  air  bubbles  and  at  the  edge  of  the  cover- 
glass.    Why? 

Indicate  by  a  sketch  all  the  points  which  can  be  deter- 
mined with  the  low  power. 

2.  Draw  off  all  superfluous  water  by  means  of  filter  paper, 
add  a  trace  of  powdered  carmine,  and  then  find  a  specimen 


26  PROTOZOA 

which  is  narrowly  confined  and  examine  it  with  the  high 
power. 

The  particles  of  carmine  are  taken  into  the  body.  Deter- 
mine how  and  where.  Note  that  the  carmine  collects  in  jood 
vacuoles.  What  do  you  think  is  probably  the  nature  of 
the  fluid  in  the  vacuoles?  In  watching  them  do  you  notice 
any  definite  movement  of  the  protoplasm?  Try  to  see  the 
undigested  material  ejected. 

3.  Determine  the  arrangement  of  the  cilia,  and  the  nature 
of  their  motion.  Is  there  a  reversal  of  the  direction  of  the 
stroke,  etc.?1 

4.  Observe  the  contractile  vacuoles.  How  many  are 
there?  Is  their  position  constant?  What  is  their  action? 
In  compressed  specimens  the  contractile  vacuoles  and  their 
reservoirs  are  usually  conspicuous.  Note  the  order  of  ap- 
pearance and  disappearance  of  the  vacuoles  and  reservoirs. 

5.  Focus  carefully  on  the  margin  of  the  body  and  note  a 
very  thin  outer  cuticle.  A  thick  layer,  the  ectoplasm,  de- 
void of  granules  but  containing  radially  arranged,  minute, 
oval  bodies,  the  trichocysts,  is  just  internal  to  the  cuticle. 
The  inner  mass  of  protoplasm,  containing  the  contractile  and 
food  vacuoles,  and  small  granules,  is  the  endoplasm. 

6.  If  possible  distinguish  the  clear,  centrally  located 
nucleus  (macronucleus) . 

Make  a  sketch  showing  all  of  the  above  points. 

7.  Kill  the  animal  by  running  a  drop  of  methyl  green 
under  the  coverglass.  What  happens  to  the  cilia?  It  is  pos- 
sible to  watch  the  process  of  staining  in  the  macronucleus 
if  specimens  are  observed  very  soon  after  the  methyl  green 
is  added.  In  Paramecium  caudatum  the  micronucleus  may 
also  be  seen.  If  P.  aurelia  is  being  studied  the  micronuclei 
usually  cannot  be  detected  by  this  method. 

1  It  is  possible  to  decrease  the  rate  of  movement  of  the  animals  by 
placing  them  in  a  solution  of  quince-seed  jelly  or  by  teasing  a  small 
piece  of  lens-cleaning  paper  in  the  medium  containing  the  paramecia. 
Specimens  so  treated  remain  alive  for  some  time. 


PARAMECIUM,    SPIROSTOMUM  27 

8.  Place  a  drop  of  culture  containing  a  number  of  animals 
on  a  slide  and  put  a  drop  of  Waterman's  fountain  pen  fluid 
on  a  coverglass.  Invert  the  coverglass  and  place  it  with  its 
hanging  drop   of  ink  on   the   slide.     What  happens  to  the 

trichocysts? 

Make  a  drawing  showing  the  structures  revealed  by  the 

treatment  in  these  two  cases. 

9.  Observe,  if  possible,  animals  dividing  and  conjugating. 

10.  Study  demonstrations  of  permanently  stained  speci- 
mens for  finer  structure. 

Calkins  and  Cull:    Conjugation  of  P.  caudatum.    Arch.  f.  Protistenk., 

10,  1907. 
Jennings:    Effect  of  Conjugation  in  Paramecium.    Jour.  Exp.  Zool.,  14, 

1913. 
Metalinkow :    Contributions  a  l'etude  de  la  digestion.     Arch.  d.  Zool. 

Exp.  et  Gen.,  9,  1912. 
Wenrich:    Eight  Well  Defined  Species  of  Paramecium.     Trans.  Amer. 

Micr.  Soc,  47,  1928. 
Woodruff:     Paramecium    aurelia    and    Paramecium    caudatum.      Jour. 

Morph.,  22,  1911. 
Woodruff  and  Erdmann:    A  Normal,  Periodic  Reorganization  Process 

(Endomixis)     Without    Cell    Fusion    in    Paramecium.      Jour.    Exp. 

Zool.,  17,  1914. 
Woodruff:    The  Structure,  Life  History,  and  Intrageneric  Relationships 

of  Paramecium  Calkinsi,  sp.  nov.    Biol.  Bull.,  voi.  41,  1921. 

SPIROSTOMUM 

1.  Compare  Spirostomum  with  Paramecium,  noting  the 
method  of  locomotion,  the  shape  of  the  body,  the  ciliation, 
the  buccal  groove  and  mouth,  and  the  large  excretory  reser- 
voir, filling  the  posterior  end  of  the  body  and  in  communica- 
tion with  the  anterior  end  of  the  body  by  a  canal. 

2.  Note  the  highly  refractive,  long,  bandlike  (monili- 
form)  macronucleus.  In  a  less  common  species  of  Spiro- 
stomum the  macronucleus  is  similar  to  that  of  Paramecium. 

3.  Note  the  sudden  contractions  of  the  body.  When  these 
occur  spiral  lines  appear  on  the  surface.  Can  you  distinguish 
these  lines  when  the  animal  is  extended?  These  are  primi- 
tive structures  {myonemes)   functioning  as  muscles. 


28  PROTOZOA 

Make  a  drawing  of  the  extended  animal  and  a  diagram 
showing  the  form  when  contracted.  (See  Doflein  and  Reich- 
enow.) 

VORTICELLA 

Place  a  number  of  individuals  on  a  slide  and  cover  loosely 
to  avoid  crushing.  As  usual,  study  first  with  the  low  power 
and  then  with  the  high. 

1.  Notice  that  the  body  of  Vorticella  has  the  general 
shape  of  an  inverted  bell.  The  covering  of  the  body  is  a 
very  thin  transparent  layer,  the  cuticle,  underneath  which  is 
the  peripheral  layer  of  ectoplasm  enveloping  the  more  fluid 
and  granular  endoplasm. 

2.  The  peristome  is  the  rounded  rim  about  the  base  of  the 
bell. 

3.  The  elevated  and  inclined  area  included  within  the 
peristome,  and  ciliated  around  the  edge,  is  the  disk.  It  is 
somewhat  convex. 

4.  The  marked  depression  between  the  disk  and  the  per- 
istome is  the  vestibule.  It  is  also  lined  with  cilia.  The  ves- 
tibule defines  the  ventral  surface  of  the  animal. 

5.  The  gullet,  a  slender  canal,  leads  from  the  vestibule 
toward  the  center  of  the  body. 

6.  The  feces  escape  from  the  body  by  the  side  of  the  ves- 
tibule.   The  opening  is  temporary. 

7.  Within  the  endoplasm  are  situated  the  clear  contractile 
vacuole,  several  food  vacuoles,  the  long  U-shaped  macronu- 
cleus,  and  the  small  round  micronucleus.  The  macronucleus 
may  be  made  more  distinct  by  treating  with  methyl  green. 

8.  The  stalk  is  composed  of  a  sheath,  which  is  continuous 
with  the  cuticle  of  the  body,  and,  within  the  sheath,  the  con- 
tractile axis  or  myoneme,  which  is  continuous  with  the  body 
ectoplasm.  Notice  that  this  myoneme  is  situated  within  the 
sheath  in  a  very  loose  spiral,  and  that  the  stalk  quickly  con- 
tracts into  a  close  spiral  when  the  animal  is  stimulated.  Ob- 
serve  also  the   manner   in   which   the   peristome   folds   over 


VORTICELLA,    OXYTRICHA 


29 


simultaneously  with  the  contraction  of  the  stalk.  What  pur- 
pose does  the  contraction  of  the  stalk  serve? 

Vorticella  is  distinguished  from  its  allied  genera  by  its 
simple  unbranched  stalk  and  also  by  the  spiral  form  as- 
sumed by  the  contracted  stalk.  In  which  order  of  the  Ciliata 
does  the  ciliation  of  Vorticella  place  it?  Compare  with 
Zoothamnium. 

Make  a  drawing  of  an  expanded  individual  and  a  sketch 
to  show  the  condition  when  contracted.     (Minchin,  p.  434.) 

9.  Study,  by  means  of  finely  powdered  carmine,  the  vor- 
tex currents  set  up  by  the  cilia.  Note  how  the  particles  are 
collected  in  the  gullet,  and  at  intervals  are  forced  in  rounded 
masses  into  the  endoplasm  to  form  food  vacuoles.  Is  there 
a  definite  circulation  in  the  endoplasm? 

10.  Endeavor  to  find  several  stages  of  reproduction  by 
division. 

Large  fresh-water  species  of  Vorticella  are  preferable  for 
study,  but  marine  species  may  be  substituted  when  neces- 
sary. If  time  and  material  permit,  study  Lichnophora,  a 
marine  peritrichous  form  parasitic  on  Crepidula.  (See  Cal- 
kins' Protozoa,  p.  203.) 

Schroder:    Beitrage  zur  Kenntnis  von  V.  monilata.    Arch.  f.  Protistenk., 
7,  1906. 

OXYTRICHA 

Infusoria  belonging  to  the  genus  Oxytricha,  or  the  genera 
Stylonychia,  Pleurotricha,  Euplotes,  etc.,  may  be  used  for 
the  following  study.  These  forms  belong  to  the  order  Hypo- 
trichida.  Hypotrichous  forms  are  among  the  most  highly 
organized  of  the  class  Infusoria, "  as  well  as  of  the  entire 
phylum  of  Protozoa,  and  present  a  complexity  of  structure 
and  function  which  probably  is  not  exceeded  within  the  limits 
of  a  single  cell  elsewhere  in  the  animal  series. 

1.  In  an  animal  which  is  becoming  quiet,  note  the  mode 
of  locomotion,  the  shape  of  the  body,  the  buccal  groove,  the 
contractile  vacuole,  etc.,  as  in  other  forms  studied.    Compare 


30  PROTOZOA 

the  ciliation  with  that  of  other  forms.     Refer  to  Calkin's 
Biology  of  the  Protozoa,  pp.   152-162,  and  understand  the 
relation  of  cirri,  membranelles,  etc.,  to  cilia. 
Draw,  showing  the  structure  in  detail. 

2.  Run  some  methyl  green  under  the  coverglass.  What 
is  the  shape  of  the  macro-nucleus?  The  shape  varies  con- 
siderably in  the  different  genera.  Is  it  possible  to  distinguish 
the  micronucleif 

3.  Prepare  a  fresh  slide  and  observe  in  detail  the  charac- 
teristic movements  and  manner  of  creeping  over  various  ob- 
jects. As  the  animal  turns  sidewise,  note  the  marked 
dorso-ventral  compression  of  the  body. 

Represent    this    diagrammatically    beside    the    previous 

drawing. 

It  is  desirable  to  examine  permanently  stained  prepara- 
tions for  division  stages,  finer  details  of  the  nuclei,  etc. 

Maier:    Ueber  den  feineren  Bau  der  Wimperapparate  der  Infusorien. 

Arch.  f.  Protistenk.,  2,  1903. 
Wallengren :    Zur  Kenntnis  des  Neubildungs  und  Resorptionsprocess  bei 

den  Teilung  der  Hypotrichen  Infusorien.    Zool.  Jahrb.,  15,  1901. 

EPHELOTA 

Mount  a  small  piece  of  hydroid  (e.  g.,  Bougainvillia, 
Campanularia,  Sertularia,  or  Obelia)  under  a  supported 
coverglass  and  with  a  low  power  observe  the  suctorians 
attached  by  delicate  stalks.  Select  a  field  where  the  animals 
are  abundant  and  study  under  a  high  power. 

1.  Note  the  general  shape  of  the  cell  and  the  distribution 
of  the  tentacles.  Are  all  of  the  tentacles  of  one  kind?  Ob- 
serve the  movements  of  the  tentacles  and  their  use.  Is  there 
any  morphological  relation  between  tentacles  and  cilia?  (See 
Minchin's  Protozoa,  p.  458.) 

Draw. 

2.  Study  the  method  of  exogenous  budding.  What  is  the 
relation  of  this  type  to  simple  division?  Is  the  number  of 
buds  in  process  of  formation  the  same  on  all  specimens?    If 


EPHELOTA,   GREGARINA  31 

a  budding  specimen  is  found  keep  it  well  supplied  with  water 
and  watch  for  the  escape  of  the  buds  as  free-swimming 
ciliated  embryos. 

3.  Fix,  stain,  and  mount  in  balsam  a  piece  of  hydroid  with 
many  Ephelota  attached.  Under  the  high  power  note  the 
character  of  the  macronucleus  and  its  relation  to  the  buds. 
Are  micronuclei  visible? 

4.  Examine  carefully  the  relation  of  the  stalk  to  the  cell 
body.    Compare  with  that  of  Vorticella. 

If  the  material  is  available  study  Podophrya  and  allied 
forms,  with  particular  reference  to  the  method  of  budding. 

Collin:  Etude  monographique  sur  les  Acinetiens.  Arch.  Zool.  Exp.  et 
Gen.,  1911  and  1912. 

Root:  Reproduction  and  Reactions  to  Food  in  the  Suctorian,  Podo- 
phrya Collini,  n.  sp.    Arch.  f.  Protistenk.,  35,  1914. 

SPOROZOA 

GREGARINA 

Remove  the  head  and  posterior  end  of  a  larval  or  adult 
meal  beetle  and  pull  out  the  digestive  tract  with  a  pair  of 
forceps.  Place  the  digestive  tract  on  a  slide,  split  it  open 
lengthwise  with  a  sharp  scalpel,  and  then  spread  it  out,  with 
the  inner  wall  exposed,  and  cover.  The  operation  should  be 
performed  rapidly  to  prevent  the  material  from  drying.  If 
the  beetle  is  infected,  numerous  gregarines  will  be  visible 
under  the  microscope.    Study  with  low  and  high  powers. 

1.  Does  the  animal  move?  A  great  number  of  refractive 
granules  are  present  in  the  protoplasm.  They  are  regarded 
as  reserve  nourishment.    They  can  be  removed  with  acid. 

2.  Note  that  the  body  is  covered  with  a  membrane,  and 
is  divided  into  a  dense  superficial  layer,  the  ectoplasm,  and 
a  central,  more  fluid  mass,  the  endoplasm. 

3.  The  endoplasm  is  separated  into  two  parts  by  a  por- 
tion of  the  ectoplasm.  The  anterior  part  is  termed  the  pro- 
tomerite,  and  the  posterior  part  the  deutomerite.  In  which 
is  the  nucleus  situated? 


32  PROTOZOA 

4.  Is  it  possible  to  distinguish  a  layer  of  myonemes  just 
external  to  the  endoplasm? 

5.  Is  there  another  section  of  the  body  just  anterior  to 
the  protomerite?    If  so,  this  is  the  epimerite. 

6.  Note  that  occasionally  two  (or  more)  individuals  are 
united.    These  aggregations  are  termed  syzygies. 

Before  reproduction  Gregarina  throws  off  the  epimerite, 
leaves  it  in  the  cell  host,  and  falls  into  the  lumen  of  the  di- 
gestive tract.  It  then  encysts,  and  the  protomerite  and  the 
deutomerite  form  one  spore-producing  individual.  The  at- 
tached stage  in  the  life  history  of  Gregarina  is  termed  the 
cephalont,  and  the  detached  stage,  the  sporont.  (Minchin, 
Fig.  7.) 

Make  a  drawing. 

Examine  digestive  tract  of  Phascolosoma  gouldi  for 
Schizocystis  sipunculi,  an  acephaline  gregarine. 

Berndt:    Beitrag  zur  Kenntnis  der  im  Darme  der  Larvre  von  Tenebrio 

molitor  lebenden  Gregarinen.    Arch.  f.  Protistenk.,  1,  1902. 
Minchin:    Sporozoa,  pp.  177-179,  Lankester's  Treatise. 

PROTOPHYTA 

EUGLENA 

Understand  its  habitat  and  with  what  forms  it  is  usually 
associated. 

1.  Observe  the  free-swimming  movements  of  the  organ- 
ism, and  the  euglenoid  changes  in  the  form  of  the  body. 

Make  drawings  showing  the  changes  in  the  shape  of  a 
single  individual. 

2.  Distinguish  anterior  and  posterior  ends.  Is  there  any 
dorso- ventral  differentiation?  Note  the  motile  organ,  the 
flagellum.  Where  is  it  attached?  What  relation  does  it  bear 
to  the  gullet?  How  is  it  directed  during  locomotion  of  the 
organism?  Does  it  serve  any  other  purpose  besides  locomo- 
tion?    (Minchin,  p.  52.) 

3.  The  green  color  of  Euglena  is  due  to  chlorophyl,  and 


EUGLENA,    VOLVOX  33 

mis  enables  it  to  live  in  clear  water,  being  nourished  like 
other  green  plants.     (Minchin,  p.  14.) 

4.  Note  the  absence  of  color  near  the  anterior  and  pos- 
terior ends  of  the  organism.  Near  the  anterior  end  also 
notice  the  red  pigment  spot,  or  stigma.  What  is  its  probable 
function? 

5.  Stain  a  specimen  with  iodine  and  look  for  the  nucleus. 
It  is  somewhat  obscured  by  the  chlorophyl. 

6.  Observe  specimens  in  the  resting  stage. 

Make  a  drawing  showing  all  of  the  points  observed. 
Look  through  the  stock  cultures  for  other  forms  of  plant 
flagellates,  such  as  Trachelomonas,  Phacus,  etc. 

It  is  desirable  to  make  drawings  of  the  different  forms. 

Klebs:  Ueber  die  Organisation  einiger  Flagellatengruppen  und  ihre 
Beziehungen  zu  Algen  und  Infusorien.  Unt.  Bot.  Inst.  Tubingen,  1, 
1883. 

:    Flagellatenstudien.     Zeit.  f.  wiss.  Zool.,  55,  1893. 

Walton:    Review  of  the  Order  Euglenoidina.     Ohio  State  Univ.,  1915. 

Baker:    Studies  in  the  Life  History  of  Euglena.     Biol.  Bull.,  51,  1926. 

VOLVOX 

Volvox  globator  is  better  for  study  than  V.  aureus.  It 
may  be  distinguished  from  the  latter  by  the  larger  size  of 
the  colony,  the  greater  number  of  cells  that  compose  it 
(about  15,000),  the  angular  shape  of  the  individual  cells,  and 
the  stout  connecting  processes  of  protoplasm,  into  which 
chromatophores  may  enter. 

Observe  the  movements  of  colonies  in  a  watch  glass  of 
water,  with  the  naked  eye  and  with  a  low  power  of  the 
microscope. 

1.  Do  the  colonies  tend  to  collect  toward  a  particular  side 
of  the  dish?  What  reason  is  there  for  the  reaction?  Does 
an  individual  Volvox  colony  move  with  reference  to  one  axis? 

2.  Place  a  number  of  colonies  on  a  slide  with  enough 
water  to  allow  them  to  be  covered  without  crushing  them. 
Study  first  with  the  low  and  then  with  the  high  power  and 

3 


34  PROTOZOA 

determine  the  species.     Understand  the  relation  of  the  in- 
dividual cells  to  the  colony.     (See  Doflein  and  Reichenow.) 

Draw  a  figure  showing  several  cells  and  their  protoplas- 
mic connections. 

3.  Compare  in  detail  an  individual  cell  with  Euglena. 

4.  Observe,  if  possible,  certain  cells,  called  parthenogo- 
nidia,  which  are  specialized  for  asexual  reproduction.  These 
divide  and  form  the  daughter  colonies,  which  become  de- 
tached and  swim  in  the  interior  of  the  parent  colony.  They 
are  finally  liberated  by  the  rupture  of  the  wall  of  the  parent 

colony. 

Make  a  figure  of  a  parent  colony  that  incloses  several 

daughter  colonies  of  different  sizes. 

5.  Volvox  globator  is  monoecious.  Look  for  macro- 
gametes  and  bundles  of  microgametes. 

Figure  them. 

6.  Be  sure  to  recognize  the  significance  of  the  fact  that 
the  cells  of  Volvox  are  differentiated  into  somatic  and  germ 
cells,  and  to  understand  the  resulting  physiological  division 

of  labor. 

7.  Consider  the  reasons  for  and  against  regarding  Volvox 
and  allied  organisms  as  plants  rather  than  animals. 

Meyer:  Ueber  den  Bau  von  V.  aureus  and  V.  globator.    Bot.  Cent.,  63, 
1895. 

CERATIUM 

1.  Examine  this  form  with  a  high  power,  and  in  a  favor- 
able specimen  notice  the  sculptured  outer  surface  of  the 
cellulose  test.  The  living  animals  are  green  or  brown  owing 
to  the  presence  of  chromatophores  in  the  protoplasm. 

2.  Note  the  furrow  encircling  the  body.  Does  it  extend 
completely  around  it?  Is  there  a  short  furrow  on  one  side 
at  right  angles  to  the  first,  or  a  depression  of  considerable 
size?    Understand  the  position  of  the  fiagella. 

Draw  the  animal,  showing  the  points  observed. 

Look  for  examples  of  the  earlier  stages  of  division,  and 


CERATIUM,    NOCTILUCA  35 

of  later  stages,  which  appear  as  chains  of  fully  formed  in- 
dividuals attached  together. 

Kofoid:    Exuviation,  Autotomy,  and  Regeneration  in  Ceratium.    Univ. 

Calif,  Pub.  4,   1908. 
:    The  Free  Living  Unarmored  Dinoflagellates.    Mem.  Univ.  Calif. 

Pub,  vol.  5,  1921. 

NOCTILUCA 

If  living  specimens  are  not  to  be  had  for  study,  material 
preserved  in  alcohol,  after  suitable  fixation,  can  be  used. 
Specimens  are  best  examined  in  a  cell-slide  under  a  cover- 
glass. 

1.  Observe  the  nearly  globular  shape,  and  on  one  side  a 
groove  from  which  arises  a  large  fiagellum  or  "tentacle."  Is 
there  a  deep  groove  near  it?  At  the  bottom  of  this  groove 
it  is  possible  to  see  the  mouth  in  a  living  specimen.  An- 
other smaller  fiagellum  is  visible  in  living  specimens  inserted 
at  the  bottom  of  the  mouth,  but  in  preserving  the  organism 
it  is  usually  destroyed. 

2.  Note  the  appearance  of  the  preserved  protoplasm.  The 
endoylasm  appears  parenchymatous.  At  one  point  a  more 
compact  mass  is  seen,  from  which  strands  appear  to  radiate. 
This  has  been  found  to  contain  the  nucleus. 

Noctiluca    is    luminescent,    and    frequently    causes    very 
brilliant  displays. 
Make  a  drawing. 

Calkins:    Nuclear  Division  in  Noctiluca.    Jour.  Morph,  15,  1899. 
Kofoid:    Craspedotella.    Bull.  Mus,  Harvard,  46,  1905. 


PORIFERA 

Cells  not  differentiated  to  form  definite  organs.  Water 
admitted  through  surface  pores  and  ejected  through  an  os- 
culum  or  through  oscula. 

Class  1.  Calcarea. 

With  a  skeleton  composed  of  calcareous  spic- 
ules. 
Subclass  1.  Homocoela. 

With  the  gastric  layer  continuous  so  the  col- 
lar cells  line  the  whole  gastric  cavity.     (Leu- 
cosolenia.) 
Subclass  2.  Heterocoela. 

Gastric  layer  discontinuous.     Collar  cells  re- 
stricted to  the  flagellated  chambers.     (Sycon.) 
Class  2.  Hexactinellida. 

With    a   skeleton    composed    of   silicious    six- 
rayed  spicules. 
Order  1.  Lyssacina. 

Spicules  separate  or   becoming  united.      (Eu- 
plectella.) 
Order  2.  Dictyonina. 

Spicules  united  from  the  first  into  a  firm  frame- 
work.    (Eurete.) 
Class  3.  Demospongiae. 

Great  diversity  of  structure.    Dominant  forms 
of  today. 
Subclass  1.  Tetraxonida. 

Typically   with    four-rayed   spicules.     (Corti- 

cella.) 
Subclass  2.  Monaxonida. 

Simple,  usually  unbranched  spicules.     Spongin 

frequently  present.     (Cliona,  Suberites,  Chal- 

ina,  Spongilla.) 
Subclass  3.  Keratosa.  . 

Skeleton  of  spongin  fibers.     No  true  spicules. 

(Euspongia,  Aplysina.) 
Subclass  4.  Myxospongida. 

Without  skeleton.     (Oscarella.) 

36 


SYCON 


37 


Galtsoff:    The  Amoeboid  Movement  of  Dissociated  Sponge  Cells.    Biol. 

Bull.,  vol.  45,  1923;  Regeneration  of  Microciona  (2  papers)  Jour.  Exp. 

Zool.',  42,  1925. 
Lankester:  A  Treatise  on  Zoology,  Porifera,  and  Ccelenterata,  Pt.  2,  1900. 
Moore:    A  Practical  Method  of  Sponge  Culture.    Bull.  U.  S.  Bur.  Fish., 

28,  1908. 
:    The  Commercial  Sponges  and  the  Sponge  Fisheries.    Bull.  U.  S. 

Bur.  Fish.,  1908. 
Parker:    The  Reactions  of  Sponges  with  a  Consideration  of  the  Origin 

of  the  Nervous  System.    Jour.  Exp.  Zool.,  8,  1910. 

:    The  Elementary  Nervous  System,  1919. 

Wilson,  H.  V.:    On  Some  Phenomena  of  Coalescence  and  Regeneration 

in  Sponges.    Jour.  Exp.  Zool.,  5,  1907. 
:    Development  of  Sponges  from  Dissociated  Tissue  Cells.     Bull. 

U.  S.  Bur.  Fish.,  30,  1910. 

and  Penney:    The  Regeneration  of  Microciona  from  Dissociated 


Cells.     Jour.  Exp.  Zool.,  56,  1930. 

SYCON  (Grantia) 

This  form  is  quite  common  along  the  New  England  coast, 
where  it  occurs  attached  to  rocks,  seaweeds,  and  submerged 
woodwork  from  just  below  the  lowest  tide  mark  to  a  number 
of  fathoms  in  depth.  You  should  visit  an  old  wharf  where 
specimens  may  be  found,  and  study  their  relation  to  the 
forms  with  which  they  are  associated.  Specimens  will  be 
found  to  vary  considerably  in  size.  The  largest  sometimes 
reach  an  inch  in  length. 

1.  Examine  a  dry  specimen  and  notice  its  general  shape, 
manner  of  attachment,  and  osculum.  The  osculum  is  sur- 
rounded by  a  funnel  of  rather  long  spicules.  Distributed 
over  the  general  surface,  more  or  less  hidden  by  the  numerous 
spicules,  are  many  small  pores.  Their  presence  may  be 
demonstrated  more  satisfactorily  later. 

2.  Look  for  indications  of  budding.  If  your  specimen 
does  not  show  this,  examine  others. 

Make  an  enlarged  drawing  of  a  sponge. 
With  a  razor  or  sharp  scalpel  cut  a  dry  specimen  into 
halves,  with  a  stroke  from  base  to  osculum,  and  notice: 

3.  The  central  cavity  or  cloaca. 

4.  Many  apopyles,  the  inner  openings  of  tubes  that  are 


38  PORIFERA 

embedded  in  the  walls  of  the  sponge,  will  be  seen  opening 
into  the  cloaca.    Are  the  apopyles  arranged  in  any  order? 

5.  With  the  low  power  of  your  microscope  (with  the  light 
turned  off)  examine  the  cut  wall  and  find  that  it  is  traversed 
by  parallel  tubes.  Determine  that  these  tubes  are  of  two 
kinds. 

(a)  Regular,  nearly  cylindrical  tubes  that  open  into  the 
cloaca  through  the  apopyles  and  that  bear  tufts  of  spicules 
on  their  closed  ends,  at  the  surface  of  the  body.  These  are 
the  radial  canals.  It  is  frequently  hard  to  see  their  openings 
into  the  cloaca,  as  the  apopyles  are  narrow,  so  the  section 
only  occasionally  passes  through  them. 

(6)  Smaller  and  less  regular  tubes  that  open  on  the  outer 
surface  between  the  clusters  of  spicules,  and  do  not  open  into 
the  cloaca.  These  are  the  incurrent  canals.  In  life  there  are 
small  pores,  prosopyles,  that  open  from  the  incurrent  canals 
into  the  radial  canals.  These  openings  are  very  minute  and 
are  apparently  capable  of  being  closed.  They  are  never 
visible  in  dried  material. 

6.  Examine  thin,  transverse  sections  of  a  dry  sponge  and 
determine  the  positions  of  radial  and  incurrent  canals. 

Make  a  drawing  that  will  show  the  arrangement  of  the 
canals. 

7.  Examine  the  spicules  and  determine  their  positions  as 
regards  canals.  Boil  a  portion  of  a  sponge  in  caustic  potash 
until  only  the  spicules  remain  and  examine  the  spicules.  See 
if  more  than  one  kind  occurs. 

Draw  specimens  of  the  spicules. 

Living  and  Sectioned  Material 

1.  Place  a  living  sponge  in  a  watch  glass  of  sea  water, 
add  a  little  powdered  carmine,  and  examine  it  with  the  low 
power  of  your  microscope  for  currents  of  water.  See  if  par- 
ticles are  moving  in  a  definite  direction  near  the  general  sur- 
face and  near  the  osculum.    • 

2.  With  a  sharp  razor  cut  tangential  sections  of  the  wall, 


SYCON  39 

as  thin  as  possible,  mount  in  sea  water  under  a  cover,  and 
examine  with  a  low  power.  This  will  show  both  incurrent 
and  radial  canals  in  cross-section.  How  can  you  distinguish 
one  from  the  other?  In  a  favorable  place  look  for  moving 
fiagella.  Are  jiagella  in  all  of  the  canals?  In  favorable  situ- 
ations it  can  be  seen  that  the  cells  that  have  fiagella  possess 
collars  also.  (Collars  may  be  withdrawn  by  cells  so  they  pro- 
trude but  slightly.)  You  see  now  what  causes  the  current  of 
water.  Do  you  understand  how  a  sponge  feeds?  The  choan- 
ocytes  of  the  sponge  resemble  choanoflagellate  protozoons. 

Make  a  drawing  showing  the  arrangement  of  choanocytes. 

Examine  transverse  sections  of  a  specimen  that  has  been 
decalcified  and  stained. 

1.  The  cloacal  chamber  is  lined  by  a  pavement  of  epith- 
elium. 

2.  The  radial  canals  are  lined  by  more  conspicuous  cells, 
the  gastric  epithelium,  or  choanocytes. 

3.  The  incurrent  canals  and  the  outer  surface  of  the 
sponge  are  covered  with  flattened  cells,  the  dermal  epithelium. 

4.  In  a  part  of  the  section  where  a  considerable  area  of 
choanocytes  appears  in  surface  view,  look  for  the  prosopyles, 
through  which  the  water  passes  from  the .  incurrent  to  the 
radial  canals.     (They  may  not  be  found.) 

5.  Make  out  any  structures  you  can  in  the  area  lying  be- 
tween the  dermal  and  gastric  layers.  What  cells  are  found 
here? 

Make  a  drawing  of  several  adjacent  canals  to  show  the 
above  points  and  indicate  the  course  of  the  water  by  arroivs. 

6.  In  the  stained  sections,  look  for  single  ova  and  for 
spheres  containing  many  spermatozoa,  the  sperm  spheres. 
Look  also  for  segmenting  eggs,  which  are  frequently  to  be 
found.  The  ova  are  evidently  formed  by  growth  of  undiffer- 
entiated cells  that  lie  between  the  definite  cell  layers  and  are 
fertilized  while  still  lying  where  they  have  developed,  just 
within  the  choanocyte  layer.  Remaining  in  place,  they 
undergo  cleavage  and  develop  as  far  as  the  amphiblastula 


40  PORIFERA 

stage  (see  figures  in  the  textbooks).  They  then  break 
through  the  choanocyte  layer  into  the  radial  canals  and  pass 
out  with  the  current  of  water.  Living  specimens  are  fre- 
quently found  with  such  embryos  issuing  from  the  oscula  in 
the  outgoing  current  of  water.  The  sperm  spheres,  when  fully 
developed,  also  break  through  the  choanocyte  layer  and, 
separating  into  their  component  spermatozoa,  pass  out  with 
the  outgoing  water. 

Ova  and  sperm  are  formed  by  the  same  individual,  and 
the  animal  is  therefore  hermaphroditic,  but  the  products 
ripen  at  different  periods  and  are  seldom  both  present  in  an 
individual  at  the  same  time. 

If  the  time  allows,  draw  ova,  sperm  spheres,  segmenting 
eggs,  and  embryos. 

It  is  desirable  to  examine  specimens  of  Leucosolenia,  a 
still  simpler  sponge,  and  of  some  of  the  more  complicated 
forms,  like  commercial  sponges,  Spongilla,  Cliona,  and 
Chalina.  Why  is  more  than  a  single  osculum  desirable  in 
such  forms?  Understand  the  relation  of  the  internal  struc- 
ture of  the  complicated  forms  to  the  more  simple  forms. 
What  reason  is  there  for  the  complication? 

The  individual  cells  of  sponges  (Microciona)  may  be 
separated  by  squeezing  through  fine  silk  bolting  cloth.  Such 
cells  will  come  together  in  a  dish  of  sea  water  to  form  ag- 
gregates that  will  develop  into  new  sponges.  (See  Wilson 
and  Galtsoff,  loc.  cit.) 


COELENTERATA 

With  a  single  continuous  coelenteron  or  gastro-vascular 
cavity.  With  tentacles  and  nettle  cells.  With  two  cellular 
layers  and  a  mesoglea. 

Class  1.  Hydrozoa. 

Coelenteron  simple,  without  septa.  Gonads 
usually  ectodermal.  Fully  formed  medusae 
have  a  velum.     (Craspedote  medusae.) 

Order  1.  Leptolinae. 

With  a  fixed  zoophyte  stage. 
Suborder  1.  Anthomedusae.     (Gymnoblastea.) 

Without    hydrothecae    or    gonothecae.      The 
medusa    bears    gonads    on    the    manubrium. 
(Bougainvillia,    Eudendrium,    Clava,    Hydra, 
Hydractinia,  Pennaria,  Tubularia.) 
Suborder  2.  Leptomedusae.     (Calyptoblastea.) 

With  hydrothecae  and  gonothecae.  The 
medusa  bears  gonads  on  the  radial  canal. 
(Campanularia,  Gonionemus,  Obelia,  Sertu- 
laria,  Tima.) 

Order  2.  Trachylinae. 

Without  fixed  zoophyte  stage, 
Suborder  1.  Trachymedusae. 

Tentacles   from  the  margin  of  the  umbrella. 
Gonads  on  the  radial  canals.     (Petasus.) 
Suborder  2.  Narcomedusae. 

Tentacles  from  the  exumbrella.  Gonads  on  the 
manubrium.     (Aeginopsis.) 

Order  3.  Hydrocorallina. 

Massive  calcareous  exoskeleton.     (Millepora.) 

Order  4.  Siphonophora. 

Pelagic.    Colonial. ""  Colony  usually  shows  ex- 
treme polymorphism  of  its  zooids.     (Physalia.) 
Class  2.  Scyphozoa. 

Body  wall  of  polyp  thrown  into  four  ridges 
(Taenioles)  which  project  into  the  coelenteron. 
Medusa  generally  without  velum  and  with  gas- 
tric tentacles  (acraspedote  medusae).  Medu- 
soid  form  predominating. 

41 


42  COELENTERATA 

Order  1.  Stauromedusae. 

Conical  or  vase-shaped  umbrella.  No  ten- 
taculocysts.    (Lucernaria,  Tessera.) 

Order  2.  Peromedusae. 

Conical  umbrella  with  transverse  constriction. 
Four  interradial  tentaculocysts.      (Pericolpa.) 

Order  3.  Cubomedusae. 

Four-sided  umbrella.  With  perradial  tentacu- 
locysts.   Velum  present.     (Charybdea.) 

Order  4.  Discomedusae. 

Saucer-shaped  umbrella.  Perradial  and  inter- 
radial tentaculocysts.     (Aurelia,  Cyanea.) 

Class  3.  Actinozoa. 

With  a  stomodaeum,  and  with  mesenteries  ex- 
tending into  the  coelenteron.    Fixed  forms. 

Subclass  1.  Zoantharia. 

Mesenteries  and  tentacles  usually  very  numer- 
ous. 

Order  1.  Actiniaria. 

Usually  single.  No  skeleton.  (Metridium,  Sa- 
gartia.) 

Order  2.  Madreporaria. 

Usually  form  colonies  and  always  have  cal- 
careous exoskeleton.  (Astrangia,  Orbicella, 
Meandrina.) 

Order  3.  Antipatharia. 

Treelike.  Mesenteries  and  tentacles  compara- 
tively few.    Chitinoid  skeleton.     (Cirripathes.) 

Subclass  2.  Alcyonaria. 

Mesenteries  and  tentacles  eight  in  number. 
Tentacles  branched. 

Order  1.  Alcyonacea. 

Skeleton  in  the  form  of  small,  irregular  bodies, 
frequently  calcareous  spicules.  (Alcyonium, 
Tubipora.) 

Order  2.  Gorgonacea. 

Treelike,  with  calcareous  or  horny  exoskeleton. 
No  siphonoglyphes.     (Gorgonia.) 

Order  3.  Pennatulacea. 

Colony  with  one  end  usually  embedded  in  the 
sea   bottom.      (Pennatula,  Renilla.) 


HYDRA  43 

Hargitt,  C.  W.:    The  Anthozoa  of  the  Woods  Hole  Region.    Bull.  Bur. 

Fish.,  xxxii,  1912,  Doc.  No.  788. 
:    The  Medusas  of  the  Woods  Hole  Region.    Bull.  Bur.  Fish.,  xxiv, 

1904. 
Mayer:    Medusas  of  the  World.    Carnegie  Inst.,  Washington,  1910. 
Nutting:    The  Hydroids  of  the  Woods  Hole  Region.    Bull.  U.  S.  Fish. 

Com.,  19,  1899. 

HYDROZOA 

HYDRA  (Fresh-water  Polyp) 

Hydra,  the  common  fresh-water  coelenterate,  is  fre- 
quently found  in  quiet  pools  or  sluggish  streams  that  contain 
lily  pads,  decaying  leaves,  and  other  vegetable  matter.  The 
animals  may  frequently  be  found  by  examining  the  surfaces 
of  submerged  leaves,  but  it  is  usually  better  to  allow  such 
material  to  stand  in  glass  jars  for  a  day  or  two,  as  the  ani- 
mals then  tend  to  collect  on  the  lighter  sides  of  the  vessels. 
They  are  easily  kept  in  balanced  aquaria. 

Examine  specimens  in  an  aquarium  and  find  what  you  can 
about  their  mode  of  life.    Do  they  form  colonies? 

Place  a  specimen  in  a  watch  glass  of  water  and  examine 
it  with  a  lens. 

1.  What  is  its  shape  and  color?  Is  it  attached?  If  so,  by 
what  part  of  the  body?  Notice  the  circlet  of  tentacles.  How 
many  are  there?  Compare  notes  with  others  and  see  if  all 
have  the  same  number.    How  are  they  placed? 

2.  Does  the  Hydra  move  its  body  or  tentacles?  Is  it  sen- 
sitive? 

3.  Examine  with  a  low  power  of  the  microscope  and  re- 
view the  above  points.  You  may  also  be  able  to  see  the 
mouth  around  which  the  tentacles  are  arranged.  What  is  the 
shape  of  the  mouth  when  open? 

Make  two  drawings,  one  showing  the  animal  expanded 
and  the  other  contracted. 

Place  your  specimen  on  a  slide  under  a  coverglass  that  is 
supported  by  the  edge  of  another  coverglass  and  examine 
with  a  high  power.    Be  careful  not  to  crush  it.    Notice: 

4.  The  outer  layer,  ectoderm.     What  is  its  color?     Is  it 


44  COELENTERATA 

continuous  over  the  whole  outer  surface?  Does  it  vary  in 
thickness?  Are  the  cells  of  which  it  is  composed  apparently 
all  alike? 

5.  The  inner  layer,  endoderm.  What  is  its  color?  If 
color  is  present,  is  it  evenly  diffused  or  is  it  collected  in 
special  bodies?  Are  the  cells  of  which  the  endoderm  is  com- 
posed apparently  all  alike?  Do  they  differ  in  appearance 
from  those  of  the  ectoderm  other  than  in  color?  If  the  speci- 
men is  not  deeply  colored,  look  for  flagella  moving  in  the  in- 
ternal cavity. 

6.  Examine  the  ectoderm  of  the  tentacles  carefully  and 
notice  that  each  of  the  large,  rounded,  clear  bodies,  the  ne- 
matocysts,  shows  a  rather  indefinite  streak  (the  stinging 
thread)  running  from  its  outer  end,  back  into  the  interior. 
See  if  you  can  find  the  trigger  {cnidocil)  on  any  of  these  cells. 

Draw  a  portion  of  a  tentacle  showing  the  distribution  of 
the  nematocysts. 

7.  Place  your  specimen  under  the  low  power  of  the  micro- 
scope, carefully  run  in  a  drop  of  safranin,  and  see  if  any  of 
the  nematocysts  are  discharged  when  the  safranin  touches 
them.  Examine  with  a  high  power  and  notice  the  appear- 
ance of  the  thread.  Notice  the  change  in  the  shape  of  the 
nematocysts  that  have  discharged.  See  if  you  can  find  two 
kinds. 

Make  an  enlarged  drawing  of  an  exploded  nematocyst. 

8.  Examine  prepared  transverse  sections  of  Hydra.  Notice 
that  the  body  is  composed  of  two  layers  of  cells,  between 
which  is  an  almost  structureless  thin  layer.  Do  the  cells  of 
the  two  layers  differ  in  size,  shape,  and  structure?  Do  you 
find  more  than  one  kind  of  cell  in  each  or  either  of  these 
layers?    Where  are  they?    What  are  they? 

Make  a  careful  drawing  of  the  section  showing  the  ar- 
rangement as  you  see  it. 

Examine  longitudinal  sections,  for  differences  in  the  char- 
acter of  the  ectoderm  and  endoderm  in  different  parts  of  the 
body. 


HYDRA,    OBELIA  45 

9.  Reproduction.  Examine  living  specimens  in  a  watch 
glass  of  water  for  bud  formation  and  for  sexual  organs. 
Spermaries  are  just  beneath  the  tentacles;  ovaries,  lower 
down;  buds  may  be  found  at  different  levels.  What  cells  are 
involved  in  the  formation  of  each  of  these? 

Eggs  are  not  formed  at  all  seasons  of  the  year  and  vary 
greatly  in  appearance  according  to  their  stage  of  develop- 
ment. 

Make  drawings  of  the  stages  of  reproduction  that  you 
find. 

Tannreuther:    The  Development  of  Hydra.    Biol.  Bull.,  14,  1908. 
Whitney:    Artificial  Removal  of  the  Green  Bodies  from  Hydra  viridis. 
Biol.  Bull.,  14,  1908. 

OBELIA 

These  small,  colonial  animals  are  common  on  submerged 
or  floating  wood,  stones,  and  seaweeds,  where  the  water  is 
rather  free  from  sediments.  With  the  aid  of  a  glass-bottomed 
pail  they,  in  company  with  many  other  forms,  may  usually 
be  seen  about  old  wharfs. 

Note  the  appearance  of  large  colonies  of  this  form  that 
are  growing  on  stones  or  on  pieces  of  board  or  kelp. 

1.  Notice  the  treelike  form  of  any  single  stem.  Do  the 
branches  have  a  definite  size  and  arrangement? 

2.  At  the  extremities  of  the  branches  are  the  single  in- 
dividuals, hydranths  or  zooids.  Each  is  similar  to  a  single 
Hydra  in  certain  ways,  but  is  inclosed  in  a  vase-like  forma- 
tion, the  hydrotheca. 

3.  The  latter  is  a  continuation  of  a  tough,  membranous 
sheath,  the  perisarc,  which  covers  each  part  of  the  whole 
colony. 

Do  you  notice  any  modifications  of  the  perisarc  below  the 
hydrotheca?     Do  the  modifications  serve  any  purpose? 

4.  Trace  the  stem  to  the  creeping,  stolon-like  portion  of 
the  colony,  the  hydrorhiza. 

Make  a  drawing  of  a  colony. 


46  COELENTERATA 

5.  The  fleshy  continuation  of  the  zooid  down  into  the 
stalk  is  termed  the  coenosarc.  Is  it  in  close  contact  with  the 
perisarc? 

6.  In  an  expanded  hydranth,  note  the  mouth,  the  arrange- 
ment of  the  tentacles,  and  the  number  of  tentacles.  How  is 
the  individual  supported  in  the  hydrotheca?  Trace  the 
coelenteric  cavity  through  branches  and  hydranths  and  de- 
termine whether  it  is  continuous. 

7.  Can  you  determine  what  keeps  the  fluid  in  the  cavity 
in  motion? 

8.  Examine  a  hydranth  with  a  high  power  and  look  for 
the  cell  layers  characteristic  of  coelenterates.  Determine  how 
its  tentacles  differ  from  the  tentacles  of  Hydra,  and  explode 
nematocysts  as  in  Hydra. 

Make  a  drawing  of  a  hydranth. 

9.  Look  for  certain  extremities  which  show  neither  ten- 
tacles nor  any  opening  in  the  outer  covering.  Such  a  con- 
dition signifies  either  an  immature  hydranth  or  a  reproductive 
individual.  If  the  latter,  it  is  considerably  swollen  and  is 
termed  a  gonosome.  The  central  core  of  a  gonosome,  the 
blastostyle,  should  be  examined  for  gonophores,  frequently 
called  medusa  buds.  This  may  require  a  high  power.  De- 
termine how  the  gonophores  are  arranged  around  the  blas- 
tostyle. Are  all  in  equal  stages  of  development?  What 
relation  has  the  end  of  the  blastostyle  to  the  outer  covering, 
the  gonangiumf 

Make  a  drawing  of  a  gonosome. 

10.  The  free  medusae  are  small,  transparent,  and  easily 
overlooked.  During  the  breeding  season  they  may  usually  be 
found  in  abundance  in  dishes  in  which  colonies  have  been 
kept  over  night.  Notice  their  movements  and  their  positions 
while  at  rest  on  the  bottom.  The  number  of  tentacles  and 
the  position  of  the  sense  organs  is  definite  for  the  species. 
Two  species  that  differ  in  the  number  of  tentacles  are  com- 
mon at  Woods  Hole.  The  inverted  bell  with  the  manubrium 
sticking  out  from  the  convex  surface  of  the  resting  specimen 


OBELIA,    CAMPANULARIA  47 

is  characteristic  for  this  form.  Notice  the  quick  reversal 
when  the  animal  swims.  The  radial  canals  are  easily  seen, 
but  the  gonads  are  not  developed  at  the  time  of  liberation. 
The  velum  is  very  small. 

Gonionemus  is  a  more  favorable  medusa  to  study.  This 
form  is  valuable  for  comparison. 

CAMPANULARIA 

In  structure  and  habits  this  form  is  so  much  like  Obelia 
that  it  is  not  easy  to  distinguish  the  two  genera  without 
studying  the  gonosomes.  Several  species  are  found  at  Woods 
Hole,  two  of  which  (C ' ampanularia  flexuosa  and  C.  calceo- 
lifera)  are  usually  abundant  during  the  summer. 

The  gonosome  of  one  species  superficially  looks  like  the 
gonosome  of  Obelia,  while  the  other  has  a  notch  on  one  side 
near  its  extremity.    In  structure  they  are  similar. 

The  blastostyle  runs  throughout  the  length  of  the  gonan- 
gium  and  gives  rise  to  buds  that  develop  into  imperfect  gono- 
phores.  The  structure  of  these  gonophores  is  difficult  to  make 
out  in  fresh  material.  While  they  are  comparable  to 
medusae,  they  never  become  detached,  and  organs  usually 
present  are  largely  aborted. 

The  distinct  manubrium  of  the  male  gonophore  becomes 
charged  with  sperm  which,  as  they  develop,  press  the  ecto- 
derm of  the  manubrium  against  the  ectoderm  of  the  sub- 
umbrella.  Ultimately  the  ectoderm  of  the  manubrium 
ruptures  and  the  sperm  escapes  through  the  subumbrellar 
cavity. 

A  female  gonophore  ripens  usually  one,  sometimes  two, 
eggs.  The  mature  egg,  which  lies -inside  the  ectoderm  of  the 
manubrium,  before  segmentation  is  flattened  and  molded  be- 
tween the  mass  of  the  manubrium  and  the  subumbrellar 
wall.  The  growth  of  the  egg  presses  the  manubrium  to  one 
side.  Such  an  egg  appears  as  a  brownish  granular  mass  with 
a  distinct,  clear  nucleus.  The  ectoderm  of  the  manubrium 
ultimately  ruptures  and  liberates  the  eggs  into  the  subum- 


48  COELENTERATA 

brellar  cavity.  Cleavage  stages  are  frequently  found,  and 
planulae,  the  larval  stage  that  is  finally  set  free,  may  be 
found.  In  old  gonosomes,  where  most  of  the  gonophores  have 
matured  their  sexual  products  and  the  outer  end  of  the  blas- 
tostyle  has  broken  down,  especially  large  planulae  may  fre- 
quently be  found.  These  may  be  liberated  with  needles  and 
studied  with  a  high  power  for  cilia  and  the  arrangement  of 
cells.  Older  planulae  will  show  a  streak  that  indicates  the 
formation  of  a  cavity  inside. 

Planulae  of  this  kind  placed  in  a  watch  glass  of  sea  water 
and  covered  to  prevent  evaporation  will  soon  attach  and  de- 
velop into  hydranths.  When  attached  the  sea  water  should 
be  changed  twice  a  day.  Without  feeding,  development  is  not 
continued  far. 

Make  drawings  of  gonosomes  and  of  a  planula. 

SERTULARIA 

In  habits  and  relation  of  parts  there  is  nothing  funda- 
mentally different  from  the  other  forms  studied.  The  gon- 
osomes present  another  modification. 

1.  The  male  gonosome  has  the  blastostyle  pressed  to  one 
side  and  carries  a  single  gonophore  with  prominent  manu- 
brium and  a  mass  of  sperm.  The  sperm  are  actually  be- 
tween the  ectoderm  and  endoderm  of  the  manubrium. 

2.  The  female  gonosome  has  the  blastostyle  pressed  to  one 
side  and  from  it  originates,  one  at  a  time,  vestigial  gono- 
phores that  in  turn  push  toward  the  distal  end  of  the  gonan- 
gium  and  discharge  their  eggs  into  a  specially  constructed 
brood  pouch,  the  acrocyst.  By  opening  acrocysts  with 
needles  stages  in  development  up  to  planulae  may  be  ob- 
tained. 

Make  a  drawing  showing  a  female  gonosome  with  an  acro- 
cyst. 

GONIONEMUS 

This  form,  belonging  to  the  suborder  Leptomedusae,  has 
a  much  reduced  polyp  generation.    It  is  found  in  considerable 


SERTULARIA,    GONIONEMTJS  49 

numbers  throughout  the  summer  in  the  border  of  eel  grass  in 
the  Eel  Pond  at  Woods  Hole,  where  it  may  be  obtained  with 
a  dip-net.  It  is  more  satisfactory  to  study  than  the  medusa 
of  Obelia,  as  it  is  much  larger  and  its  movements  and  organs 
are  more  easily  observed.  In  plan  of  structure  the  two  are 
quite  similar. 

Put  a  living  specimen  in  a  jar  containing  sea  water,  or  in 
a  finger  bowl,  with  a  black  tile  beneath,  and  notice: 

1.  Its  method  of  locomotion.  To  the  contraction  of  what 
part  of  the  bell  is  movement  due?  How  large  is  the  jet  of 
water  that  is  delivered  from  the  bell?  Why  is  the  jet  made 
narrow?  Does  the  jet  necessarily  leave  at  the  center  or  may 
it  be  thrown  from  one  side?  Should  it  be  thrown  from  one 
side,  what  would  be  the  result? 

2.  Its  position  in  the  water  when  quiet.  Why  is  this  po- 
sition more  desirable  than  the  opposite?  With  a  needle  point 
prove  that  various  parts  of  the  body  are  sensitive. 

With  either  fresh  or  preserved  material,  notice: 

1.  Its  flattened  dome  shape.  The  convex  face  is  called 
the  exumbrella  (aboral),  while  the  concave  portion  is  termed 
the  subumbrella  (oral) . 

2.  The  velum  is  the  perforated  diaphragm  that  partly 
closes  in  the  subumbrella.  All  medusae  possessing  this 
structure  are  classed  as  Craspedota.  Do  you  understand  its 
use? 

3.  In  the  center  of  the  subumbrella  is  seen  the  large  pen- 
dent manubrium,  at  the  extremity  of  which  is  a  wide-lipped 
mouth.  What  is  the  shape  of  the  mouth  when  open?  How 
does  it  compare  in  this  respect  with  the  mouth  of  Hydra?  If 
the  medusa  is  alive,  feed  it  with  small  bits  of  clam  meat. 

4.  From  the  capacious  sac  at  the  base  of  the  cavity  of  the 
manubrium,  the  stomach,  the  four  radial  canals  lead  to  the 
periphery  of  the  disk,  where  they  open  into  the  very  delicate 
circular  canal.  The  four  radii  marked  out  by  these  canals 
are  called  the  perradii.  Do  you  understand  the  use  of  these 
canals? 

4 


50  COELENTERATA 

5.  The  gonads  hang  from  beneath  the  radial  canals  into 
the  subumbrellar  space.  They  are  lobulated  in  structure, 
and  more  or  less  prominent  according  to  maturity  and  the 
breeding  season.  The  eggs  or  spermatozoa,  as  the  case  may 
be,  are  dehisced  from  these  into  the  water  directly. 

During  the  breeding  season  specimens  placed  in  the  dark 
in  the  latter  part  of  the  afternoon  and  left  for  two  or  three 
hours  will  shed  eggs  and  sperm.  The  fertilized  egg  under- 
goes cleavage,  a  planula  is  formed  that  finally  attaches  at 
one  end  and  develops  into  the  hydra  stage.  Eggs  are  nor- 
mally laid  about  8  p.  m. 

6.  The  tentacles.  Is  their  arrangement  a  radially  sym- 
metrical one?  How  are  the  nematocysts  arranged  on  them? 
Look  for  adhesive  organs  on  them.     Of  what  use  are  such 

organs? 

Turn  your  specimen  with  the  velum  side  toward  you  and 
study  the  edge  of  the  medusa  with  a  low-power  objective  for 
the  sense  organs.    These  are  of  two  kinds: 

(a)  The  larger,  round  bodies  at  the  bases  of  the  tentacles 
communicate  with  the  circular  canal  (which  may  possibly  be 
seen  along  the  edge  of  the  bell) .  They  are  filled  with  a  layer 
of  strongly  pigmented  endoderm  cells  and  are  probably  light- 
percipient  organs. 

{b)  Other  small  sessile  and  transparent  outgrowths,  situ- 
ated between  the  bases  of  the  tentacles,  are  the  so-called 
statocysts  (lithocysts) ,  which  are  probably  static  organs. 

All  of  the  tentacles  are  abundantly  supplied  with  tactile, 
sensory  cells.  There  is  a  well-established  circumvelar  nerve 
ring  (not  easily  determined  in  living  material)  derived  from 
the  ectoderm,  also  scattering  nerve  cells  beneath  the  ecto- 
derm in  connection  with  the  muscular  tissue.  Exumbrellar 
and  subumbrellar  layers  of  muscle  fibers  are  also  present. 

Make  a  drawing  from  the  side,  slightly  tipped,  to  show 
the  velum,  and  another  as  seen  from  the  oral  surface. 

Brooks:    Life  History  of  Hydromedusae.    Mem.  Bost.  Soc.  Nat.  Hist.,  3, 
1886. 


GONIONEMUS,   TUBULARIA  51 

Murbach:  The  Static  Function  in  Gonionemus.  Am.  Jour.  Physiol., 
10,  1903. 

Perkins:  The  Development  of  Gonionema  murbachii.  Proc.  Acad.  Nat. 
Sci.,  Phila.,  1902. 

:    Gonionemus,  Science,  1926,  p.  93. 

Yerkes:  A  Study  of  the  Reaction  of  the  Medusa  Gonionema  mur- 
bachii to  Photic  Stimuli.    Am.  Jour.  Physiol.,  9,  1903. 

TUBULARIA  (Parypha) 

This  form  is  frequently  abundant  on  the  piles  of  old 
wharfs  and  on  rocks,  where  the  colored  colonies  form  con- 
spicuous masses  just  below  low-water  mark. 

Examine  the  general  form  of  a  colony  and  note,  either 
with  a  hand  lens  or  with  the  naked  eye,  the  stem,  or  hydro- 
caulus,  as  it  arises  from  the  branching,  matted  hydrorhizal 
portion  of  the  colony.  The  parts  of  the  colony  will  be  seen 
to  differ  from  the  Leptomedusan  (Campanularian)  form 
studied,  especially  in  branching,  rigidity,  hydrothecae,  and 
gonosomes. 

Make  a  drawing  to  show  the  formation  of  the  colony. 

1.  How  does  a  hydranth  differ  from  the  hydranth  of 
Obelia  in  the  matter  of  tentacles?    Is  a  hydrotheca  present? 

2.  The  mouth  is  terminal  and  is  situated  at  the  end  of  a 
proboscis. 

3.  The  short  but  rather  large  body  of  the  hydranth  passes 
back  to  the  perisarc  as  the  fleshy  axis,  coenosarc. 

4.  Notice  the  gonosomes  between  the  rows  of  tentacles. 
What  is  their  origin  and  arrangement?  This  is  a  form  in 
which  the  medusae  are  not  set  free,  but  remain  vestigial. 
They  show  neither  radiating  nor  circular  canals.  The  gonads 
ripen  on  the  partially  developed  manubrium  of  the  medusa. 
The  sexes  are  separate. 

Make  a  drawing  of  a  hydranth. 

5.  The  male  gonophores  when  nearly  mature  are  rounded 
or  elongated  with  the  space  apparently  between  the  man- 
ubrium and  subumbrellar  surface  filled  with  sperm.  In  fact, 
the  sperm  are  enclosed  between  the  ectoderm  and  endoderm 
of  the  manubrium,  but  the  ectoderm  is  pressed  over  against 


52  COELENTERATA 

the  ectoderm  of  the  subumbrella  so  that  this  space  is  practi- 
cally obliterated.  These  sperm  become  active  when  liberated 
in  sea  water. 

6.  The  female  gonophore  when  mature  is  more  elongated, 
shows  indications  of  tentacles  at  the  free  extremity,  and  there 
is  an  actual  subumbrellar  space.  The  eggs  are  formed  in 
the  ectoderm  of  the  manubrium  and  are  shed  into  the  sub- 
umbrellar cavity.  An  egg  develops  into  a  larva  called  an 
actinula.  With  needles  open  a  female  gonophore  and  ex- 
amine the  developmental  stages.  These  are:  (a)  somewhat 
irregular  disk-shaped  embryos  with  a  variable  number  of  pro- 
jections (the  forming  tentacles)  around  the  margin,  (b) 
Older  stages  with  the  tentacles  more  developed  and  with  disk- 
or  lens-shaped  bodies  in  which  the  coelenteric  cavity  can  be 
easily  seen,  (c)  Actinula  stage.  Essentially  a  small  polyp. 
Notice  the  number  of  tentacles,  the  position  of  the  mouth, 
and  the  method  of  locomotion. 

Actinulae  kept  in  a  covered  watch  glass  of  sea  water  will 
attach  and  form  the  basis  of  new  colonies. 

Make  drawings  of  gonosomes,  gonangia,  and  developmen- 
tal stages. 

7.  The  arrangement  of  the  attached  medusae  is  best  seen 
in  sections. 

Sections  show  the  same  body  layers  as  Hydra,  and  the 
derivation  of  the  medusa  as  an  outpocketing  of  the  wall  of 
the  hydranth  is  evident. 

Hargitt:    The  Early  Development  of  Pennaria  tiarella.    Arch.  f.  Ent- 

wicklungsmech.,  18,  1904. 
Pearse:    Reactions  of  Tubularia  crocea.    Am.  Nat.,  40,  1906. 
Torrey:     Biological  Studies   on  Corymorpha.     I.   Jour.   Exp.   Zool.,   1, 

1904;  II.  Univ.  Calif.  Pub.  Zool.,  3,  1907. 

BOUGAINVTLLIA 

This  form  is  not  always  obtainable  during  the  summer 
months.  It  occurs  in  fair  abundance  at  Woods  Hole  earlier  in 
the  season,  attached  to  piles  and  floating  timbers. 


BOUGAINVILLIA,    HYDRACTINIA  53 

1.  Examine  the  colony  for  arrangement  of  branches,  and 
determine  the  relation  of  perisarc  and  coenosarc. 

2.  How  do  the  hydranths  differ  from  those  of  Obelia?  Is 
the  number  of  tentacles  constant?  Is  the  hydranth  as  con- 
tractile as  it  is  in  Obelia? 

3.  Look  for  gonosomes.  The  gonophores  are  borne  singly 
or  in  clusters  on  the  main  stem  and  branches.  By  examining 
a  number  of  buds  the  general  method  of  medusa  formation  can 
be  determined.  If  possible,  find:  (a)  a  young  bud  slightly 
swollen  showing  the  thin  perisarc  with  the  cellular  layers  in- 
side and  a  somewhat  enlarged  coelenteron.  {b)  A  bud  show- 
ing a  thickening  of  the  ectoderm  at  the  distal  end,  in  which  a 
cavity  appears,  the  subumbrellar  cavity,  (c)  A  bud  showing 
the  formation  of  the  manubrium  as  a  projection  into  this 
cavity.  The  manubrium  involves  both  layers,  as  the  sub- 
umbrellar cavity  is  wholly  ectodermal.  The  ectodermal  distal 
covering  of  the  subumbrellar  cavity  will  later  perforate  and 
form  the  velum,  (d)  A  bud  showing  the  perforated  velum 
and  the  tentacles.  The  tentacles  are  at  first  directed  through 
the  opening  of  the  velum  into  the  subumbrellar  cavity. 

4.  Find  medusae  that  have  become  detached.  Notice  the 
arrangement  and  number  of  tentacles,  the  eye  spots  at  the 
bases  of  the  tentacles,  the  radial  and  circular  canals,  and  the 
mouth  appendages.  Gonads  are  not  developed  at  the  time  of 
liberation.     Study  the  swimming  movements. 

Make  drawings  to  illustrate  development  and  adult  struc- 
ture of  medusae. 

HYDRACTINIA 

This  form  is  particularly  abundant  at  Woods  Hole  on  the 
shells  of  gastropods  inhabited  by  hermit  crabs,  but  at  certain 
seasons  is  abundant  on  rocks  or  pebbles  and  sometimes  on 
piles. 

1.  Examine  a  shell  covered  with  a  colony,  and  notice  the 
distribution  and  size  of  the  individuals. 

2.  Notice  the  hard  secretion  that  sticks  up  as  prominent 
points  and  ridges  between  the  individuals. 


54  COELENTERATA 

3.  Break  a  shell  and  place  the  fragments  incrusted  side  up 
in  a  watch  glass  of  sea  water  and  examine  with  a  low  power. 
Three  kinds  of  individuals  will  be  apparent:  (a)  large  indi- 
viduals with  long  tentacles.  These  are  the  feeding  hydranths. 
They  differ  somewhat  in  appearance  in  the  male  and  female 
colony.  The  male  individual  has  a  large  proboscis,  while  the 
female  individual  has  only  a  slightly  arched  disk  with  the 
mouth  in  the  center,  (b)  Reproductive  individuals  with 
knoblike  tentacles,  a  proboscis  that  is  usually  retracted,  a 
mouth,  and  with  gonophores  along  their  sides.  In  female 
gonophores  the  manubrium  and  a  number  of  eggs  may  be 
seen.  These  gonophores  never  become  detached  and  never 
show  further  medusoid  structure,  (c)  Elongated  individuals, 
especially  near  the  outskirts  of  the  colony,  that  have  rounded 
tentacles,  proboscis,  and  mouth  like  those  of  the  reproductive 
individuals.  These  sometimes  branch  and  have  a  habit  of 
bending  the  head  toward  the  base  or  even  twisting  the  body 
into  a  spiral.  They  are  not  distinguishable  from  the  repro- 
ductive individual  except  by  shape  and  the  fact  that  they 
have  no  gonophores. 

4.  Notice  that  the  individuals  are  connected  at  the  bases 
by  a  fleshy  layer  which  is  responsible  for  the  deposit  already 
mentioned. 

Make  a  drawing  of  each  kind  of  individual. 

HYDROCORALLINA 

To  this  group  belong  forms  that  have  heavy  calcareous 
exoskeletons.  While  material  is  generally  not  at  hand  to 
study  the  polyps,  it  is  desirable  to  study  and  sketch  the  char- 
acteristic forms  of  colonies  such  as  Millepora  and  Stylaster, 
and  to  note  the  difference  in  the  distribution  of  pores.  Later 
you  will  see  how  decidedly  these  differ  from  the  ordinary 
stony  corals. 

SIPHONOPHORA 

Examine  living  or  preserved  specimens  of  Physalia,  and 
sketch  the  type  with  reference  to  showing,  if  possible,  the 


PHYSALIA,    AURELIA  55 

following  structures:  (a)  pneumatophore,  {b)  dactylozooids, 
(c)  gastrozooids,  (d)  gonodendrons,  (e)  tentacles.  It  will  be 
well  to  refer  to  a  textbook  to  find  the  positions  and  functions 
of  each  of  these. 

Bigelow:    The  Siphonophorae.     Mem.  Mus.  Comp.  Zool.,  Harvard,  38, 
1911. 

SCYPHOZOA 

AURELIA 

This  form  is  one  of  the  common  jellyfishes,  and  is  found 
floating  freely  in  the  water.  It  is  frequently  washed  up  on 
shore.  To  be  appreciated  these  medusae  should  be  seen  as 
they  occur  at  the  surface  of  the  sea,  before  they  have  been 
handled  or  injured.  Frequently  vast  numbers  may  be  seen 
together,  all  gently  pulsating  and  thus  keeping  near  the  sur- 
face. The  movement  is  very  different  from  that  of  most 
hydrozoan  medusae,  being  very  deliberate  and  graceful. 

If  living  material  is  offered,  study  the  method  of  locomo- 
tion and  compare  it  with  the  locomotion  of  Gonionemus. 
Like  the  latter,  the  discoid  animal  exumbrellar  (aboral)  and 
subumbrellar  (oral)  surfaces,  but  the  edges  of  the  disk  are 
indented,  fringed  with  very  numerous  short  tentacles,  and  a 
velum  is  wanting.  What  difference  does  the  velum  make  in 
locomotion? 

The  exumbrellar  surface  presents  little  of  interest.  In  the 
live  specimens,  however,  you  should  prove  that  the  animal  is 
sensitive  over  this  area  as  elsewhere. 

Preserved  and  hardened  material  is  better  than  living  for 
the  study  of  the  rest  of  the  anatomy  of  this  form.  With  a 
specimen  in  water  in  a  finger  bowl,  with  a  black  tile  for  the 
background,  find  the  following  from  the  subumbrellar  sur- 
face: 

1.  The  shape  of  the  animal.  Is  the  margin  perfectly 
circular  or  regularly  indented?  Are  all  of  the  marginal  por- 
tions similar? 

2.  Four  large,  fringed  oral  arms  or  lips  hang  from  the 


56  COELENTERATA 

corners  of  the  nearly  square  mouth,  which  is  located  in  the 
center.  Notice  how  each  arm  is  similar  to  a  long,  narrow 
leaf,  with  the  sides  folded,  especially  along  their  margins. 
Examine  the  arms  for  nematocysts.  Do  you  understand  how 
the  animal  gets  its  food?  If  the  arm  edges  appear  to  be 
covered  with  dark  specks  and  granules,  examine  to  see  if 
embryos  are  entangled  there. 

3.  The  mouth  is  found  to  lead  by  a  short  gullet  into  a 
rather  spacious  stomach,  which  is  produced  in  the  region  be- 
tween adjacent  corners  of  the  mouth  to  form  a  gastric  pouch. 
In  each  of  the  pouches  are  a  number  of  gastric  filaments. 
Determine  the  shape  of  the  stomach. 

4.  The  remaining  parts  of  the  digestive  (and  also  in  this 
case  circulatory)  system  include  the  numerous  radial  canals 
and  the  single  circular  canal. 

(a)  Directly  beneath  each  oral  arm  a  perradial  canal  is 
given  off,  which,  at  a  short  distance  from  the  stomach,  gives 
off  a  branch  on  either  side.  One  portion  of  the  perradial 
canal  continues  straight  to  the  margin  and  joins  the  circular 
canal,  without  further  subdivision,  but  the  two  side  branches 
in  turn  subdivide  several  times. 

(b)  From  the  peripheral  wall  of  each  gastric  pouch  three 
canals  pass  toward  the  margin;  the  middle  one  {interradial 
canal)  branches  somewhat  after  the  manner  of  the  perradial 
canals,  but  the  other  two  (adradial  canals)  continue  to  the 
circular  canal  without  further  branching.1 

5.  The  position  of  the  gastric  pouches  is  made  clearly 
manifest  by  the  gonads,  which  lie  on  the  floor  of  the  pouches, 
as  frill-like  structures,  horseshoe-shaped,  with  their  open 
sides  toward  the  mouth.  The  ova  or  spermatozoa  are  shed 
into  the  stomach  and  pass  out  of  the  mouth.  Embryos  in 
various  stages  of  development  may  frequently  be  found  ad- 
hering to  the  oral  arms.    The  sexes  are  separate.    On  the  sub- 

1  In  most  cases  the  foregoing  canals  are  very  evident,  but  if  they 
are  not,  they  may  be  injected  with  water  in  which  powdered  carmine 
is  mixed,  by  inserting  a  large-mouthed  pipette  into  the  stomach. 


AURELIA  57 

umbrellar  surface,  opposite  each  gonad,  is  a  little  pocket,  the 
sub  genital  pit,  which  opens  freely  to  the  outside.  Whatever 
purpose  this  may  serve,  it  does  not  function  to  conduct  the 
genital  products  to  the  outside. 

6.  Parallel  with  the  inner  or  concave  border  of  each  gonad 
is  a  row  of  delicate  gastric  filaments.  These  are  supplied 
with  nematocysts,  and  they  may  aid  in  killing  live  food  taken 
into  the  stomach.  These  structures  are  not  present  in  the 
Hydromedusa. 

7.  At  the  marginal  extremity  of  each  perradial  and  inter- 
radial  canal  there  is  an  incision,  on  the  edge  of  the  animal,  in 
which  there  are  sensory  organs.    In  each  incision  find: 

(a)  A  tentaculocyst  in  the  form  of  a  short,  clublike  struc- 
ture containing  a  prolongation  of  the  radial  canal.  At  its 
outer  extremity  are  calcareous  concretions  or  lithites,  and  a 
pigment  spot  or  ocellus.  Each  tentaculocyst  is  covered  abor- 
ally  by  a  hoodlike  projection,  and  on  the  sides  by  marginal 
lappets. 

(b)  Two  depressions,  one  above  and  the  other  below  the  ten- 
taculocyst. These  have  been  assigned  olfactory  functions,  and 
are  called  the  olfactory  pits.    Evidence  of  function  is  lacking. 

Make  a  drawing  showing  the  profile  of  the  entire  animal, 
and  show  the  structure  of  at  least  one  quadrant,  as  seen  from 
the  oral  surface. 

8.  If  time  permits,  study  developmental  stages. 

The  eggs  are  shed  through  the  mouth  and  frequently  be- 
come entangled  in  the  oral  arms,  where  they  may  develop 
into  planulae.  Most  of  the  eggs  are  set  free  in  the  water, 
where  they  develop. 

The  planula  after  swimming  for  some  time  attaches  by 
one  end,  acquires  a  coelenteron,  mouth,  and  tentacles.  Longi- 
tudinal ridges  called  taeniolae  or  taenioles  are  formed  in  the 
coelenteron,  septal  funnels  are  formed  between  the  tentacles 
and  mouth,  and  from  the  septal  funnels  ectoderm  cells  are 
budded  off  that  form  the  four  longitudinal  septal  muscles. 
This  larva  is  called  a  scyphistoma. 


58  COELENTERATA 

The  scyphistoma  grows,  acquires  more  tentacles,  may  bud 
to  form  other  scyphistomae,  and  usually  acquires  stolons, 
which  grow  out  from  the  body  wall  just  above  the  base. 
From  the  stolons  new  scyphistomae  arise.  Subgenital  pits 
make  their  appearance  in  the  position  formally  occupied  by 
the  septal  funnels,  and  an  ostium  appears  in  each  taeniole 
near  the  oral  surface.  In  this  way  a  ring  sinus  is  formed. 
Gastric  filaments  are  formed  on  the  edges  of  the  taenioles. 

From  the  oral  side  of  the  first  eight  tentacles,  sense  organs 
bud  out.  Eight  lobes  make  their  appearance  opposite  these 
sense  organs,  each  lobe  divides  into  two  lappets,  between 
which  the  sense  organ  lies.  While  these  changes  are  taking 
place  constrictions  running  around  the  body  appear  and 
deepen  so  the  body  is  divided  into  a  series  of  plates,  each 
of  which  has  eight  lobes,  eight  sense  organs,  and  sixteen 
marginal  lappets.  The  disk  at  the  free  extremity  is  the  oldest 
and  most  differentiated. 

This  stage  is  frequently  called  the  strobila,  but  there  is  no 
definite  dividing  line  between  scyphistoma  and  strobila.  The 
number  of  disks  formed  by  a  strobila  seems  to  be  dependent 
upon  conditions,  probably  largely  food  supply. 

Before  the  disks  are  ready  to  be  detached  as  ephyrae  the 
tentacles  disappear.  Ephyrae  are  detached  one  at  a  time 
from  the  free  end  as  they  mature. 

Up  to  this  point  students  will  be  able  to  determine  only 
part  of  the  points  mentioned  unless  an  abundance  of  material 
and  sections  are  provided.  The  remaining  points  are  easily 
determined. 

Examine  a  free  ephyra.  If  it  is  alive,  watch  it  swim.  Find 
the  mouth,  stomach,  marginal  lobes,  marginal  lappets,  and 
sense  organs.  Use  these  as  landmarks  to  determine  the  rela- 
tion of  parts  to  the  adult.  Are  there  any  outgrowths  from  the 
stomach?  Do  the  sense  organs  have  any  relation  to  branches 
from  the  stomach?     Can  you  find  gastric  filaments? 

From  the  shape  of  the  mouth  determine  which  of  the  lobes 
are  perradial  and  which  interradial.  What  part  of  the  adult 
is  represented  by  the  notches  between  the  lobes? 


AURELIA,   METRIDIUM  59 

Study  a  somewhat  older  ephyra  and  find  the  starting  of 
the  adradial  canals  and  the  beginning  of  the  formation  of 
adradial  cushions.  Examine  a  series  of  older  stages  and  find 
how  the  adradial  cushions  expand,  how  the  canals  branch, 
and  how  the  circular  canal  is  formed. 

Make  drawings  of  the  stages. 

By  way  of  comparison,  examine  demonstrations  of  Cyanea, 
Dactylometra,  Lucernaria,  or  other  forms  belonging  to  this 
group. 

Hargitt:    Variations  among  Scyphomedusae.    Jour.  Exp.  ZooL,  11,  1905. 

Hargitt,  C.  W.  and  G.  T.:    Studies  in  the  Development   of  Scypho- 
medusae.    Jour.  Morph.,  21,  1910. 

Mayer:    Rhythmical   Pulsation  in  Scyphomedusae.     Carnegie   Inst,   of 
Washington,  1906. 

ACTINOZOA 

METRIDIUM  (Sea-anemone) 

Specimens  are  quite  common  on  piles,  as  well  as  on  rocky 
bottoms,  and  may  be  easily  observed  by  means  of  a  glass- 
bottomed  pail.  Most  of  the  observations  can  be  made  much 
better  on  specimens  in  aquaria,  but  it  is  desirable  to  see  their 
natural  surroundings. 

Specimens  for  laboratory  study  should  be  placed  in 
aquaria,  and  left  undisturbed  until  they  are  fully  expanded. 
In  experimenting  be  very  careful  not  to  overstimulate. 

1.  Notice  the  shape  and  attachment  of  expanded,  living 
specimens  in  an  aquarium,  or  in  a  deep  finger  bowl.  The  free 
end,  called  the  disk  or  peristome,  is  fringed  with  tentacles, 
and  the  elongated  mouth  is  located  in  the  middle  of  this  area. 
At  one  or  both  angles  of  the  mouth  the  lips  are  thickened 
into  what  is  called  a  siphonoglyph. 

Make  a  drawing  of  the  animal. 

2.  Drop  a  few  grains  of  sand  on  the  tentacles.  Observe 
and  record  what  happens.  Repeat,  placing  the  sand  on  the 
oral  lips,  the  siphonoglyph,  and  the  oral  disk  successively. 
Try  the  same  using  sawdust  soaked  in  clam  juice.  Repeat, 
using  clam  meat. 


60  COELENTERATA 

What  conclusions  can  you  make:  first,  as  to  the  ability 
to  distinguish  food;  second,  as  to  methods  of  obtaining  food; 
and  third,  in  regard  to  ciliary  action? 

3.  Stimulate  the  animal  with  a  needle  at  various  points 
and  try  to  determine  where  it  is  most  sensitive.  Observe  its 
manner  of  contraction.  When  fully  contracted,  if  the  irrita- 
tion is  continued,  threadlike  structures,  acontia,  are  thrust 
out  through  minute  pores,  cinclides  (sing,  cinclis) ,  in  the 
body  wall. 

Make  a  drawing  of  the  contracted  animal. 

Internal  Anatomy. — Using  preserved  material,  place  the 
edge  of  a  razor  across  the  peristomial  area,  at  right  angles  to 
the  mouth-slit,  and  divide  the  animal  from  disk  to  base  into 
halves. 

1.  Note  the  extent  of  the  actinopharynx  and  siphono- 
glyphs;  they  lead  into  the  coelenteric  chamber.  Find  the 
extent  of  this  chamber,  and  the  method  of  its  subdivision  by 
delicate  partitions,  the  mesenteries,  or  septa.  Are  all  of  the 
mesenteries  alike? 

2.  Forming  the  free  edges  of  the  mesenteries,  below  the 
actinopharynx,  are  the  convoluted  mesenteric  filaments,  which 
are  secretory  organs  that  are  probably  equivalent  to  the 
gastric  filaments  of  the  Scyphozoa. 

3.  Quite  near  the  bases  of  the  mesenteries  are  the  attach- 
ments of  the  acontia.  What  relation  have  they  to  the  mesen- 
teric filaments?  Mount  living  acontia  under  a  cover  slip  in 
sea  water  and  notice  the  central  muscle  strand,  nematocysts, 
and  cilia. 

4.  Also  located  on  the  mesenteries,  and  arranged  parallel 
to  the  filaments,  but  back  from  the  edge  a  bit,  are  the  repro- 
ductive organs  or  gonads.  Are  they  found  on  all  of  the  mesen- 
teries? The  ova  or  spermatozoa  are  shed  into  the  coelenteric 
chamber  and  pass  out  through  the  mouth. 

Cut  one  of  the  halves  of  your  specimen  transversely  in  the 
region  of  the  actinopharynx,  and  study  the  arrangements  of 
the  mesenteries,  their  attachments,  etc. 


METRIDIUM  61 

5.  How  many  pairs  of  primary  mesenteries,  i.  e.,  those  at- 
tached both  to  the  outer  body  wall  and  to  the  actinopharynx, 
are  there?  The  directive  septa  are  those  at  the  angles  of 
the  actinopharynx.  The  portion  of  the  coelenteric  cavity 
between  any  two  pairs  of  mesenteries  is  termed  an  inter- 
radial  chamber.  The  space  between  the  two  mesenteries  of 
each  pair  is  called  an  intraradial  chamber. 

6.  Carefully  determine  the  disposition  of  the  longitudinal 
retractor  muscles  on  the  mesenteries.  Do  they  occupy  similar 
positions  on  all  of  the  mesenteries? 

7.  Examine  the  upper  parts  of  the  mesenteries  for  open- 
ings, septal  stomata,  that  put  the  chambers  in  communica- 
tion. 

8.  Are  the  tentacles  solid  or  hollow? 

Make  a  drawing  of  a  longitudinal  section  and  another  of 
a  cross  section.  Put  into  these  all  of  the  points  of  the  an- 
atomy you  have  seen. 

If  time  and  opportunity  permit,  it  is  very  desirable  that 
this  form  should  be  compared  with  specimens  of  the  order 
Madreporaria,  and  later  with  the  Alcyonaria.  Such  a  form 
as  Astrangia  may  easily  be  obtained  either  alive  or  properly 
preserved,  and  will  serve  to  show  the  relation  of  the  hard 
parts  of  the  coral  to  the  polyp.  You  should  understand  the 
relation  of  the  septa  and  the  mesenteries,  and  of  the  polyps 
to  each  other.  If  specimens  are  at  hand,  compare  such  forms 
as  Orbicella,  Favia,  and  Meandrina,  or  any  forms  that  show 
gradations  from  separate  calices  to  fused  groups,  and  under- 
stand the  positions  of  mouths,  the  arrangement  of  the  coelen- 
teric chambers,  and  the  way  in  which  the  colony  has  come 
to  its  present  form.  You  should  also  examine  large  branch- 
ing colonies  and  determine  why  branches  are  formed  and 
how  they  arise. 

Examine  the  structure  of  an  alcyonarian  colony  and  see 
how  the  polyps  are  placed.  The  structure  of  the  expanded 
polyps  is  nicely  shown  by  Renilla.  The  spicules  of  such 
forms  as  Gorgonia  may  be  obtained  by  boiling  a  portion  of 


62  COELENTERATA 

a  colony  in  caustic  potash.     What  purpose  do  such  spicules 
serve? 

Parker:    The  Reactions  of  Metridium  to  Food  and  Other  Substances. 

Bull.  Mus.  Comp.  Zool.,- Harvard,  29,  1896. 
:    The  Mesenteries  and  Siphonoglyphes  in  Metridium  marginatum. 

Bull.  Mus.  Comp.  Zool.,  Harvard,  30,  1897. 
:     Longitudinal    Fission   in   Metridium    marginatum.     Bull.    Mus. 

Comp.  Zool.,  Harvard,  35,  1899. 

The  Reversal  of  the  Effective  Stroke  of  the  Labial  Cilia  of  Sea- 


Anemones  by  Organic  Substances.     Am.  Jour.  Physiol.,  14,  1905. 

The  Origin  and  Significance  of  the  Primitive  Nervous  System. 


Bull.  Mus.  Comp.  Zool.,  Harvard,  50,  1911. 
— :    The  Elementary  Nervous  System.    Lippincott,  1918. 


CTENOPHORA 

Single.  Pelagic.  Eight  rows  of  meridional  swimming 
plates.  No  nettle  cells,  but  with  adhesive  cells.  With  aboral 
sense  organ.  This  phylum  consists  of  one  class  which  com- 
prises the  following  orders: 

Order  1.  Cydippida. 

Nearly  circular.  Two  tentacles,  each  of  which 
may  be  retracted  into  a  sheath.  (Pleurobra- 
chia,  Mnemiopsis.) 

Order  2.  Lobata. 

Compressed  in  the  vertical  plane.  Two  large 
oral  lobes.     No  tentacle  sheaths.     (Deiopea.) 

Order  3.  Cestida. 

Ribbon-shaped.  Two  tentacles  with  sheaths, 
and  numerous  other  tentacles.     (Cestus.) 

Order  4.  Beroida. 

Laterally  compressed.  Without  tentacles. 
(Beroe.) 

PLEUROBRACHIAi 

This  form  belongs  to  the  group  of  animals  popularly 
called  "comb  jellies,"  and  occurs  along  the  coast  in  irregular 
abundance  during  the  summer  months.  Specimens  are  very 
luminescent  when  disturbed,  so,  when  they  are  abundant, 
the  display  caused  by  them  while  rowing  at  night  is  some- 
times brilliant.  They  may  frequently  be  seen  during  the 
daytime  and  can  often  be  satisfactorily  observed  in  the  shade 
of  a  wharf  when  the  water  is  calm. 

Unmutilated,  living  material  can  be  studied  to  best  ad- 
vantage, but  preserved  material  may  be  had  that  is  quite 
satisfactory  for  anatomic  study. 

1  Although  the  following  section  is  written  especially  for  Pleuro- 
brachia,  little  difficulty  will  be  found  in  applying  it  to  the  related 
genus  Mnemiopsis  which  is  usually  very  abundant  in  the  vicinity  of 
Woods  Hole  during  the  late  summer. 

63 


64  CTENOPHOKA 

1.  In  general  appearance  a  specimen  resembles  a  hy- 
drozoan  medusa,  with  its  aboral  surface  elongated  until,  as  a 
whole,  it  approaches  the  shape  of  a  fowl's  egg. 

2.  The  broader  or  oral  end  bears  two  small  lip-like  lobes, 
between  which  is  the  slit-like  mouth.  We  may  consider  the 
elongation  of  the  mouth  to  be  in  the  anteroposterior  plane. 
Bilateral  symmetry  is  thus  evident. 

3.  At  the  aboral  pole  is  the  "sensory  body" 

4.  Leading  away  from  this  and  extending  as  meridional 
lines  toward  the  oral  pole  are  eight  ctenophoral  rows  of 
swimming  plates.  Examine  the  plates  with  a  hand  lens  and 
determine  their  structure  and  function.  Determine  the  po- 
sitions of  the  rows  with  respect  to  the  anteroposterior  plane. 

5.  By  the  sides  of  the  stomodaeum  are  a  pair  of  yellow- 
ish or  orange  tentacles  that  may  be  retracted  wholly  into  the 
tentacle  sheath  or  extended  through  pores  near  the  aboral 
pole.  When  extended  the  tentacles  are  seen  to  be  branched. 
They  are  very  sensitive  and  contractile. 

Digestive  System. — With  a  pipette  inject  a  solution  of 
carmin  into  the  mouth  opening. 

1.  You  can  then  more  plainly  see  the  long  ribbon-like 
stomodaeum  which  extends  two  thirds  of  the  distance  to  the 
sensory  body,  where  it  joins  the  infundibulum. 

2.  From  the  stomodaeum  are  given  off  the  canals,  which 
in  a  successful  injection  will  be  seen  to  be  as  follows: 

(a)  The  axial  funnel  tube  extending  to  the  sensory  body. 

(b)  Two  par  agastric  canals,  one  on  each  side,  passing 
down  along  the  stomodaeum. 

(c)  Two  tentacular  canals,  one  on  each  side,  passing  to 
the  tentacular  structures. 

(d)  Two  perradial  canals,  one  on  each  side,  each  of  which 
bifurcates  to  form  the  interradial  canals  (four  in  all),  each 
of  which  again  bifurcates  to  form  the  adradial  canals  (eight 
in  all),  which  are  continued  orally  and  aborally  just  beneath 
the  swimming  plates  as  the  meridional  canals.  These  canals 
end  blindly  without  intercommunication. 


PLEUROBRACHIA  65 

Reproductive  System. — The  ctenophore  is  hermaphroditic 
and  ova  and  spermatozoa  are  proliferated  from  the  walls  of 
the  meridional  vessels. 

A  portion  of  a  ctenophoral  row  should  be  cut  off,  and  ex- 
amined under  a  microscope,  to  ascertain  the  arrangement  and 
relation  of  plates  and  cilia. 

Make  a  drawing  of  a  side  view. 

Make  a  diagram  that  will  show  the  appearance  of  a  mer- 
idional cross-section. 

Abbott:    The  Morphology  of  the  Coeloplana.    Zool.  Jahrb.,  24,  1907. 

Agassiz,  A.:  Embryology  of  the  Ctenophorse.  Am.  Acad.  Arts  and 
Sci.,  10,  1874. 

Mayer:  Ctenophores  of  the  Atlantic  Coast  of  North  America.  Car- 
negie Inst,  of  Washington,  1912. 

Parker:  The  Movements  of  the  Swimming-plates  in  Ctenophores,  with 
Reference  to  the  Theories  of  Ciliary  Metachronism.  Jour.  Exp.  Zool., 
2,  1905. 

5 


PLATYHELMINTHES 

Body  elongated,  flattened  and  unsegmented.    Anus  gener- 
ally absent. 

Class  1.  Turbellaria. 

Outer  surface  ciliated.    Free  living. 

Order  1.  Polycladida. 

Intestine  complexly  branched.  No  separate 
vitellaria.   (Planocera,  Leptoplana,  Stylochus.) 

Order  2.  Tricladida. 

Intestine  with  anterior  median,  and  two  poste- 
rior lateral  limbs.  Vitellaria  numerous. 
(Planaria,  Bdelloura,  Syncoelidium.) 

Order  3.  Rhabdocoelida. 

Simple,  saclike  intestine.     Body  usually  elon- 
gated.    (Polychoerus,  Microstomum.) 
Class  2.  Trematoda. 

Parasitic.  Generally  with  sucking  disks.  Well- 
developed  digestive  system. 

Order  1.  Monogenetica. 

Ectoparasitic.  Direct  development.  Three  or 
more  suckers.     (Polystomum.) 

Order  2.  Digenetica. 

Endoparasitic.  Complicated  development. 
Never  more  than  two  suckers.     (Distomum.) 

Class  3.  Cestoda. 

Endoparasitic.  Without  digestive  cavity.  Usu- 
ally having  a  scolex,  bearing  clinging  organs 
(suckers  or  hooks). 

Order  1.  Monozoa. 

Body  not  divided  into  proglottids.  (Caryophyl- 
laeus.) 

Order  2.  Polyzoa. 

Body  consisting  of  scolex  and  proglottids. 
(Taenia,  Crossobothrium.) 

Class  4.  Nemertinea. 

Elongated,  ciliated,  with  eversible  proboscis 
not  directly  connected  with  the  alimentary 
canal.  Intestine  usually  with  lateral  divertic- 
ula. Anus  present.  (Tetrastemma,  Cere- 
bratulus.) 

66 


PLANARIA  67 

TURBELLARIA 

PLANARIA  MACULATA 

This  form  is  very  common  in  fresh-water  ponds  through- 
out the  United  States.  It  is  found  during  the  day  on  the 
lower  or  shaded  surfaces  of  stones  and  other  submerged  ob- 
jects, a  fact  which  suggests  that  it  is  nocturnal  in  its  habits. 
Most  fresh-water  planarians  have  very  opaque  bodies  and 
their  internal  organization  cannot  be  studied  in  the  fresh 
specimens. 

1.  Notice  the  general  shape  of  the  body. 

2.  The  methods  of  locomotion.     Look  for  cilia. 

3.  The  pharynx  and  mouth  near  the  middle  of  the  ven- 
tral surface. 

4.  The  eye  spots  on  the  anterior  dorsal  surface. 

5.  Try  feeding  specimens  by  crushing  a  live  pond-snail 
and  putting  the  fragments  in  the  dish  with  them.  If  any  of 
the  worms  are  at  rest,  set  them  in  motion  by  lifting  one  end 
of  each  with  a  bit  of  wood,  a  camel's-hair  brush,  or  some 
blunt  instrument.  Observe  the  animals  at  intervals  of  a  few 
minutes  and  see  if  any  of  them  begin  to  feed.  If  so,  by  turn- 
in  them  over  quickly  with  a  camel's-hair  brush,  try  to  see 
how  the  pharynx  is  used.  If  not  successful,  try  turning  a 
specimen  ventral  side  up,  and  placing  a  small  bit  of  snail 
meat  on  its  body  in  the  region  of  the  pharynx. 

6.  Look  among  the  specimens  in  the  dishes  on  the  prep- 
aration table  for  animals  that  show  marks  of  normal  fission. 

7.  Clean  a  heavy  watchglass  thoroughly  and  pour  it  about 
two  thirds  full  of  clean  pond  water  from  the  jar  on  the 
preparation  table.  Transfer  all  of  ^the  specimens  to  this  dish, 
lifting  each  carefully  with  a  camel's  hair  brush.  With  a 
scalpel  mutilate  them  in  various  ways;  cut  one  transversely, 
another  longitudinally,  another  into  several  pieces  of  various 
shapes.  Make  memoranda,  if  necessary,  of  the  shapes  of  the 
various  pieces.  Carefully  cover  the  dish  and  set  it  away. 
Examine  the  pieces  with  a  hand  lens  every  twenty-four  hours 


68  PLATYHELMINTHES 

for  the  next  week  or  ten  days.    Change  the  water  in  the  dish 
at  least  twice  a  week.    Do  not  use  water  from  the  tap. 

Curtis:  The  Life  History,  the  Normal  Fission,  and  the  Reproductive 
Organs  of  Planaria  maculata.     Proc.  Bost.  Soc.  Nat.  Hist.,  30,  1902. 

Morgan:  Experimental  Studies  of  the  Regeneration  of  Planaria  macu- 
lata.   Arch.  f.  Entwickelungsmech.,  7,  1898. 

Parker  and  Burnett:  The  Reactions  of  Planarians  With  and  Without 
Eyes  to  Light.    Am.  Jour.  Physiol.,  4,  1900. 

BDELLOURA  OR  SYNCOELIDIUM 

Most  triclads  are  free-living,  but  a  few  live  on  the  ex- 
ternal surfaces  of  other  animals.  The  above-mentioned  forms 
are  found  upon  the  proximal  joints  of  the  walking  legs  and 
in  the  gill  books  of  Limulus.  Owing  to  the  absence  of  pig- 
ment, they  are  very  favorable  for  the  study  of  internal  struc- 
ture, and  may  be  used  to  demonstrate  the  structures  not  ob- 
served in  Planaria  maculata. 

1.  Observe  the  movements  of  the  living  worms  in  a 
watchglass  of  sea  water;  then  place  a  specimen  on  a  slide, 
dorsal  side  uppermost,  and  cover  with  a  slip. 

If  any  of  the  points  of  structure  mentioned  for  Planaria 
have  not  been  observed,  try  to  find  them  on  this  form. 

2.  Notice  that  the  gut  with  its  three  main  branches  (tri- 
clad  type)  and  many  secondary  diverticula  is  easily  recog- 
nizable. The  mouth  can  sometimes  be  made  out  as  a  small 
circular  opening  leading  ventrally  from  the  posterior  end  of 
the  pharyngeal  sheath. 

Compress  the  specimen  as  much  as  possible  by  drawing 
off  the  water  with  filter  paper  and  look  for: 

3.  The  cerebral  ganglia,  a  bilobed  structure  beneath  the 
eye  spots,  that  appears  as  a  slightly  lighter  area. 

4.  From  the  cerebral  ganglia  two  longitudinal  nerve  cords 
pass  backward,  and  several  smaller  nerves  pass  off  in  front. 
Examine  the  specimen  by  reflected  light,  looking  particularly 
at  the  nervous  system  and  pharynx.  What  relation  have  the 
nerve  cords  behind? 

5.  With  the  high  power  and  good  light,  look  for  the  water- 


BDELLOURA   OR   SYNCOELIDIUM  69 

vascular  tubules.  These  tubules  are  more  easily  seen  in 
specimens  that  have  been  under  the  coverslip  some  time. 
The  region  anterior  to  the  cerebral  ganglia  is  a  favorable 
place.  They  form  a  clear,  branching  tracery,  a  little  lighter 
than  the  surrounding  tissue.  The  flicker  of  the  flame  cells 
can  usually  be  seen,  but  they  may  be  more  easily  seen  in 
Crossobothrium.  Examine  chart  and  textbook  figures  of  the 
water- vascular  system. 

Make  a  good-sized  drawing  of  a  worm,  showing  the  above 
points. 

Reproductive  Organs. — Turbellarian  worms  are  hermaph- 
roditic. In  this  form  the  various  organs  are  so  crowded  to- 
gether that  it  will  be  best  to  follow  each  system  separately. 
Compress  a  specimen  under  the  slip  and  find  the  male  or- 
gans as  follows: 

(a)  The  testes  are  the  numerous  rounded  masses  between 
the  lateral  branches  of  the  gut.  They  are  connected  by  means 
of  fine  tubes  which  cannot  be  seen  in  fresh  specimens. 

(6)  The  vasa  defer entia,  two  large  tubes,  one  on  either 
side  of  the  pharynx,  which  unite  posteriorly  near  the  base  of 
the  penis. 

(c)  The  genital  atrium,  within  which  the  penis  lies  with- 
drawn, is  situated  behind  the  pharynx.  The  penis  and  atrium 
may  be  considered  as  a  replica,  in  miniature,  of  the  pharynx 
and  its  sheath. 

If  the  above  structures  cannot  be  satisfactorily  seen,  try 
preserved,  stained,  and  mounted  specimens.1 

Draw  the  male  reproductive  system.  Refer  to  charts  and 
textbooks  for  anything  that  is  obscure. 

1  Specimens  may  be  readily  killed  by  compressing  under  a  slip, 
being  careful  to  draw  the  excess  of  fluid  out  on  one  side  so  that  the 
animal  cannot  contract,  and  running  in  killing  fluid.  (Sublimate  acetic 
is  good.)  As  soon  as  they  become  opaque  white,  put  on  enough  killing 
fluid  to  float  the  slip  off  and  transfer  the  specimens  to  a  dish  of  the 
fixative  for  five  minutes,  then  50  per  cent  alcohol  a  few  minutes,  70 
per  cent  several  hours,  stain  with  borax  carmine  or  Delafield's  hemat- 
oxylin; dehydrate,  clear  and  mount  in  balsam.  (See  directions  in  the 
appendix  for  making  permanent  preparations.) 


70  PLATYHELMINTHES 

The  female  organs  are  as  follows: 

(a)  Opening  into  the  genital  atrium  are  the  two  large 
sacs,  the  so-called  uteri,  which  lie  near  the  margins,  just  pos- 
terior to  the  end  of  the  pharynx.  Each  has  a  separate  open- 
ing on  the  ventral  surface  of  the  body,  but  has  no  direct 
connection  with  any  other  part  of  the  reproductive  system. 
These  may  not  be  homologous  with  the  single  uterus  found 
in  most  triclads.     (See  Wheeler.) 

{b)  Place  a  worm  ventral  side  up  and  look  carefully  be- 
tween the  second  and  third  or  the  third  and  fourth  anterior 
gut  diverticula  on  either  side  of  the  main  anterior  ramus  for 
the  two  ovaries. 

(c)  The  oviducts  pass  backward  from  the  ovaries,  parallel 
to  the  vasa  deferentia,  and  unite  posterior  to  the  penis.  The 
common  duct  thus  formed  enters  the  posterior  part  of  the 
genital  atrium.  The  oviduct  is  difficult  to  demonstrate  and 
it  may  be  necessary  to  try  both  fresh  and  stained  material. 

{d)  Along  the  margins  of  the  animal,  between  the,  diver- 
ticula of  the  gut,  are  rounded  bodies,  the  vitellaria.  These 
discharge  their  products  into  the  oviducts.  What  is  their 
function? 

Draw  the  female  reproductive  system. 

Study  stained  and  mounted  specimens  for  any  points 
which  have  not  been  found,  and  particularly  examine  the 
nervous  system.  Look  for  the  marginal  nerve  running  along 
the  edge  of  the  body,  and  for  numerous  transverse  commis- 
sural nerves.  How  many  of  these  are  there?  How  regular 
is  their  arrangement?1 

Wheeler:     Syncoelidium    pellucidum,    a    new    Marine    Triclad.      Jour. 
Morph,.  9,  1894. 

TREMATODA 

Trematodes  are  flat  worms  which  lead  a  wholly  parasitic 
life,  but  which  have  retained,  to  a  greater  or  less  degree,  those 

XA  Polyclad,  Planocera,  can  often  be  obtained  from  the  mantle 
chamber  of  Busycon.  If  Busycon  is  allowed  to  remain  out  of  water  for 
some  hours  the  Planocera  usually  crawl  out.  The  form  is  fairly  satis- 
factory for  study. 


PNEUMONECES  71 

organs  that  characterize  free-living  animals.  Some  Trem- 
atodes  are  parasitic  upon  the  outside  (or  ectoderm)  of  other 
animals,  and  are  hence  called  ectoparasites. 

PNEUMONECES 

This  form  is  found  as  a  parasite  in  the  lungs  of  frogs. 
In  some  localities  a  large  proportion  of  the  frogs  are  infested 
and  several  specimens  are  frequently  found  in  one  frog.  The 
host  of  the  asexual  generation  of  this  species  is  not  known, 
but  in  a  closely  allied  species  the  asexual  generation  lives  in 
the  pond  snail.  The  living  worm  is  cylindrical  and  pointed 
at  both  anterior  and  posterior  ends.  With  a  low-power  ob- 
jective note: 

1.  The  anterior  sucker,  surrounding  the  mouth. 

2.  The  ventral  sucker,  near  the  middle. 

3.  Whether  eyes  are  present  or  not. 

4.  The  alimentary  canal, 
(a)  The  mouth. 

{b)  The  muscular  pharynx. 

(c)  The  intestine  which,  soon  after  leaving  the  pharynx, 
divides  into  two  equal  branches,  passing  one  on  the  left  and 
one  on  the  right  side,  to  near  the  end  of  the  body.  These 
intestinal  branches  do  not  send  out  lateral  branches  as  they 
do  in  Bdelloura. 

The  Water-vascular  System. — A  small  opening  will  be 
found  at  the  posterior  end  of  the  body  from  which  a  duct 
passes  forward  in  a  median  position  to  a  point  a  little  pos- 
terior to  the  median  sucker.  Here  it  divides  and  sends  a 
branch  on  either  side  of  the  worm  to  near  the  anterior  end. 

The  Nervous  System. — This  is  difficult  to  see,  but  in  a 
mounted  specimen  a  small,  deeply  stained  mass,  the  cerebral 
ganglia,  may  be  visible  on  either  side  of  the  pharynx.  Three 
pairs  of  longitudinal  nerves  pass  back  to  near  the  posterior 
end  of  the  body. 

Make  a  drawing  showing  the  above  structures  indicating 
all  you  have  been  able  to  observe. 


72  PLATYHELMINTHES 

The  Reproductive  Organs. — Male:  Two  large  bodies,  the 
testes,  very  definite  in  outline,  occupy  the  posterior  end  of 
the  animal.  A  duct  from  each,  the  vas  deferens,  passes  for- 
ward, and  the  two  unite  just  posterior  to  the  point  where  the 
intestine  branches.  By  means  of  a  median,  common  duct, 
they  open  to  the  exterior  through  the  male  genital  opening. 
This  is  situated  on  the  ventral  surface,  just  below  the  point 
where  the  intestine  branches. 

Female:  Some  of  the  ducts  are  difficult  to  see,  and  in 
many  cases  they  cannot  be  followed,  but  some  of  the  organs 
can  be  found  in  most  of  the  specimens. 

The  ovary  is  a  lobed  organ  lying  a  little  to  one  side  of 
the  middle  of  the  animal,  and  just  anterior  to  the  testes. 
Lying  against  it  is  the  saclike  ootype,  into  which  the  ovary 
opens.  From  the  posterior  end  of  the  ootype  the  long,  coiled, 
ductlike  uterus  passes  backward  to  near  the  posterior  end 
of  the  animal,  turns  and  passes  forward,  and  finally  opens  at 
a  point  on  the  ventral  surface  near  the  male  opening.  The 
uterus  of  an  adult  usually  contains  embryos  and  fills  the 
body,  so  as  to  obscure  the  other  parts. 

The  vitellaria  consist  of  numerous  small,  rounded  masses, 
that  lie  near  the  margins  of  the  animal.  The  products  of 
these  organs  are  emptied  into  the  ootype  through  a  short 
common  duct,  just  ventral  to  the  ootype.  Do  you  know  what 
they  are  for?  Laurer's  canal  is  a  short  duct  which  leads 
from  the  ootype  to  the  exterior.     Its  function  is  doubtful. 

Cort:    North  American  Frog  Lung  Flukes.    Trans.  Am.  Micr.  Soc,  34, 

1915. 
Goto:    Studies  on  the  Ectoparasitic  Trematodes  of  Japan.     Jour.  Col. 

Sci.  Imp.  Univ.  Tokyo,  8,  1894. 
Linton:    The  Process  of  Egg  Making  in  the  Trematode.     Biol.  Bull., 

14,  1908. 
Leuckart:    Die  Blasenwurmer  und  ihre  Entwicklung.     1856. 

:    Die  Parasiten  des  Menschen. 

Schauinsland :     Beitrag    zur    Kenntnis    der    Embryonalentwicklung    der 

Trematoden.    Jen.  Zeit.  f.  Naturwiss.  Neue  Folge,  9,  1883. 
Thomas:    Development  of  the  Liver  Fluke.     Quart.  Jour.  Mic.  Sci.,  23, 

1883. 


PNEUMONECES,    CRYPTOCOTYLE  73 

CRYPTOCOTYLE 

One  of  the  most  favorable  digenetic  trematodes  for  study 
of  the  life  history  is  Cryptocotyle  lingua.  Adults  of  this 
species  are  found  in  the  intestine  of  fish-eating  birds  and 
mammals.  Larval  stages  may  be  found  in  the  common 
marine  snail,  Littorina  litorea. 

Observe  the  living  and  preserved  adult  Cryptocotyle  and 
make  a  drawing  to  show  the  difference  in  morphology  be- 
tween this  species  and  Pneumoneces. 

The  Rediae. — Remove  Littorina  litorea  from  its  shell.  If 
the  liver  is  grayish,  shrunken  and  irregular  in  appearance  it 
will  be  found  to  contain  numerous  rediae  and  cercariae. 
Transfer  to  a  slide  and  study.    Note  the  following: 

(a)  Rediae  with  characteristic  mouth  and  pharynx. 

(b)  The  numerous  cercariae  in  various  stages  of  develop- 
ment. 

The  Cercaria. — Obtain,  from  the  assistant,  material  con- 
taining mature  cercariae  of  Cryptocotyle  which  have  emerged 
from  an  infected  Littorina  kept  over-night  in  a  finger  bowl. 
To  this  add  a  drop  of  1 :  1000  neutral  red  solution  and  cover. 
As  the  cercariae  become  quiet  look  for  the  following:  mouth, 
pharynx,  "penetration  glands,"  tail  fin,  flame  cells,  excretory 
vesicle,  and  germinal  cells. 

Encystment  of  cercariae. — To  a  watch  glass  filled  with 
sea  water,  add  first  a  piece  of  cunner  fin  and  then  several 
mature  cercariae. 

Observe  and  describe  the  activities  of  the  cercariae  dur- 
ing encystment. 

Metacercariae. — Study  and  draw  metacercariae  of  Cryp- 
tocotyle as  they  appear  when  encysted  in  a  cunner  fin. 

Stunkard:  The  Life  History  of  Cryptocotyle  lingua  (Creplin),  with 
Notes  on  the  Physiology  of  the  Metacercariae.  Jour.  Morph.  and 
Physiol.,  50,  1930. 

CESTODA 

The  Cestoda,  or  tapeworms,  are  endoparasites  which  pos- 
sess very  few  of  those  organs  that  are  characteristic  of  free- 


74  PLATYHELMINTHES 

living  animals.  They  have  no  alimentary  canal,  probably 
no  organs  of  special  sense,  and,  except  in  the  head,  the  ner- 
vous system  is  feebly  developed.  On  the  other  hand,  the 
organs  needed  for  the  reproduction  of  the  species  are  enor- 
mously developed,  so  that  in  the  more  mature  portions  of 
the  animal,  the  ovaries,  testes,  and  accessory  organs  occupy 
nearly  the  whole  space.    Can  you  explain  this  condition? 

CROSSOBOTHRTUM  LACINIATUM 

This  tapeworm  passes  its  adult  life  in  the  intestine  (spiral 
valve)  of  the  sand  shark.  Cestode  larvae  which  may  be  the 
young  of  this  species  are  abundant  in  the  cystic  duct  of  the 
squeteague.  How  the  developing  eggs  and  embryos  are  con- 
veyed from  the  shark  to  the  squeteague  is  not  known.  The 
transfer  of  the  larvae  from  the  squeteague  to  the  alimentary 
canal  of  the  shark  can  be  easily  understood. 

Adult  Stage. — 1.  Notice  specimens  that  are  attached  to 
the  wall  of  the  intestine  of  the  shark. 

2.  Observe  movements  of  specimens  in  a  dish  of  sea  water. 
Do  the  suckers  have  independent  movements? 

3.  With  a  low  power  of  the  compound  microscope,  or  with 
a  hand  lens,  note  that  the  worm  is  made  up  of  a  head  por- 
tion, the  scolex,  and  of  numerous  "segments,"  the  proglottids. 
What  is  the  relative  size  of  the  proglottids  in  the  different 
regions  of  any  specimen?  Where  are  new  proglottids  pro- 
duced? (See  Curtis.)  Are  the  proglottids  attached  to  one 
another  with  equal  firmness  in  all  parts  of  the  body?  Note 
their  peculiar  shape,  and  how  they  are  connected  together. 
In  the  above  examination,  if  living  material  is  used  it  will 
often  be  desirable  to  stretch  portions  of  the  animal  very 
gently  with  your  forceps. 

4.  Note  the  number  and  arrangement  of  the  disk-like 
suckers.  How  are  they  borne  on  the  scolex?  Do  you  find 
each  sucker  to  be  entirely  simple? 

Draw  the  adult  worm. 

5.  Cut  from  the  head  end  of  a  living  specimen  a  piece 


CROSSOBOTHRIUM  75 

consisting  of  a  scolex  and  not  more  than  one  or  two  proglot- 
tids.  Place  this  on  a  slide,  cover,  being  careful  not  to  com- 
press too  much  at  first,  and  examine  the  scolex  carefully 
again  to  make  sure  you  understand  its  structure. 

6.  Look  for  transparent  tubes  coiling  about  in  the  scolex 
and  its  suckers.  Compress  the  specimen  by  drawing  off  as 
much  water  as  possible  with  filter  paper,  and  look  again  for 
the  transparent  tubes.  These  are  portions  of  the  water  vas- 
cular system.  Recall  the  description  of  this  system  given  in 
the  lecture  or  in  textbooks.  The  finer  branches  which  lead 
from  the  main  trunks  are  difficult  to  identify  with  certainty, 
but  by  using  the  high  power  of  your  microscope,  and  focusing 
just  below  the  surface  in  the  more  transparent  portions  of 
the  scolex,  the  flame  cells  may  easily  be  seen.  The  "flame" 
appears  like  a  short,  thick  whip  lost  in  continual  vibration. 
Find  such  flames  and  watch  them  carefully.  If  not  found  at 
once,  let  the  preparation  stand  and  examine  in  about  half  an 
hour.  In  the  older  preparation  they  are  frequently  easier 
to  find. 

7.  In  both  scolex  and  proglottids  of  fresh  specimens  many 
clear,  transparent,  threadlike  muscle  fibers  may  be  seen. 
There  will  also  be  found  an  abundance  of  clear,  rounded 
granules  of  lime. 

8.  Watch  the  movements  of  the  large,  detached  proglottids. 
Pull  proglottids  from  the  posterior  end  of  the  specimen  to  see 
how  easily  they  may  be  detached.  Very  many  tapeworms 
have  these  "motile  proglottids,"  which  in  some  cases  remain 
alive  for  so  long  after  being  detached  as  to  seem  almost  like 
independent  animals.  Ripe  proglottids,  taken  from  the  in- 
testinal fluid  of  the  host  and  placed  in  sea  water,  begin  within 
a  few  minutes  to  extrude  eggs.  Extrusion  is  accompanied  by 
peculiar  and  extensive  muscular  contractions. 

Mount  stained  specimens  of  proglottids  in  balsam  and 
study  the  reproductive  organs.1 

1  Specimens  may  be  killed  in  the  manner  described  for  Bdelloura. 
Enough  pressure  should  be  used  to  flatten  the  proglottids  decidedly. 


76  PLATYHELMINTHES 

1.  On  one  side  of  the  proglottid  the  lateral  genital  aperture 
will  be  seen.  The  penis  is  a  long,  slender  organ,  found  pro- 
truding, or  lying  in  its  sheath  near  the  lateral  aperture.  The 
vas  deferens,  a  long,  convoluted  tube,  extends  from  the  penis 
to  the  testes,  which  form  many  rounded,  deeply  stained  struc- 
tures that  lie  about  the  oval  outline  of  the  uterus.  On  leaving 
the  penis  the  vas  deferens  extends  toward  the  pointed  end  of 
the  proglottid,  along  the  side  of  the  uterus,  until  it  reaches  a 
point  anterior  to  it,  where  it  may  sometimes  be  seen  sending 
branches  to  the  testes,  but  is  frequently  lost.  Throughout  its 
length  it  is  greatly  convoluted  and  is  generally  filled  with 
spermatozoa. 

2.  At  the  base  of  the  penis,  in  the  lateral  genital  aperture, 
is  the  external  opening  of  the  female  organs.  From  this  point 
a  small  tube,  the  vagina,  leads  to  a  point  below  the  saclike 
uterus,  which  is  sometimes  very  large  and  sometimes  col- 
lapsed and  small.  The  vagina  ends  in  a  small  pouch,  the 
ootype,  from  which  a  short  canal  (sometimes  visible,  but 
more  often  obscured  by  the  vagina,  which  lies  above  or  below 
it)  leads  to  the  uterus. 

3.  The  ovary  consists  of  a  large  many-fingered  mass  in  a 
median  position,  near  the  posterior  end  of  the  proglottid.  It 
surrounds,  more  or  less  completely,  the  inner  end  of  the 
vagina  and  ootype. 

4.  The  vitellaria  occupy  the  posterior  corners  of  the  pro- 
glottid, and  may  extend  anteriorly  along  its  margins,  by  the 
sides  of  the  testes,  nearly  to  its  anterior  extremity.  The 
ducts  from  the  vitellaria  unite  and  join  the  ootype. 

5.  The  shell  gland  is  a  small  median  mass  that  is  situated 
between  the  lobes  of  the  ovary  around  the  ootype. 

Understand  the  relation  of  the  ducts  of  the  shell  glands, 
vitellaria,  and  vagina  to  the  ootype  and  uterus,  how  and 
where  the  eggs  are  fertilized,  and  how  they  are  finally  lodged 
in  the  uterus.  Why  should  hermaphroditism  occur  in  this 
form? 

Draw  a  figure  of  the  proglottid  showing  all  of  the  parts 
you  have  seen. 


CROSSOBOTHRIUM,    TETRASTEMMA  77 

Larval  Stage. — Examine  and  draw  a  specimen  of  the  larva 
found  in  the  cystic  duct  of  the  squeteague.  The  scolex  with 
its  suckers  at  the  anterior  end,  and  the  opening  of  the  water- 
vascular  system  at  the  posterior  end,  are  readily  seen.  Com- 
press slightly  if  the  trunks  of  the  water  vascular  system  are 
not  easily  seen.  They  can  always  be  seen  in  preserved  and 
stained  specimens  that  have  been  killed  under  pressure.  If 
you  have  trouble  in  seeing  them,  examine  such  a  specimen. 
Do  you  find  proglottids?  Understand  the  relation  of  this 
larva  to  a  true  cysticercoid. 

Curtis:    Crossobothrium  laciniatum  and  Developmental  Stimuli  in  the 

Cestoda.     Biol.  Bull.,  5,  1903. 
:     The   Formation    of   Proglottids   in   Crossobothrium    laciniatum. 

Biol.  Bull.,  11,  1906. 
Linton:    A  Cestode  Parasite  in  the  Flesh  of  the  Butterfish.     Bull.  U. 

S.  Bur.  Fish.,  26,  1906. 
Tennent:    A  Study  of  the  Life-history  of  Bucephalus  haimeanus:    A 

Parasite  of  the  Oyster.    Quart.  Jour.  Mic.  Sci.,  49,  1906. 

NEMERTINEA1 

Several  representatives  of  this  group  are  rather  easily  ob- 
tained. Some  of  these,  as  some  species  of  Cerebratulus  and 
Meckelia,  are  large,  but  they  are  generally  unsatisfactory  for 
anatomic  study,  as  they  are  opaque  and  filled  with  a  con- 
nective-tissue parenchyma  that  binds  the  organs  together. 
Furthermore,  they  are  especially  likely  to  cut  themselves  into 
small  pieces  by  contraction  of  muscles  in  the  body  wall. 

TETRASTEMMA 

This  small  animal  lives  among  the  forms  that  are  gener- 
ally found  attached  to  piles.  Specimens  can  usually  be  found 
by  placing  scrapings  from  piles  in  a  glass  jar  with  a  little  sea 
water  and  allowing  them  to  stand  from  a  half  hour  to  three 
hours.  The  animals  may  then  be  found,  with  the  aid  of  a 
lens,  on  the  sides  of  the  dish,  usually  near  the  surface. 

With  a  pipette  transfer  a  specimen  to  a  slide,  cover  it, 

xThis  group  is,  by  many,  considered  as  a  separate  phylum. 


78  PLATYHELMINTHES 

and  examine  with  low  and  high  powers  of  the  microscope. 
Notice : 

1.  The  shape  of  the  body,  the  four  eye  spots,  and  the  sen- 
sory ciliated  grooves. 

2.  The  straight  alimentary  canal.  The  diverticula  of  the 
intestine  and  the  terminal  anus. 

3.  The  enormous  proboscis,  consisting  of  a  large  anterior 
eversible  portion,  and  a  smaller  posterior  portion  that  is  not 
eversible.  Stylets  are  present  in  the  eversible  portion,  near 
its  inner  end.  Can  you  determine  how  the  proboscis  is  pro- 
truded and  retracted?  Does  the  proboscis  have  any  connec- 
tion with  the  digestive  system? 

4.  Beneath  the  posterior  eye  spots  are  the  cerebral  ganglia, 
from  which  lateral  nerve  cords  extend  posteriorly. 

5.  If  the  specimen  happens  to  contain  eggs,  they  will  lie 
between  the  diverticula  of  the  intestine.  They  are  compara- 
tively large. 

Coe:    Development  of  the   Pilidium   of   Certain  Nemerteans.     Trans. 

Conn.  Acad.,  10,  1899. 
:    On  the  Anatomy  of  a  Species  of  Nemertean  (Cerebratulus  lac- 

teus).    Trans.  Conn.  Acad.,  10,  1899. 

Series  of  papers  on   Regeneration   in  Nemertinea.     Jour.  Exp. 


Zool.,  54,  57,  61,  67  (1929-34) ;  Biol.  Bull.,  66,  1934. 

Verrill:     The    Marine    Nemerteans    of    New    England    and    Adjacent 

Waters.     Trans.  Conn.  Acad.  Sci.,  8,  1892. 
Wilson,  C.  B.:    Habits  and  Early  Development  of  Cerebratulus  lacteus. 

Quart.  Jour.  Mic.  Sci.,  43,  1900. 


NEMATHELMINTHES 

Body  elongated,  cylindrical,  and  not  segmented.  They 
have  a  very  general  distribution  and  a  great  diversity  of 
forms.  Many  are  parasitic.  Anus  usually  present.  Coelom 
not  filled  with  parenchyma.  The  classes  may  not  be  geneti- 
cally related. 

Class  1.  Nematoda. 

Many  are  internal  parasites,  but  others  are  found 
in  fresh  and  salt  water  and  in  damp  earth.  Body 
pointed  at  both  ends.  Mouth  terminal,  anus  ven- 
tral.    (Ascaris,  Trichinella,  Gordius.) 

Class  2.  Acanthocephala. 

Formidable  intestinal  parasites.  Proboscis  bear- 
ing hooks.  No  alimentary  canal.  Macracantho- 
rhynchus   (Echinorhynchus) . 

Class  3.  Chaetognatha.  . 

Marine,  and  all  but  one  species  pelagic.  With 
caudal  and  lateral  fins  and  bristle-like  jaws. 
(Sagitta.) 

ASCARIS 

Animals  belonging  to  this  genus  are  common  in  the  intes- 
tine of  the  horse  and  pig,  and  are  not  uncommon  in  man. 
Examine  specimens  and  see  if  they  have  any  organs  that 
would  aid  them  in  clinging  to  the  intestinal  wall.  How  can 
they  retain  their  positions? 

1.  Can  you  determine  which  is  anterior  and  which  is  pos- 
terior? Is  there  any  indication  of  segmentation?  Can  the 
ventral  side  be  distinguished  from  the  dorsal? 

2.  Find  the  mouth  and  see  that  it  is  bounded  by  three  lips. 
Notice  how  these  are  placed  and  find  the  papillae  on  the 
ventral  ones.  Find  the  anus  and  note  its  position.  This 
serves  also  as  a  reproductive  aperture  for  the  male.  In  the 
female  the  reproductive  aperture  is  situated  about  one  third 

79 


80  NEMATHELMINTHES 

back  from  the  anterior  end.    It  can  be  seen  only  in  favorable 

specimens. 

3.  Open  a  well  preserved  or  fresh  specimen  along  the  dor- 
sal line  and  notice  the  definite  cavity,  and  the  straight  ali- 
mentary canal.  If  the  specimen  is  a  female,  find  the  Y- 
shaped  genital  organs,  the  free,  ovarian  ends  of  which  are 
slender  and  somewhat  tangled.  The  position  of  the  external 
genital  opening  has  already  been  noted.  In  the  male  there 
is  a  single,  tangled,  threadlike  testis,  which  joins  the  enlarged 
seminal  vesicle  that  extends  to  the  cloaca.  The  nervous  sys- 
tem consists  of  a  circumesophageal  ring,  six  longitudinal 
nerves,  the  dorsal  and  ventral  of  which  are  larger  than  the 
others,  and  anterior  nerves.    It  is  not  easily  seen. 

A  drawing  is  desirable. 

Montgomery:    The   Adult   Organization   of   Paragordius  varius.     Zool. 
Jahrb.,  18,  1903. 

TRICHINELLA 

Encysted  specimens  may  occasionally  be  found  by  exam- 
ining thin  pieces  of  pig  muscle  obtained  from  the  meat 
market.  Pigs  fattened  in  small  pens  and  fed  on  table  waste, 
or  in  slaughter  yards  and  fed  on  the  offal  of  butchered 
animals,  are  much  more  likely  to  be  infected  than  others. 
Scavenger  rats  and  cats  are  frequently  infected. 

1.  Flatten  a  piece  of  muscle  containing  trichinellae  between 
two  slides  in  a  little  glycerin  and  notice  the  relation  of  the 
animal  to  the  muscle  fibers.  Notice  the  cyst  that  surrounds 
it  and  see  if  you  can  determine  whether  this  was  formed  by 
the  host  or  the  parasite.  There  are  frequently  fat  cells  at  the 
ends  of  the  cyst.  Just  after  the  parasites  are  encysted,  the 
cysts  are  surrounded  by  capillaries  that  may  be  injected  by 
injecting  the  vessels  of  the  host  These  may  be  found  only  at 
a  definite  stage  after  encystment.  Why  are  they  formed? 
Do  they  indicate  how  the  cysts  were  formed?  If  the  trich- 
inellae are  abundant  see  if  you  can  find  more  than  one  in 
a  cyst. 


ASCARIS,    TRICHINELLA,    METONCHOLAIMUS  81 

2.  Notice  the  shape  that  is  assumed  by  the  parasite.  Is 
the  coiling  always  the  same?  If  your  material  is  fresh,  mount 
some  of  the  muscle  between  slides  without  glycerin,  warm  the 
slide,  and  see  if  the  encysted  animals  will  move. 

3.  Are  the  anterior  and  posterior  ends  alike?  Is  there  any 
indication  of  a  mouth?  The  large  cells  that  form  the  intes- 
tine can  frequently  be  seen.  It  should  be  borne  in  mind  that 
the  encysted  specimen  is  not  fully  adult  and  that  the  animal 
grows  after  reaching  the  alimentary  canal  of  the  next  host. 

Make  a  drawing  of  an  encysted  animal. 

Glazier:    Report  on  Trichinae  and  Trichinosis.    U.  S.  Treas.  Dept.  Doc. 
No.  84,  Marine  Hospital,  1881. 

METONCHOLAIMUSi 

This  species,  Metoncholaimus  pristiurus,  is  a  free-living 
nematode  found  in  the  mud  in  shallow  salt  water.  It  belongs 
to  a  large  marine  group,  the  Oncholaiminae  (type  genus, 
Oncholaimus,  "tooth  in  the  throat"). 

1.  Make  a  preliminary  examination  of  several  specimens 
in  a  Syracuse  dish  using  a  binocular  dissecting  microscope. 
Observe  the  characteristic  coiling  and  uncoiling  movements. 
Distinguish  the  blunt  anterior  end  from  the  more  pointed  pos- 
terior end.  In  some  specimens  large  beadlike  structures  may 
be  seen  near  the  middle  of  the  body.  These  are  eggs  and 
serve  to  identify  the  females. 

Select  a  female  and  place  in  a  drop  of  fresh  water  for  one 
to  two  minutes  until  it  is  quiet  and  then  mount  immediately 
in  clear  sea  water.  Flatten  the  animal  slightly  by  removing 
water  from  under  the  cover  glass. 

2.  The  Digestive  System. — Note  that  the  posterior  end 
tapers  rapidly  and  is  slightly  curved.  The  anterior  end 
tapers  gradually.  Along  the  sides  of  both  are  numerous  sen- 
sory setae.  The  mouth  is  at  the  truncated  extremity  of  the 
anterior  end.     Behind  the  mouth  is  the  short  pharynx  with 

aThe  laboratory  directions  given  above  have  been  adapted  from 
directions  originally  furnished  by  the  late  Dr.  N.  A.  Cobb. 

6 


82  NEMATHELMINTHES 

sharply  pointed  teeth.  The  esophagus  running  posteriorly 
from  the  pharynx  is  a  thick-walled  tube.  A  sphincter  valve 
at  its  posterior  end  marks  the  beginning  of  the  intestine,  a 
yellowish-brown  tube  running  nearly  the  entire  length  of  the 
body.  Focussing  on  the  anterior  part  of  the  intestine  will 
show  that  its  wall  is  made  up  of  columnar  epithelium.  The 
inner  ends  of  most  of  the  epithelial  cells  are  filled  with  gran- 
ules giving  the  intestinal  wall  its  color.  The  anus  lies  about 
half  way  along  the  tapering  tail  and  the  rectum  runs  forward 
from  it  at  an  angle. 

3.  The  Nervous  System. — At  the  anterior  end  of  the  worm 
the  nerve  ring  may  be  seen  encircling  the  esophagus  about 
midway  of  its  length.  Running  backward  from  the  nerve  ring 
are  strands  of  nerve  fibers  which  connect  with  ganglion  cells 
between  the  esophagus  and  the  body  wall.  In  a  specimen 
previously  stained  with  methylene  blue  the  distribution  of 
the  ganglion  cells  with  relation  to  the  sensory  setae  may  be 
noted.  The  longitudinal  nerve  cords,  characteristic  of  many 
nematodes,  are  not  well  developed  in  Metoncholaimus. 

4.  The  Female  Reproductive  System. — A  short  distance 
anterior  to  the  large  thick-shelled  eggs,  lying  in  the  uterus, 
may  be  seen  a  row  of  cuboidal  cells,  each  approximately 
equal  to  the  diameter  of  the  body.  These  are  oocytes  and 
progressively  more  advanced  stages  may  be  seen  toward  the 
anterior  end,  where  mature  oocytes  as  large  as  the  eggs  may 
sometimes  be  observed.  At  the  posterior  end  of  the  ovary 
a  cluster  of  small  rounded  oogonia  may  be  seen  by  careful 
focussing.  The  funnel-like  opening  of  the  oviduct  may  be 
observed  at  the  anterior  end  of  the  ovary.  The  oviduct  itself 
is  difficult  to  find.  It  runs  backward  parallel  to  the  ovary 
and  opens  into  the  anterior  end  of  the  uterus.  A  varying 
distance  posterior  to  the  last  egg  in  the  uterus  may  be  seen 
a  low  papilla  with  an  opening,  the  vulva,  the  external  orifice 
of  the  female  genital  system. 

5.  The  Demanian  System. — This  system  is  found  only  in 
the  female.    Its  function  seems  to  be  accessory  to  the  female 


METONCHOLAIMUS  83 

reproductive  system.  It  consists  of  the  following  structures 
— the  moniliform  glands,  two  large,  clear,  cross-striated  tubes, 
lying  a  short  distance  anterior  to  the  rectum.  These  glands 
open  posteriorly  by  separate  pores.  Anteriorly  these  tubes 
unite  near  a  very  obvious  structure,  the  rosette.  From  the 
rosette  a  tube  runs  to  the  intestine,  and  another  tube,  start- 
ing as  a  wide  ampulla,  soon  narrows  rapidly  to  form  a  thin 
tube,  which  joins  the  uterus  in  the  vicinity  of  the  vulva. 

Make  a  large  drawing  of  a  female  Metoncholaimus  to 
show  as  many  of  the  above  features  as  you  have  been  able 
to  make  out.  If  possible  make  also  diagrammatic  cross  sec- 
tions of  the  body  (1)  in  the  region  of  the  esophagus  and  nerve 
ring  (2)  in  the  midovarian  region  and  (3)  through  the  monili- 
form glands. 

The  Male  Metoncholaimus. — In  the  manner  already  de- 
scribed mount  several  specimens  as  large  as  the  female  but 
showing  no  eggs.  These  are  probably  males.  Compare  the 
posterior  end  with  that  of  the  female.  Do  you  find  any  trace 
of  the  demanian  system?  The  opening  of  the  male  genital 
system  is  just  anterior  to  the  anus.  Two  slender  rodlike 
spicula  may  be  seen  running  forward  from  it  for  some  dis- 
tance. Anterior  to  the  spicula  is  the  ejaculatory  duct,  which 
is  connected  with  the  vas  deferens.  The  latter  is  usually 
difficult  to  see.  Careful  focussing  in  the  midregion  of  the 
body  will  enable  one  to  see  the  clear,  colorless  cells  which 
constitute  the  elongated  testes,  one  anterior  and  one  posterior. 
In  each  testis  there  is  a  progression  of  stages  from  before 
backward.  A  study  of  the  length  of  this  organ  will  show 
spermatogonia  and  all  stages  in  spermatocyte  growth.  Occa- 
sionally mitotic  figures  are  observable. 

Make  a  drawing  of  the  male  Metoncholaimus. 


TROCHELMINTHES 

Minute  animals  whose  adult  structure  seems  to  be  related 
to  that  of  the  trochophore  larva.  Mouth  usually  surrounded 
by  a  circlet  of  cilia.  Three  classes  (Rotifera,  Dinophilea,  and 
Gastrotricha)  are  referred  to  this  phylum,  but  they  may  not 
be  genetically  related. 

ROTIFERA 

Mostly  fresh-water  forms,  but  a  few  are  marine.  All  are 
of  microscopic  size.  The  pharynx  is  provided  with  a  mastica- 
tory apparatus,  and  the  anterior  end  bears  a  trochal  disk. 
Most  rotifers  are  free,  but  a  few  are  permanently  attached, 
and  some,  as  Melicerta,  live  in  tubes  of  their  own  formation. 

BRACfflONUS  (A  Rotifer) 

These  animals  are  frequently  quite  abundant  in  ponds  and 
aquaria.  They  are  not  very  active,  and  spend  most  of  their 
time  near  the  bottom  among  the  plants  and  debris.  Owing 
to  their  minute  size,  they  must  be  studied  with  a  high  power 
of  the  microscope. 

1.  The  body  is  divided  into  a  trunk,  which  is  inclosed  in  a 
transparent  cuticular  lorica,  and  a  movable  tail  or  foot.  The 
tail  is  tipped  with  two  processes  which  form  forceps,  by 
means  of  which  it  attaches  itself  to  plants.  Can  you  see  how 
these  are  used?    Why  does  the  animal  need  to  attach  itself? 

2.  Projecting  anteriorly  from  the  lorica  is  the  retractile 
trochal  disk.  Notice  the  cilia  on  the  margin  of  this  disk.  Is 
the  disk  used  in  locomotion?  Does  the  animal  always  move 
when  the  cilia  are  active?  What  other  use  has  the  disk?  Is 
the  animal  entirely  dependent  upon  the  cilia  of  the  disk  for 
locomotion? 

3.  The  mouth  is  at  the  ventral  border  of  the  trochal  disk 
and  leads  by  a  short  buccal  cavity  to  the  mastax,  which  is  a 

84 


BRACHIONUS  85 

muscular  apparatus  provided  with  three  chitinous  trophi  (a 
median  incus  and  two  mallei).  It  is  used  in  grinding  the 
food.  The  grinding  movements  are  easily  seen.  A  very  short 
gullet  leads  from  the  mastax  to  the  large  stomach.  The  in- 
testine is  short  and  thick  and  opens  into  a  cloaca.  The  anus 
is  near  the  base  of  the  tail,  on  the  dorsal  surface. 

4.  The  reproductive  and  excretory  systems  are  not  easily 
seen.  An  ovary  and  a  large  vitellarium  are  present.  The 
oviduct  opens  into  the  cloaca.  Two  long  nephridial  tubes 
open  into  a  contractile  vesicle  that  in  turn  opens  into  the 
cloaca. 

5.  There  is  a  single  ganglion  in  the  anterior  dorsal  region, 
immediately  beneath  two  red  eye  spots.  Anterior  to  the  eye 
spots  is  a  dorsal  feeler,  which  is  a  tactile  organ. 

There  are  many  common  rotifers  that  have  no  lorica  and 
some  of  them  have  the  trochal  disk  two-lobed. 

Jennings:    Rotatoria  of  the  United  States  with  Especial  Reference  to 

those  of  the  Great  Lakes.    Bull.  U.  S.  Fish  Com.,  19,  1899. 
Whitney:    The  Desiccation  of  Rotifers.    Am.  Nat.,  42,  1908. 


MOLLUSCOIDA 

Lophophore  present.     Mouth  and  anus  closely  approxi- 
mated.    Coelom  usually  present. 

Class  1.  Bryozoa  or  Polyzoa. 

Usually  colonial.  Zooids  of  small  size  and  pro- 
tected by  a  firm  cuticle. 
Subclass  1.  Entoprocta. 

Colonial  or  solitary.  Anus  and  mouth  both  in- 
side lophophore.    Epistome  present.    Tentacles 
not  retractile.     Stalk  contractile.     (Loxosoma, 
Pedicellina.) 
Subclass  2.  Ectoprocta. 

Colonial.  Anus  outside  lophophore.  Mouth 
inside  it.  Tentacles  retractile.  Stalk  not  re- 
tractile. 

Order  1.  Gymnolaemata. 

Recent,  marine.  Lophophore  circular.  Epi- 
stome absent.  (Crisia,  Bugula,  Flustrella, 
Membranipora,  Lepralia,  Schizoporella.) 

Order  2.  Phylactolaemata. 

Fresh    water.      Lophophore    horseshoe-shaped. 
Epistome  present.     (Plumatella,  Pectinatella.) 
Class  2.  Brachiopoda. 

Marine.  Solitary.  Bivalve  shell.  Usually  at- 
tached by  a  peduncle. 

Order  1.  Inarticulata. 

Valves  not  united  by  a  hinge.    (Lingula.) 

Order  2.  Articulata. 

Valves  hinged.  Usually  with  a  shelly  loop  to 
support  the  lophophore.     (Terebratulina.) 

BRYOZOA 

BUGULA  (Sp.) 

The  colonies  are  very  common  in  shallow  water  along 
shore,  attached  to  rocks  and  piles.  They  may  be  examined 
with  the  aid  of  a  glass-bottomed  pail  in  the  positions  they 
occupy  on  the  sides  of  the  piles  of  almost  any  old  wharf. 

86 


BUGULA 


87 


What  must  be  the  source  of  their  food?  What  part  of  the 
colony  is  likely  to  be  best  nourished?  Collect  specimens  by 
scraping  the  piles  and  see  what  forms  are  associated  with 
them. 

1.  Examine  a  colony  in  a  dish  of  water  and  see  how  it 
branches.     Does  it  present  any  regularity? 

Make  a  drawing  of  a  colony. 

2.  Remove  one  of  the  flat  branches,  place  it  in  a  watch 
glass  of  water,  and  examine  it  with  a  low  power.  What  more 
can  be  observed  regarding  the  branches?  How  are  the  cups 
arranged?  Are  the  cups  on  the  two  sides  of  a  twig  placed  in 
definite  relations  to  each  other?  Where  are  the  empty  cups 
found?  Explain.  Can  you  find  connections  between  the  cups 
of  the  two  sides? 

Make  a  drawing  showing  the  arrangement  of  the  cups. 

3.  Allow  a  living  branch  to  remain  undisturbed  for  a  few 
moments  and  with  a  microscope  see  how  the  thin  outer  mar- 
gins of  the  cups  are  unfolded  as  the  zooids  protrude. 

4.  Mount  a  specimen  on  a  slide,  cover,  and  compare  the 
tentacles  of  an  expanded  zooid  with  those  of  the  hydroids  that 
you  studied.  How  do  they  differ?  How  must  the  animal 
feed? 

5.  How  are  the  tentacles  arranged  around  the  distal  end 
of  the  body?  How  many  tentacles  are  there?  Look  for  the 
mouth. 

6.  Can  you  see  the  parts  of  the  alimentary  canal?  Is 
there  food  in  the  stomach?  How  does  the  zooid  pull  itself 
back  into  its  cup? 

7.  Look  for  avicularia  and  observe  their  movements  and 
structure.  Where  is  the  jaw  hinged?  Where  are  the  muscles 
that  open  it?  Where  are  the  muscles  that  close  it?  Of  these 
muscles,  which  are  largest?  Why?  See  if  "sense  hairs"  can 
be  found  between  the  jaws.    What  is  their  probable  use? 

Draw  an  avicularium. 

8.  Ooecia  with  embryos  will  be  found  in  some  specimens. 
Where  are  they  placed? 


88  MOLLUSCOIDA 

9.  Put  powdered  carmine  in  the  water  with  a  living  branch 
and  see  if  the  zooids  will  eat  it. 

10.  Put  a  small  living  branch  in  a  drop  of  sea  water  under 
a  supported  cover  glass  and  see  if  any  of  the  zooids  will  ex- 
pand. If  any  do  expand  they  may  be  examined,  with  a  high 
power,  to  good  advantage. 

Study  specimens  that  have  been  killed  while  expanded. 
Stain  with  iodine,  wash  in  water,  mount  in  glycerin,  study 
with  a  high  power.  Find  the  retractor  muscles,  the  funiculus, 
germ  cells,  and,  if  possible,  the  shape  of  the  alimentary  canal. 
As  the  alimentary  canal  bears  a  definite  relation  to  the  posi- 
tion of  the  zooid  on  the  branch,  its  shape  can  be  readily 
determined  only  when  the  branch  happens  to  be  twisted  so 
the  zooid  is  to  be  seen  in  side  view. 

Make  drawing  showing  the  structure. 

If  time  permits  study  Flustrella,  Membranipora,  Lepralia, 
or  Schizoporella,  as  type  incrusting  forms  to  determine 
methods  of  branching,  colony  formation,  how  the  apertures 
are  closed,  and  specific  characters. 

Bissonnette:    A   Method   of   Securing   Marine   Invertebrates.     Science, 

71,  1930. 
Grave:    Natural  History  of  Bugula  flabellata.    Jour.  Morph.,  49,  1930. 

PLUMATELLAi 

If  the  zooids  of  this  fresh-water  form  will  expand  in  a 
watch  glass  of  fresh  water,  notice  the  shape  of  the  lophophore 
and  the  position  of  the  epistome.  In  such  a  specimen  the 
ganglion  may  be  seen  as  a  rounded  mass  just  beneath  the 
lophophore,  between  the  mouth  and  the  anus.  Study  the 
statoblasts  with  a  microscope. 

Allman:    Monograph  of  the  Fresh-water  Polyzoa.    Ray  Soc,  1856. 
Calvet :  Contribution  a  l'Histoire  Naturelle  des  Bryozoaires  Ectoproctes 
Marins.    Trav.  Inst.  Zool.  Montpelier,  N.  S.,  Mem.  No.  8,  1900. 

Alices  of  the  large  gelatinous  form,  Pectinatella,  placed  in  watch 
glasses  of  fresh  water,  make  very  satisfactory  objects  for  study,  as  the 
zooids  will  soon  expand,  and  they  are  then  in  the  best  possible  position 
for  study. 


PLUMATELLA  TEREBRATULINA  89 

Nitsche:  Beitrage  zur  Kenntnis  der  Bryozoen.  Ueber  die  Anatomie 
und  Entwicklungsgeschichte  von  Flustra  membranacea.  Zeit.  f.  wiss. 
Zool.,  21,  1871. 

O'Donoghue,  Charles  H.,  and  Elsie  O'Donoghue:  Second  List  of  Bryozoa 
from  Vancouver  Island  Region.  Contrib.  to  Canadian  Biol,  and 
Fisheries,  N.  S.  Ill,  pp.  47-132.     (See  Bibliography  list,  1926.) 

Osburn,  T.  C:  Bryozoa  of  Woods  Hole.  Bull.  Bur.  Fish.,  xxx,  1910, 
Doc.  No.  760,  1912. 

BRACHIOPODA 

TEREBRATULINA 

Examine  specimens  on  the  demonstration  table  and  notice: 

1.  Shell.  The  difference  in  the  size  and  shape  of  the  two 
valves  and  their  position  in  relation  to  the  body.  How  are 
the  valves  articulated?    How  are  they  opened? 

2.  Peduncle.     Its  position.     What  is  its  use? 

3.  Muscles.    Those  used  in  opening  and  closing  the  shell. 

4.  Lophophore.  Consisting  of  two  elongated  arms  with  a 
double  row  of  tentacles  on  each. 

5.  Mouth.  Notice  its  relation  to  the  grooves  running  be- 
tween the  rows  of  tentacles  on  each  of  the  arms  of  the 
lophophore. 

Brooks:    Development  of  Lingula.    Ches.  Zool.  Lab.  Sci.  Results,  1878. 

Conklin:  The  Embryology  of  a  Brachiopod,  Terebratulina  septen- 
trionalis.     Proc.  Am.  Phil.  Soc,  41,  1902. 

Hancock:  On  the  Organization  of  Brachiopoda.  Trans.  Roy.  Soc,  Lon- 
don, 148,  1858. 

Morse:  Observations  on  Living  Brachiopoda.  Mem.  Bost.  Soc.  Nat. 
Hist.,  5,  1902. 


ANNELIDA 

Body  elongated,  generally  divided  into  somites.     Coelom 
usually  extensive.    Appendages  when  present  form  parapodia. 

Class  1.  Archi-annelida. 

Without  setae  or  parapodia.    Nervous  system 
not    separate    from    the    epidermis.       (Poly- 
gordius.) 
Class  2.  Chaetopoda. 

With  numerous,  distinct  somites  that  are  pro- 
vided with  setae. 
Subclass  1.  Archi-chaetopoda. 

Setae  retractile.    Nervous  system  not  separate 
from  the  epidermis.     (Saccocirrus.) 
Subclass  2.  Polychaeta. 

With  numerous  setae  per  segment.  With  a 
great  variety  of  structure.  (Amphitrite, 
Arenicola,  Autolytus,  Chaetopterus,  Clymen- 
ella,  Diopatra,  Hydroides,  Nereis,  Pectinaria, 
Polynoe,  Sabella,  Spirorbis.) 
Subclass  3.  Myzostomida. 

Disk-shaped.    Without  external  segmentation. 
Parasites  on  Echinodermata.     (Myzostoma.) 
Subclass  4.  Oligochaeta. 

Without   parapodia.     Setae    few    and   simple. 
(Tubifex,  Lumbricus.) 
Class  3.  Gephyrea. 

No    segmentation.      With    or    without    setae. 
With  introvert  or  proboscis. 
Order  1.  Inermia. 

With  introvert.  Anus  dorsal.  No  setae.    (Phas- 
colosoma.) 
Order  2.  Armata. 

With  proboscis.     Anus  posterior.     Setae  few. 
(Echiurus.) 
Class  4.  Hirudinea. 

Somites  constant  in  number,  with  more  exter- 
nal annuli  than  there  are  somites.  With  suck- 
ing mouth  and  posterior  sucker. 

90 


NEREIS  91 

Order  1.  Rhynchobdellida. 

Anterior  end  of  body  forming  a  proboscis  or 

introvert.     No  jaws.     (Glossiphonia,  Macrob- 

della,  Clepsine.) 
Order  2.  Gnathobdellida. 

No    proboscis    or    introvert.      Mouth    usually 

with  three  teeth.     (Hirudo.) 

Hatschek:    Studien  iiber  Entwicklungsgeschichte  der  Anneliden.     Arb. 

Zool.  Inst.  Wien,  1,  1878. 
Norman:    Diirfen  wir  aus  den  Reactionen  niederer  Thiere  auf  des  Vor- 

handensein  von  Schmerzempfindungen  schliessen?    Arch.  ges.  Physiol., 

67,  1897. 

CHAETOPODA 

NEREIS  VTRENS  (Clam-worm) 

These  animals  may  be  found  inhabiting  mud  flats  from 
which  the  water  flows  at  low  tide.  Occasionally  they  may  be 
seen  with  their  head  ends  protruding  from  their  burrows,  but 
generally  specimens  will  have  to  be  dug.  Notice  the  conditions 
under  which  the  animals  live  and  the  forms  with  which  they 
are  associated.  It  should  also  be  understood  that  many  of 
their  worst  enemies  are  present  only  when  the  water  covers 
their  burrows. 

External  Structure. — 1.  Examine  a  living  worm  in  a  dish 
of  sea  water,  noting  the  motions  of  the  body  and  of  the  para- 
podia  or  swimming  feet. 

2.  Is  the  general  surface  clean  or  slimy?  Compare  with 
the  earthworm  in  this  respect  and  explain  the  basis  for  the 
difference. 

3.  Determine  the  direction  of  the  peristaltic  waves  in  the 
dorsal  blood  vessel. 

4.  Is  the  median  ventral  nerve  cord  visible  through  the 
body  wall? 

5.  In  an  anesthetized  or  dead  worm,  count  the  segments  or 
metameres  and  compare  it  with  your  neighbor's  to  ascertain 
whether  the  number  is  constant.  What  segments,  if  any,  are 
devoid  of  parapodia?    Explain. 

6.  In  the  head  distinguish  the  prostomium,  which  bears 
the  four  eyes  and  a  pair  of  short  terminal  tentacles.    At  each 


92  ANNELIDA 

side  of  the  prostomium  is  a  thick  palp.  Determine  which 
parts  of  the  worm  are  most  sensitive  by  gently  stimulating 
with  a  needle. 

7.  Also  in  the  head  find  the  peristomium,  the  segment 
which  surrounds  the  mouth  and  bears  four  pairs  of  peris- 
tomial  cirri.     Stretch  the  mouth  with  forceps. 

Make  an  enlarged  drawing  of  the  head. 

8.  Hold  it  down  against  the  bottom  of  the  dish  or  place  in 
fresh  water  for  a  few  minutes  to  induce  it  to  protrude  the 
proboscis,  the  protrusible  anterior  portion  of  the  alimentary 
canal.  This  is  lined  with  chitin  and  armed  with  numerous 
denticles  and  a  pair  of  lateral  jaws. 

9.  Find  the  small  terminal  anus  and  a  pair  of  caudal  cirri 
on  the  last  segment. 

10.  With  scissors  cut  off  a  parapodium  close  to  the  body 
and  observe  that  it  has  a  dorsal  blade  and  a  ventral  blade 
{notopodium  and  neuropodium) .  Each  of  these  contains  a 
bundle  of  bristles  or  setae.  What  use  can  you  ascribe  to  the 
setae?  In  each  bundle  is  one  very  thick  seta,  the  aciculum, 
which  extends  into  the  body  and  is  attached  to  muscles.  Of 
what  use  is  the  aciculum?  Examine  a  few  of  the  small  setae 
microscopically.  What  is  their  structure?  Why  is  it  desir- 
able to  have  so  many  of  the  small  setae?  Can  you  give  any 
reason  for  Nereis  having  more  setae  than  the  earthworm? 

Observe  that  each  parapodium  has  a  small  dorsal  and  a 
small  ventral  cirrus,  and  that  the  main  portion  of  both  noto- 
podium and  neuropodium  has  the  form  of  a  flattened  blade, 
somewhat  divided  into  lobes.  The  largest  lobe  of  the  noto- 
podium is  very  thin  and  vascular.  What  function  can  you 
ascribe  to  it? 

Draw  a  parapodium. 

11.  Look  for  the  nephridiopores,  minute  apertures  which 
are  segmentally  placed  on  the  ventral  surface  near  the  neuro- 
podial  cirri. 

Internal  Structure. — For  dissection  use  a  specimen  that 
has  been  killed  and  fasten  it  down  by  a  pin  through  the  head 


NEREIS  93 

and  one  through  the  posterior  part.    With  scissors  cut  through 
the  body  wall,  longitudinally,  near  the  mid-dorsal  line. 

A  preserved  specimen  can  easily  be  segmented  trans- 
versely with  a  sharp  razor  at  the  somatic  boundaries.  These 
sections  are  valuable  for  comparison  during  dissection. 

Find  the  septa  which  divide  the  coelom,  or  body  cavity, 
into  metameric  chambers.  Cut  through  the  septa  with  scis- 
sors and  pin  the  edges  of  the  body  wall  apart,  progressing 
toward  the  head. 

Circulatory  System. — The  dorsal  blood  vessel  lies  along 
the  dorsal  surface  of  the  alimentary  canal  and  gives  off 
branches  in  each  segment,  which  ramify  through  the  body 
wall  and  viscera  and  connect  with  the  longitudinal,  ventral 
blood  vessel.  The  blood  plasma  contains  hemoglobin  in  solu- 
tion. 

Digestive  System. — The  buccal  cavity  leads  into  a  mus- 
cular pharynx.  The  eversible  buccal  region  and  the  protru- 
sible  pharynx  form  the  proboscis.  Examine  carefully  the 
muscles  of  the  pharynx,  protractors  and  retractors,  and  as- 
certain their  attachments.  Posterior  to  the  pharynx  find  a 
small  dilation  and  a  narrow  esophagus  with  a  digestive  gland 
at  each  side.  Where  does  the  duct  of  the  gland  open?  In 
the  very  long  stomach-intestine  note  the  constrictions  and 
their  relations  to  the  dissepiments.  Can  you  demonstrate 
dorsal  or  ventral  mesenteries?  Cut  open  the  pharynx  and 
the  anterior  end  of  the  stomach-intestine  and  note  the  char- 
acter of  their  walls. 

Make  a  drawing  of  the  digestive  system. 

Muscular  System. — How  many  distinct  bands  of  longi- 
tudinal muscles  can  be  distinguished?  Examine  with  a  hand 
lens  the  parapodial  muscles  attached  to  the  base  of  the 
acicula.  Can  you  make  out  a  layer  of  circular  muscles?  Of 
what  layers  does  the  body  wall  consist? 

Excretory  System. — The  nephridia  are  not  nearly  so 
easily  found  or  studied  as  they  are  in  the  earthworm.  Near 
or  just  beneath  the  lateral  edges  of  the  ventral  muscle  bands 


94  ANNELIDA 

find  the  minute  pear-shaped  nephridia.  Determine  their  dis- 
tribution in  the  body.  Each  nephridium  consists  of  a  tor- 
tuous canal  in  a  multinucleate  mass  of  protoplasm.  The 
external  opening  is  the  nephridiopore  above  mentioned.  The 
inner  end  perforates  the  septum  anterior  to  the  body  of  the 
nephridium  and  opens  into  the  coelomic  cavity  of  the  seg- 
ment next  in  front,  by  a  ciliated  funnel,  the  nephrostome. 
With  a  hand  lens  try  to  find  the  nephrostome.  Remove  a 
nephridium  by  means  of  fine  forceps  and  examine  it  with  a 
microscope. 

Reproductive  System. — The  sexes  are  separate,  but  no 
permanent  gonads  are  present.  At  the  breeding  season  the 
ova  or  spermatozoa  are  proliferated  from  the  coelomic  ep- 
ithelium of  a  large  number  of  segments  and  escape  by  rup- 
ture of  the  body  wall. 

Nervous  System.1 — On  lifting  the  alimentary  canal  you 
will  see  the  ventral  ganglionated  nerve  cord.  Note  the  nerves 
passing  off  laterally  from  the  ganglia.  How  many  pairs  of 
nerves  per  segment  are  there,  and  how  are  they  placed?  Are 
the  ganglia  metameric?  Is  there  any  indication  that  the 
nerve  cord  is  double?  At  the  anterior  extremity  of  the  cord 
note  the  infra-esophageal  ganglia  and,  extending  from  them 
and  encircling  the  anterior  end  of  the  alimentary  canal,  the 
circumesophageal  connectives  which  unite  above  in  the  bi- 
lobed  brain  or  supra-esophageal  ganglia.  Sensory  nerves  con- 
nect the  brain  with  the  eyes,  tentacles,  and  palps. 

Make  a  drawing  of  the  nervous  system. 

Binard  et  Jeener:    Morphologie  du  lobe  preoral  des  polychaetes.    Inst. 
Zool.  Torley-Rousseau  Recueil  (Bruxelles),  2,  1928. 

1  The  nervous  system  can  be  most  readily  studied  by  tearing  it  out 
with  needles  in  a  specimen  which  has  been  macerated  in  20  per  cent 
nitric  acid  for  twenty-four  hours.  Sensory  cells  and  their  neurites  can 
be  identified  in  the  parapodia  by  placing  them  in  a  1  per  cent  solution 
of  ammonium  picrate  after  having  let  vigorous  worms  crawl  around  for 
three  or  four  hours  in  a  small  amount  of  1  per  cent  solution  of  meth- 
ylene-blue.  Mounts  of  the  parapodia  should  be  made  in  a  mixture  of 
glycerin  and  ammonium  picrate  solution. 


NEREIS,   AUTOLYTUS  95 

Copeland  and  Wieman:    The  Chemical  Sense  and  Feeding  Behavior  of 
Nereis  virens.    Biol.  Bull.,  vol  xlvii,  No.  4,  October,  1924. 

Just:    An  Experimental  Analysis  of  Fertilization  in  Platynereis  mega- 
lops.  Biol.  Bull.,  28,  1915. 

:    Breeding  Habits  of  the  Heteronereis  Form  of  Heteronereis  mega- 
lops  at  Woods  Hole.    Biol.  Bull.,  27,  1914. 

A  Cytological  Study  of  Effects  of  Ultra-violet  Light  on  the  Egg 


of  N.  limbata.    Zeit.  Zellforsch.,  17,  1933. 
Lillie:    Studies  of  Fertilization  in  Nereis.    I.  and  II.  Jour.  Morph.,  22, 

1911.     III.  and  IV.  Jour.  Exp.  Zool.,  12,  1912.     V.  Jour.  Exp.  Zool., 

14,  ms. 
Lillie  and  Just:    Breeding  Habits  of  the  Heteronereis  Form  of  Nereis 

limbata  at  Woods  Hole^Mass.    Biol.  Bull.,  24,  1913. 
Martin:     Polymorphism    and    Asexual    Reproduction    in    Dodecaceria. 

Biol.  Bull.,  65,  1933. 
Mayer:    The  Annual  Breeding-swarm  of  the  Atlantic  Palolo.    Carnegie 

Inst.  Pub.,  102,  1908. 
Sayles:   Effects  of  Salinity  Changes  on  Body  Weight  of  N.  virens.    Biol. 

Bull.,  69,  1935. 
Wilson,   E.  B.:     The   Cell-lineage   of  Nereis.     A   Contribution   to   the 

Cytology  of  the  Annelid  Body.    Jour.  Morph.,  6,  1892. 
Woodworth:     The   Palolo   Worm,   Eunice   viridis.     Bull.   Mus.   Comp. 

Zool.,  Harvard,  51,  1907. 

AUTOLYTUS  CORNUTUS 

This  polychaete  lives  in  cylindrical  tubes  of  its  own  con- 
struction that  it  attaches  to  seaweeds  and  hydroids,  and  is 
especially  interesting  because  of  its  method  of  reproduction, 
by  budding. 

Study  live  and  preserved  specimens  with  the  naked  eye 
and  with  the  hand  lens,  in  order  to  form  a  correct  idea  of  its 
natural  color,  size,  and  movements,  and  then  study  stained 
specimens  with  the  low  power. 

1.  Observe  two  individuals  attached  end  to  end.  The 
anterior  one  is  a  nonsexual  zooid  ^ (or  original  "stock")  and 
is  giving  rise  to  a  new  sexual  zooid  by  budding.  Counting 
the  peristomium  as  one  somite,  on  what  somite  does  the  bud 
begin  and  what  does  it  represent? 

2.  Study  the  head  of  the  anterior,  nonsexual  zooid.  Find 
three  prostomial  tentacles.  How  are  they  arranged?  Find 
the  eyes.    How  many  pairs  are  there?    Do  you  find  palps? 


96  ANNELIDA 

On  the  peristomium  find  the  two  tentacles  and  a  tentacular 
cirrus  on  each  side. 

3.  On  the  succeeding  somites  study  the  parapodia.  Ob- 
serve the  large  dorsi  cirri  and  the  knoblike  notopodium 
with  the  short  unjointed  setae.     There  is  no  neuropodium. 

4.  Identify  the  pharynx,  gizzard,  and  intestine. 

5.  Compare  the  sexual  bud  with  the  nonsexual  individual. 
The  adult  male  and  female  differ.  The  outer  prostomial 
tentacles  of  the  male  are  forked.  Is  this  bud  to  be  a  male 
or  a  female?  In  an  older  sexual  individual  make  out  a  so- 
called  thoracic  region  in  which  the  setae  are  short,  and  an 
abdominal  region  in  which  the  setae  are  long.  Look  for  evi- 
dences of  germ  cells  in  the  body  cavity,  between  the  intestine 
and  body  wall.  There  is  a  ventral  brood  pouch  on  the  adult 
female  and  the  young  partly  develop  in  it.  Find  the  anal 
cirri. 

A  drawing  illustrating  the  method  of  reproduction  should 

be  made. 

LEPIDONOTUS  (POLYNOE)  SQUAMATUS 

The  family  Aphroditidae,  to  which  this  belongs,  can  be 
distinguished  from  all  others  by  the  presence  of  peculiar 
plates  (elytra)  on  the  dorsal  surface.  They  lead  sluggish 
lives  under  stones  and  are  carnivorous.  Note  the  size,  color, 
and  shape  of  the  worm. 

1.  Examine  the  elytra.  How  are  they  arranged?  What 
purpose  do  they  serve?  How  many  are  there?  With  a  hand 
lens  observe  the  fringed  condition  of  the  outer  edge  and  the 
small  tubercles  covering  the  surface.  Note  the  color  of  the 
elytra  and  the  notches  in  the  inner  edges  of  the  posterior  pair. 

Remove  with  forceps  all  of  the  elytra  on  one  side  of  the 
specimen  and  the  first  two  or  three  on  the  other  side.  Note 
the  stumps  to  which  the  elytra  were  joined.  Do  all  seg- 
ments have  elytra?  If  not,  do  the  scaleless  segments  have 
structures  which  correspond  to  elytra? 

2.  Examine  the  dorsal  aspect  of  the  head,  and  note  the 
small  prostomium,  with  two  pairs  of  eyes,  three  slender  ten- 


LEPIDONOTUS  97 

tacles,  and  a  pair  of  fleshy  palps.  Outside  the  palps  are  two 
pairs  of  cirri  arising  from  the  peristomium.  The  significance 
of  these  will  be  understood  later. 

3.  Find  the  mouth,  placed  ventrally  in  the  first  or  per- 
istomial  somite.  The  mouth  leads  into  a  buccal  region,  which 
is  eversible  and  fringed  at  the  end  with  papillae,  each  having 
a  dark  spot  at  the  base.  If  the  pharynx  is  retracted,  expose 
the  buccal  cavity  by  a  median  ventral  incision.  In  the  an- 
terior end  of  the  pharynx  are  four  black  chitinous  jaws.  Do 
you  infer  that  this  species  is  carnivorous  or  herbivorous? 
The  eversible  buccal  region  and  the  protrusible  pharynx  form 
the  proboscis. 

4.  The  anus  is  dorsally  placed,  and  can  be  found  beneath  . 
the  notches  in  the  last  pair  of  elytra. 

5.  Examine  the  lateral  appendage  or  parapodium  of  the 
third  or  any  subsequent  somite.  Note  that  it  consists  of  a 
stout  ventral  or  neuropodial  division,  and  a  less  prominent 
dorsal  or  notopodial  division,  each  supported  internally  by 
a  chitinous  rod  or  aciculum,  and  bearing  externally  a  tuft 
of  setae.  If  there  is  time,  compare  the  form  of  the  noto- 
podial and  neuropodial  setae.  The  typical  parapodial  struc- 
ture is  completed  by  a  soft  neuropodial  cirrus  ventrally,  and 
a  notopodial  cirrus  dorsally.  Did  you  find  any  evidence  that 
the  elytra  are  modified  notopodial  cirri? 

6.  Make  a  careful  study  of  the  appendages  of  the  first  or 
peristomial  and  the  last  or  anal  segment.  Cut  off  close  to 
the  body,  mount  in  glycerin,  and  examine  with  low  power  of 
the  microscope.  Determine  the  homology  of  the  parts  ob- 
served. 

Draw  the  dorsal  aspect  of  the  ^head,  to  show  the  appen- 
dages and  the  proboscis,  if  exposed.  Diagram  the  structure 
of  the  parapodium  as  seen  in  a  transverse  section  of  the  body. 

Unlike  most  other  worms,  many  of  the  Aphroditidae  have 
a  fixed  number  of  somites.  Count  the  number  in  your  speci- 
men, including  in  the  enumeration  the  peristomial  and  anal 
segments.  How  many  pairs  of  elytra?  The  number  and  po- 
7 


98  ANNELIDA 

sition  of  the  elytra  are  also  characteristic  of  various  genera, 
and  may  be  conveniently  represented  by  an  elytral  formula 
consisting  of  the  numbers  of  the  somites  on  which  elytra  are 
borne,  e.  g.,  2,  4,  5,  etc.  Determine  the  elytral  formula  of 
your  specimen.  Draw  one  of  the  elytra,  noting  its  form, 
surface,  and  border  markings,  etc.  These  points  are  of  im- 
portance in  defining  species.  Each  of  the  last  pair  of  elytra 
is  notched  on  the  medium  side  over  the  anus,  which  in  this 
form  opens  dorsally  instead  of  terminally. 

DIOPATRAICUPREA 

This  worm  belongs  to  the  family  Eunicidae.  Specimens 
live  on  mud  and  sand  flats,  sometimes  above  low-tide  mark, 
but  usually  where  the  burrows  are  covered  by  water.  This 
form  is  especially  interesting  because  of  its  feeding  and  tube- 
building  habits,  parapodial  gills,  and  complex  jaw  apparatus. 
Study  the  preserved  specimens  for  the  structure  and  speci- 
mens in  an  aquarium  for  the  habits. 

Make  a  special,  comparative  study  of  the  reactions  of 
Nereis  and  Diopatra.  What  types  of  movements  can  you 
distinguish?  What  is  the  significance  of  each?  Which  worm 
is  better  adapted  for  a  pelagic  life?  Locate  any  respiratory 
structures  which  may  be  present.  What  structural  differences 
can  you  see  which  may  be  correlated  with  different  habits? 
Place  a  glass  tube  in  the  dish  with  a  worm  and  gently  move 
the  head  of  the  worm  so  that  the  anterior  end  projects  into 
the  tube.  Observe  results.  Study  the  activities  of  a  worm 
after  it  has  been  in  the  tube  a  few  minutes.  Are  these  iden- 
tical with  the  movements  of  the  worm  when  free  in  the 
water?  Supply  a  Diopatra  in  a  glass  tube  with  bits  of  sea 
weed  or  shells  and  observe  the  method  of  tube  formation. 

1.  Notice  the  size  of  the  body,  also  its  gradual  attenua- 
tion posteriorly.  Account  for  this  condition.  Observe  how 
degenerate  the  posterior  parapodia  are  from  the  same  cause. 

2.  The  prostomium.  Identify  the  tentacles.  What  is 
their  number  and  arrangement?    Find  a  pair  of  eyes  dorsally 


DIOPATRA,    CHAETOPTERUS  99 

placed  behind  the  tentacles,  also  a  pair  of  palps  in  front  of 
them.  Note  a  second,  larger  pair  of  palps  which  serve  as  an 
upper  lip. 

3.  The  peristomiwn.  What  appendages  does  it  carry? 
Note  the  lower  lip  formed  from  the  ventral  edge  of  the  per- 
istomium. 

4.  The  position  of  the  jaw  apparatus  can  be  identified  as 
being  in  a  pouch  ventral  to  the  buccal  region.  Find  both  by 
means  of  a  probe.  What  kind  of  food  are  such  jaws  fitted 
for? 

5.  The  parapodia  vary  greatly,  depending  upon  their  po- 
sition on  the  body.  Notice  that  the  notopodia  are  vestigial, 
being  represented  only  by  the  dorsal  cirri  and,  toward  the 
anterior  end,  branchial  cirri  or  gills.  Acicula  can  be  seen 
projecting  into  the  base  of  the  dorsal  cirrus.  The  neuro- 
podium  shows  two  kinds  of  setae:  (a)  stiff  and  unjointed, 
(6)  crochets.  It  also  bears  an  accessory  cirrus  and  the  ven- 
tral cirri,  which  are  curiously  modified  in  most  cases  as  glands 
for  use  in  tube  building.  Make  out  all  these  modifications 
and  where  they  occur. 

CHAETOPTERUS 

This  is  one  of  the  most  aberrant  of  our  Polychaeta.  It 
lives  on  mud  flats  below  low  tide  in  a  U-shaped,  parchment- 
like tube  both  ends  of  which  protrude  above  the  mud.  In 
the  body  three  regions  can  be  distinguished.  Examine  a  tube 
and  see  the  size  of  its  outer  openings.  Specimens  may  be 
made  to  live  in  tubes  of  glass,  bent  to  correspond  to  their 
tubes,  and  their  normal  movements  may  thus  be  studied  in 
aquaria.    What  must  be  the  source^  of  the  animal's  food? 

1.  The  anterior  region.  Identify  ten  modified  parapodia, 
the  fourth  of  which  is  supplied  with  a  group  of  much  stouter 
setae.  Observe  that  the  tunnel-like  mouth  is  placed  dorsally 
and  surrounded  ventrally  and  laterally  with  flaring  peris- 
tomial  lips.  Find  the  pair  of  peristomial  cirri.  The  region 
between  these  cirri  represents  the  prostomium. 


100  ANNELIDA 

2.  The  iniddle  region  consists  of  five  somites.  The  first, 
the  eleventh  segment,  is  marked  by  the  great  pair  of  wings 
which  are  used  to  bring  food  to  the  mouth.  Their  dorsal  sur- 
faces are  grooved  and  supplied  with  cilia,  as  is  the  median 
dorsal  line.  Hence  a  current  of  water  passes  continually  to- 
ward the  mouth.  The  twelfth  somite  is  marked  by  a  dorsal 
and  a  ventral  sucker,  which  are  modified  parapodia.  Somites 
thirteen,  fourteen,  and  fifteen  carry  notopodial  folds  or  fans, 
for  keeping  up  a  stream  of  water  through  the  tube.  Their 
neuropodia  are  mere  knobs. 

3.  The  posterior  region  is  less  highly  modified.  Of  how 
many  segments  does  it  consist?  Notice  their  gradual  diminu- 
tion in  size.    Homologize  the  parts  of  their  appendages. 

4.  The  living  Chaetopterus  contains  a  green  coloring  mat- 
ter and  is  very  luminescent. 

5.  The  eggs  are  orange  yellow  and  the  sperm  milky 
white.    Determine  their  location.    The  sexes  are  separate. 

A  drawing  is  desirable. 

Lillie:    Observations  and  Experiments  Concerning  the  Elementary  Phe- 
nomena   of   Embryonic   Development    in   Chaetopterus.     Jour.    Exp. 

Zool.,  3,  1906. 

AMPHITRITE  ORNATA 

This  belongs  to  the  family  Terebellidae  and  lives  under 
stones,  or  in  mud  or  sand,  along  shore  in  stout  muddy  tubes. 

1.  Find  the  prostomium,  which  forms  an  upper  lip  and 
bears  a  transverse  group  of  long,  retractile  tentacles. 

2.  The  peristomium,  forms  the  under  lip,  but  bears  no  ap- 
pendages. 

3.  Find  three  pairs  of  racemose  gills.  These  are  modifi- 
cations of  the  dorsal  cirri. 

4.  Notice  again  the  feeble  development  of  the  parapodia 
and  the  absence  of  ventral  cirri  and  neuropodial  setae.  Setae 
are   not   found   posteriorly.     Exactly   which   segments    have 

setae? 

5.  Find  the  ventral  shield  glands  which  are  concerned  in 
building  the  tube.    How  many  are  there? 


AMPHITRITE,    CISTENIDES,    CLYMENELLA  101 

6.  The  live  worm  is  of  a  bright  pinkish  color,  due  to  its 
red  blood.  There  is  only  one  internal  septum  and  its  forms 
a  so-called  diaphragm.  Anterior  to  the  diaphragm  the 
nephridia  are  large  and  excretory  in  function.  Posterior  to 
the  diaphragm  the  nephridia  serve  as  genital  tubes. 

A  drawing  is  desirable. 

CISTENIDES  (PECTINARIA)  GOULDI 

This  very  aberrant  worm  belongs  to  the  family  Amphic- 
tenidae. 

1.  Study  the  beautiful  tube  of  sand  and  the  manner  in 
which  the  grains  are  fitted  together.  It  is  said  that  the 
worms  can  carry  the  tubes  about. 

2.  See  how  the  peristomium  and  the  large  golden  setae 
close  the  shell.  The  setae  are  said  to  belong  to  the  second 
somite.  Notice  the  ends  of  the  tentacles  protruding  from  the 
tube. 

3.  Find  the  tentacles,  two  pairs  of  gills,  and  the  para- 
podia.  Notice  how  the  latter  diminish  in  size  posteriorly  and 
how  each  typically  consists  of  a  ridge-like  notopodium  with- 
out setae  and  a  reduced  neuropodium  with  long  golden  setae. 
If  the  specimen  is  complete  you  can  see  a  much  degenerated 
portion  (the  scapha)  at  the  posterior  end,  which  serves  to 
close  the  small  end  of  the  tube. 

A  drawing  is  desirable. 

CLYMENELLA  TORQUATA 

This  worm  belongs  to  the  family  Maldanidae.  It  makes 
tubes  of  sand  and  generally  lives  in  sheltered  places  on  sandy 
or  muddy  shores. 

1.  Study  the  structure  of  the  tube. 

2.  Observe  the  diameter  and  length  of  the  worm,  the  small 
number  of  somites,  their  great  length  as  compared  with 
somites  of  Nereis,  and  the  reduced  parapodia.  How  many 
segments  are  there?  Which  are  setigerous?  Notice  the 
characteristic  collar  on  the  fifth  somite,  and  the  funnel  at 
the  posterior  end,  with  the  anus  within  it.     The  mouth  is 


102  ANNELIDA 

more  or  less  ventral  and  is  overhung  by  a  narrow  prostomium 
surrounded  by  a  peristomial  rim. 
A  drawing  is  desirable. 

Sayles:     External   Features   of   Regeneration  in   Clymenella   torquata. 

Jour.  Exp.  Zool.,  62,  1932. 
:    Regeneration  in  the  Polychaete  Clymenella  torquata.     Physiol. 

Zool.,  7,  1934. 

ARENICOLA^CRISTATA  (Lug-worm) 

This  worm  lives  in  sand  flats  in  U-shaped  burrows.  Dur- 
ing the  breeding  season  the  burrows  of  females  may  be  lo- 
cated by  the  large,  elongated,  gelatinous  egg  masses. 

External  Structure. — 1.  Examine  a  living  worm,  noting 
its  movements.  Are  they  associated  with  locomotion?  Com- 
pare with  Nereis  and  Amphitrite.  What  is  the  effect  of  the 
tube  habit  on  locomotion?  Compare  the  general  shapes  of 
Arenicola,  Amphitrite  and  Nereis.  In  what  respects  are  the 
shapes  of  the  first  two  similar?  How  do  you  account  for 
this?  Is  the  color  of  Arenicola  a  pigment  or  is  it  due  to 
iridescence? 

2.  On  the  head  locate  the  prostomium,  a  small,  three- 
lobed  structure  embedded  in  the  dorsal  surface  of  the  first 
segment  or  peristomium.  Unless  the  specimen  has  been  well 
narcotized,  the  prostomium  will  be  withdrawn  into  the  nuchal 
groove,  which  lies  just  posterior  to  it.  Prostomial  tentacles 
and  palps  are  absent.  Compare  with  Amphitrite.  Eyes  are 
present  as  minute,  subepidermal  structures  not  visible  ex- 
ternally. 

3.  The  body  is  divisible  into  three  regions:  an  anterior 
one  bearing  parapodia  but  no  gills ;  a  middle  one  bearing  both 
parapodia  and  gills;  a  posterior  one  bearing  neither. 

4.  Examine  a  parapodium  and  find  both  notopodium  and 
neuropodium.  Explain  the  position  of  the  gills  so  near  the 
dorsal  surface.  Compare  with  Amphitrite.  Examine  setae 
from  both  divisions  of  the  parapodium.  In  the  posterior  re- 
gion of  the  body  note  the  small  papillae  which  occur  on  the 
fourth  annulus  and  are  probably  vestigial  parapodia. 


ARENICOLA 


103 


5.  Locate  the  anterior,  terminal  mouth  and  posterior, 
terminal  anus. 

6.  Nephridiopores,  situated  just  ventral  to  the  neuropodia 
of  the  fifth  to  tenth  setigerous  segments  are  not  easily  visible 
under  ordinary  conditions. 

7.  Study  the  segmentation  of  the  worm  and  note  that  the 
annuli  and  segments  are  not  homologous.    Where  parapodia 


Relation  of 

Segments 

ro  Various  Other  Structures 

Annuli. 

Gills. 

Nephridia. 

Gonads. 

Segments. 

Number  per 
segment. 

One  on  which 
setae  found. 

Septa. 

1st 

1 

no  setae 

2nd 

2 

no  setae 

<             1st 

3rd 

2 

1st 

4th 

3 

2nd 

< 2nd 

5th 

4 

3rd 

< 3rd 

6th 

5 

4th 

7th 

5 

4th 

... 

1st 

8th 

5 

4th 

2nd 

1st 

9th 

5 

4th 

1st 

3rd 

2nd 

10th 

5 

4th 

2nd 

4th 

3rd 

11th 

5 

4th 

3rd 

5th 

4th 

12th 

5 

4th 

4th 

6th 

5th 

13th 

5 

4th 

5th 

14th 

5 

4th 

6th 

15th 

5 

4th 

7th 

16th 

5 

4th 

8th 

... 

17th 

5 

4th 

9th 

18th 

5 

4th 

10th  , 

19th 

5 

4th 

11th 

20th 

5 

no  setae 

21st 

5 

no  setae 

22nd 

5 

no  setae 

etc. 

5 

no  setae 

* 

*  Septa  begin  again  in  extreme  posterior  part  of  worm.    There  are  dorsal  and  ventral  mesenteries 
in  the  3rd  and  4th  segments. 


104  ANNELIDA 

are  present  they  offer  a  clue  to  the  number  of  segments,  since 
there  is  ordinarily  one  pair  of  parapodia  per  segment.  Where 
parapodia  are  absent,  internal  structures  (e.  g.,  septa)  may 
help  to  define  segments.    See  table  on  page  103. 

Internal  Structure. — If  fresh  material  is  used,  anesthetize 
first  in  8  per  cent  alcohol  in  sea  water.  Pin  the  specimen 
out  in  a  dissecting  pan,  dorsal  side  up,  sticking  two  pins 
through  the  sides  of  the  first  segment  and  two  through  the 
sides  of  the  tail  region.  Cover  the  specimen  with  water. 
Open  the  worm  by  making  an  incision  with  a  fine  pair  of 
scissors  in  the  mid-dorsal  region  near  the  center  of  the  gill- 
bearing  portion.  Before  continuing  with  the  cut,  notice  the 
coelomic  fluid.  Examine  some  of  this  under  the  microscope. 
Observe  the  coelomic  corpuscles  and  possibly  the  reproduc- 
tive cells.  There  are  two  kinds  of  coelomic  corpuscles: 
amoebocytes  and  fusiform  cells.  These  cells  form  clots  when 
removed  from  the  coelom.    They  are  also  phagocytic. 

Next  raise  the  point  of  incision  carefully  with  forceps  and 
extend  it  to  within  an  eighth  of  an  inch  of  the  prostomium. 
Posteriorly  continue  the  cut  about  an  inch  into  the  tail  re- 
gion. The  tail  region  is  difficult  to  open  and,  unless  you  are 
careful,  you  may  pierce  the  intestine.  The  flaps  of  the  body 
wall  should  now  be  pinned  out  right  and  left  so  that  the  worm 
is  moderately  well  stretched  both  longitudinally  and  trans- 
versely. At  the  breeding  season  ova  or  spermatids  are  so 
abundant  that  they  may  obscure  some  of  the  organs.  In 
this  case  the  reproductive  cells  should  be  carefully  washed 
away. 

Note  that  the  septa  are  confined  to  the  anterior  and  pos- 
terior regions  of  the  body.  On  the  anteriormost  septum  there 
is  a  pair  of  diaphragmatic  pouches,  which  extend  posteriorly. 
It  is  possible  that  these  may  have  some  function  in  connec- 
tion with  the  extension  of  the  proboscis.  What  advantage 
is  there  in  the  absence  of  septa  throughout  the  principal  part 
of  the  worm? 

Digestive    System. — The    protrusible   proboscis   region    is 


ARENICOLA  105 

followed  by  an  esophagus  which  extends  through  several  seg- 
ments. At  the  junction  of  esophagus  and  stomach  note  the 
two  conical,  yellowish  esophageal  glands.  The  stomach  is 
covered  with  a  vascular  gastric  plexus  between  the  branches 
of  which  is  the  yellow  chlorogogue  tissue.  When  you  have 
finished  all  dissection,  observation  and  drawing,  slit  open  the 
alimentary  canal  and  locate  the  ventral  ciliated  groove. 

Vascular  System. — There  is  a  closed  blood  system.  The 
general  course  of  the  circulation  is  anteriorly  in  the  dorsal 
and  longitudinal  intestinal  vessels  and  posteriorly  in  the  ven- 
tral vessel.     The  principal  vessels  are: 

1.  Dorsal  Blood  Vessel. — Arises  near  anus,  extends  along 
dorsal  side  of  intestine  and  terminates  in  small  vessels  on 
esophagus.     It  communicate  with  the  following: 

(a)  Intestinal  Vessels. — One  pair  in  each  posterior  seg- 
ment, more  numerous  on  anterior  part  of  intestine. 

(b)  Efferent  Branchial  Vessels. — From  last  seven  pairs  of 
gills. 

(c)  Gastric  Plexus. — Numerous  vessels  over  wall  of 
stomach. 

(d)  Nephridial  Vessels. — To  first  three  nephridia. 

(e)  Esophageal  Pouch  Vessel. 

(/)  Septal  Vessels. — To  second  and  third  septa. 

2.  Ventral  Blood  Vessel. — Arises  by  fusion  of  small  ves- 
sels at  anterior  end  of  body.  It  communicates  with  the  fol- 
lowing: 

(a)  Septal  Vessels. — From  the  first  three  septa  and  the 
diaphragmatic  pouches.  Branches  of  second  and  third  septal 
vessels  connect  with  the  neural  vessels  (see  p.  106).  There 
is  also  a  connection  between  ventral  and  each  neural  at  level 
of  second  setigerous  sac. 

(b)  Segmental  Vessels. — One  pair  per  segment,  associated 
with  the  setigerous  sacs  and  with  the  nephridia  and  gills 
where  the  two  latter  are  present. 

(c)  Intestinal  Vessels. — To  intestinal  wall. 

3.  Subintestinal    Vessels. — A    pair   running   most   of   the 


106  ANNELIDA 

length  of  the  stomach.  These  communicate  with  the  gastric 
plexus  and  receive  the  efferent  branchial  vessels  from  the 
first  four  pairs  of  gills. 

4.  Lateral  Gastric  Vessels. — One  on  each  side  receives 
blood  from  the  gastric  plexus.  They  are  clearly  distinguish- 
able only  on  the  anterior  half  of  the  stomach.  Each  com- 
municates anteriorly  with  a  heart. 

5.  Hearts. — Paired  structures,  located  laterally  on  each 
side  of  anterior  end  of  stomach.  Each  consists  of  an  auricle 
and  a  ventricle.  Each  auricle  is  really  a  swelling  at  the  an- 
terior end  of  a  lateral  gastric  vessel.  The  auricle  gives  off 
anteriorly  a  lateral  esophageal  vessel  as  well  as  discharging 
into  the  ventricle.  The  ventricle  sends  blood  into  the  ventral 
blood  vessel. 

6.  Neural  Vessels. — One  runs  along  each  side  of  ventral 
nerve  cord.  They  arise  in  capillaries  at  the  anterior  end  of 
the  body.  Each  communicates  with  the  ventral  vessel  in 
segments  two  to  six,  inclusive. 

7.  Nephridial  Longitudinal .  Vessels. — Lie  just  ventral  to 
nephridiopores,  one  on  each  side  of  the  body.  Each  runs  the 
length  of  the  region  where  nephridia  are  found. 

8.  Dorsal  Longitudinal  Vessels. — One  on  each  side  run- 
ning parallel  to  the  nephridial  longitudinal  but  dorsal  to  the 
level  of  the  notopodial  sacs. 

9.  In  each  setigerous  segment  there  is  a  ring  of  blood  ves- 
sels formed  by  the  connectives  between  the  neurals,  nephridial 
longitudinals  and  dorsal  longitudinals.  These  vessels  can 
best  be  seen  in  young,  transparent  worms. 

Muscular  System. — Note  the  conspicuous  bands  of  longi- 
tudinal muscles.  External  to  these  are  the  circular  muscles 
which  can  be  seen  only  if  some  of  the  longitudinal  layer  is 
teased  away  carefully.  Inside  these  muscles  are  the  oblique 
muscles  which  consist  of  many  bands  which  pass  from  the 
midventral  region  to  the  dorsolateral  part  of  the  body  wall 
on  each  side.  Associated  with  each  setigerous  sac,  there  are 
six  to  ten  protractor  muscles,  which  are  attached  to  the  dorso- 


ARENICOLA,    PARASABELLA  107 

lateral  body  wall,  and  a  single  retractor  muscle,  which  has 
its  origin  on  the  midventral  body  wall. 

Nephridia. — Location?  Number?  To  see  them  clearly, 
cut  the  oblique  muscles.  With  a  hand  lens,  distinguish  the 
funnel  with  its  fringed  dorsal  lip  and  its  simple  ventral  lip. 
The  excretory  tubule  is  divided  into  an  excretory  portion  and 
a  bladder.  The  latter  communicates  with  the  outside  through 
the  nephridiopore. 

Gonads. — Each  is  a  minute  body  attached  to  the  posterior 
margin  of  the  lip  of  the  nephridial  funnel.  They  occur  on 
the  last  five  pairs  of  nephridia.  The  reproductive  cells  are 
discharged  to  the  outside  through  the  nephridia. 

Nervous  System. — Push  aside  the  digestive  tract  and  fol- 
low the  ventral  nerve  cord  forward  to  the  first  septum.  The 
brain  and  circumesophageal  connectives  can  be  found  more 
easily  when  the  proboscis  has  been  completely  retracted. 
Remove  the  pins  at  the  anterior  end,  pull  in  the  proboscis 
with  a  pair  of  forceps,  and  then  pin  the  specimen  down  again. 
Usually  an  otocyst  can  be  found  on  each  side  attached  to 
the  connective  about  one  third  of  the  way  from  brain  to  ven- 
tral nerve  cord. 

Ashworth:     Arenicola    (the    Lug-worm).     Liverpool    Mar.   Biol.   Com. 

Mem.,  11,  1904. 
Gamble  and  Ashworth:    The  Anatomy  and  Classification  of  the  Areni- 

colidae  with  Some  Observations  on  their  Post-larval  Stages.     Quart. 

Jour.  Mic.  Sci.,  43,  1900. 
Strunk:    Excretions-Physiologie  der  Polychaten  Arenicola  marina  und 

Stylaroides  plumosus.     Zool.  Jahrb.,  Abt.  Allgem.  Zool.  u.   Physiol. 

Tiere,  47,  1930. 

PARASABELLA  MICROPHTHALMA 

This  worm  belongs  to  the  family  Sabellidae.  It  builds 
leathery,  muddy  tubes  on  piles,  among  tunicates,  algae,  etc. 

1.  In  addition  to  the  general  size,  form,  and  color  of  the 
worm,  observe  the  reduced  condition  of  the*  parapodia,  and 
the  arrangement  and  general  structure  of  the  branchiae  or 
gills.  These  structures  are  modifications  of  the  palps  and 
not  of  the  parapodia,  as  in  the  other  species  which  have  been 


108  ANNELIDA 

studied.  Observe  the  two  irregular  rows  of  small  ocelli  or 
eye  spots.  Account  for  the  presence  of  eyes  in  their  position. 
A  pair  of  short  tentacles  can  be  seen  by  pushing  the  branchiae 

aside. 

2.  Find  a  collar  which  is  used  in  smoothing  the  orifice  of 
the  tube.  This  is  a  peristomial  structure  and  is  so  exten- 
sively developed  in  some  species  as  to  hide  the  prostomium 
entirely. 

3.  Identify  eight  setigerous  somites  anteriorly,  in  which 
the  capillary  setae  are  in  the  notopodium  and  the  uncini,  or 
hooked  setae,  are  in  the  neuropodium.  With  the  peristomium 
they  form  a  "thorax"  of  nine  somites.  In  the  somites  which 
follow  (the  "abdomen")  observe  that  the  uncini  and  the  capil- 
lary setae  stand  in  the  reverse  order.  How  do  you  interpret 
the  above  fact? 

4.  Find  the  ventral  shield  glands.  A  furrow  (sulcus  or 
fecal  groove)  divides  them  into  pairs  toward  the  posterior 
end  of  the  worm. 

A  drawing  is  desirable. 

HYDROIDES 

This  is  a  member  of  the  family  Serpulidae.  Study  living 
specimens  and  their  heavy  calcareous  tubes.  Notice  the 
banded  branchiae  (modified  palps)  and  the  dorsally  placed 
operculum,  a  modified  gill  filament.  Look  for  "eyes"  on  the 
gill  filaments. 

When  eggs  and  sperm  are  mature  these  animals  will  shed 
them  immediately  upon  being  removed  from  their  tubes  and 
placed  in  sea  water.    The  larvae  are  typical  trochophores. 

A  drawing  is  desirable. 

Hatschek:     Entwicklung   der  Trochophora  von   Eupomatus  uncinatus, 

Philippi.     (Serpula  uncinata.)     Arb.  Zool.  Ins.,  Wien,  6,  1886. 
Okada:     Remarks   on  the   Reversible   Asymmetry   in  the   Opercula  of 

the  Polychaete  Hydroides.  Jour.  Mar.  Biol.  Assoc.  Unit.  Kingd.,  18, 

1933. 
Shearer:    On  the  Development  and  Structure   of  the  Trochophore   of 

Hydroides  uncinatus  (Eupomatus).     Quart.  Jour.  Mic.  Sci.,  56,  1911 


HYDROIDES,    SPIRORBIS,    LUMBRICUS  109 

SPIRORBIS 

This  animal  is  also  a  member  of  the  family  Serpulidae. 
Specimens  are  very  abundant  along  the  shore,  attached  to 
Fucus. 

1.  Study  the  tube  and  notice  the  way  in  which  it  "par- 
allels" the  form  of  a  small  snail  shell. 

2.  Remove  a  live  specimen  from  the  Fucus  on  which  it 
grows  and  crack  the  tube  away  with  a  needle.  Study  the 
animal  in  a  watch  glass  with  a  low  power.  Identify  the  aills, 
the  operculum  (which  serves  as  a  "brood  pouch"),  the  setae, 
and  the  collar.    Are  any  "eyes"  on  the  gills? 

3.  Study  the  egg  strings  which  are  lodged  in  the  tube,  and 
the  young  embryos  which  are  to  be  found  in  the  brood  pouch. 

A  drawing  is  desirable. 

LUMBRICUS  (Earthworm) 

Earthworms  feed  mostly  at  night.  What  reason  is  there 
for  this  habit?  You  should  look  for  earthworms  with  a  lan- 
tern some  mild,  calm  summer  evening  when  the  ground  is 
quite  moist.  See  if  they  leave  their  burrows  entirely.  How 
much  of  the  body  is  generally  protruded?  Can  you  deter- 
mine what  the  worms  are  doing?  Are  they  disturbed  by 
walking  near  them?  Are  they  ever  disturbed  by  flashing  the 
light  suddenly  upon  them?  Of  what  service  to  them  is  the 
ability  to  distinguish  light?  Look  for  castings  near  the  bur- 
rows. During  daylight  look  for  castings  and  thus  determine 
the  relative  abundance  of  worms  in  lawns,  gardens,  etc.  (As 
the  worms  come  to  the  surface  only  when  it  is  moist,  castings 
will  be  abundant  only  at  such  times.)  Do  the  casting  in- 
dicate anything  about  the  feeding  habits? 

Place  a  living  specimen  upon  moist  filter  paper  and  ob- 
serve the  direction  and  method  of  movement.  How  can  it 
reverse  its  direction?  Gently  touch  different  parts  of  the 
body  to  see  which  are  the  most  sensitive. 

Observe  the  movement  of  the  blood  in  the  dorsal  vessel. 
In  what  direction  does  it  move?  Does  the  vessel  change  in 
shape? 


110  ANNELIDA 

Place  a  preserved  specimen  in  a  dish  with  a  little  water. 

1.  Note  the  difference  in  shape  of  the  two  ends  of  the 
body.  The  mouth  is  at  the  anterior  end,  below  the  protrud- 
ing lobe  of  the  prostomium.  The  anus  is  a  vertical  slit  at 
the  end  of  the  last  somite. 

2.  How  do  the  ventral  and  dorsal  sides  differ? 

3.  The  right  and  left  sides  are  symmetrical.  Count  the 
somites  of  the  body,  compare  with  others,  and  record  the  re- 
sult. 

4.  On  the  anterior  third  of  the  body  certain  somites  are 
swollen  and  form  the  clitellum.  What  somites  are  swollen? 
The  clitellum  is  not  present  in  young  individuals.  It  is  used 
in  making  egg  cases  and  providing  food  for  developing  em- 
bryos.   Understand  how  this  is  accomplished. 

5.  On  the  ventral  side  of  the  fifteenth  somite  are  small 
swollen  areas  where  the  vasa  deferentia  open. 

6.  Setae  project  slightly  from  the  surface  of  each  somite. 
These  light  colored  spines  are  easily  felt  with  the  fingers. 
See  if  you  can  determine  the  number  and  position  of  the  rows 
by  stroking  gently.    How  are  they  used? 

Draw  a  ventral  view  of  the  anterior  end,  including  the 
clitellum,  and  another  view  of  the  posterior  end. 

Taking  care  not  to  cut  deep,  with  fine  scissors  cut  through 
the  dorsal  wall  of  the  body  of  a  preserved  specimen,  and  ex- 
tend the  cut  the  whole  length  of  the  body.  Carefully  spread 
and  pin  the  animal  open.  In  doing  this  you  must  tear  or  cut 
the  septa,  but  be  careful  not  to  tear  or  break  the  organs  that 
perforate  them. 

Alimentary  Canal. — This  consists  of  a  straight  tube  that 
runs  the  length  of  the  body. 

1.  Immediately  behind  the  mouth  is  a  muscular,  white 
organ,  the  pharynx.  Through  how  many  somites  does  this 
extend?  It  is  connected  with  the  body  wall  by  numerous, 
radiating  muscle  fibers.  What  function  do  these  fibers  per- 
form? 

2.  Behind  the  pharynx  is  the  narrow  and  long  esophagus. 
This  runs  posteriorly  between  lobed,  light  colored  organs,  the 


LUMBRICUS  111 

seminal  vesicles,  which  will  be  studied  in  connection  with  the 
reproductive  organs.  Press  these  aside  and  notice  the  small 
calciferous  glands. 

3.  The  esophagus  leads  to  the  crop,  which  lies  just  an- 
terior to  and  in  contact  with  the  gizzard.  In  what  somites 
are  these  organs  placed?  What  is  their  shape?  Do  you 
understand  the  function  of  each? 

4.  Leaving  the  gizzard  is  the  stomach-intestine,  which  runs 
through  the  remainder  of  the  body,  giving  off  lateral  diver- 
ticula in  each  somite.    Do  you  know  its  function? 

Notice  the  relation  of  the  septa  to  the  alimentary  canal. 

Circulatory  System. — 1.  Lying  dorsal  to  the  alimentary 
canal  is  the  blood  vessel  that  could  be  seen  pulsating  in  the 
living  specimen.  In  most  cases  this  vessel  is  full  of  blood 
and  appears  brown. 

2.  Near  the  anterior  end  of  the  body  large  side  branches, 
the  aortic  arches,  are  given  off  on  either  side  and  pass  down 
around  the  esophagus.  How  many  aortic  arches  do  you  find? 
In  what  somites  are  they  placed? 

3.  Examine  with  a  lens  and  see  whether  you  find  other 
vessels  connected  with  the  dorsal  aorta.  If  you  do,  determine 
how  they  are  placed.    Do  they  appear  like  the  aortic  arches? 

Make  a  drawing  of  the  anterior  end  of  the  body,  showing 
the  points  you  have  seen. 

4.  Gently  press  the  stomach-intestine  to  one  side  and  see 
if  you  find  a  blood  vessel  beneath  it.  Do  the  aortic  arches 
join  this?  Other  connections  between  blood  vessels  are  too 
small  to  be  studied  in  dissections,  but  you  should  understand 
from  textbooks  or  lectures  what  they  are,  and  the  probable 
course  of  circulation. 

Excretory  System. — 1.  A  pair  of  nephridia  occurs  in  each 
somite,  one  nephridium  on  either  side  of  the  alimentary 
canal.  (The  first  three  or  four  somites  are  not  provided  with 
nephridia.)  Each  nephridium  is  a  coiled  tube,  appearing  to 
the  unaided  eye  as  a  fluffy  mass,  that  opens  externally  be- 
tween the  groups  of  setae,  in  the  position  already  observed, 
and  internally  by  a  small  opening  near  the  funnel.    The  inner 


112  ANNELIDA 

opening  is  not  in  the  somite  in  which  the  most  of  the  tube 
lies,  but  in  the  somite  anterior  to  it.  That  is,  the  nephridium 
that  occupies  the  space  in  somite  twenty  opens  externally  on 
somite  twenty,  but  internally  perforates  the  septum  directly 
anterior  and  opens  into  somite  nineteen. 

2.  Remove  a  nephridium  with  your  forceps  and  examine 
it  with  your  microscope.  Notice  that  it  consists  of  a  coiled 
tube  of  varying  diameter.  The  funnel  is  not  easy  to  find 
and  is  hard  to  remove.  It  may  be  found  by  removing  the 
portion  of  the  septum  through  which  the  nephridium  passes 
and  examining  it  with  a  microscope. 

Draw  the  nephridia  into  your  previous  figure. 

Cut  the  stomach-intestine  behind  the  gizzard  and  pull  it 
forward,  carefully  separating  the  tissue  from  it  as  it  is  drawn 
forward,  so  underlying  organs  will  not  be  disturbed.  In  this 
way  free  the  alimentary  canal  to  the  position  of  the  pharynx. 

You  can  now  see  the  extent  of  the  nephridia,  and  pos- 
sibly see  where  they  perforate  the  septa. 

Reproductive  System. — 1.  The  seminal  vesicles  are  large 
white  bodies,  united  in  the  median  line.  They  send  three 
lobes  on  either  side,  that  normally  overlap  the  posterior  part 
of  the  esophagus.    In  what  somites  do  the  lobes  occur? 

2.  Carefully  open  the  seminal  vesicles  near  the  median 
dorsal  line  and  examine  their  contents  microscopically. 

3.  With  a  pipette  wash  out  the  contents  and  notice  the 
two  pairs  of  convoluted  funnels,  the  inner  openings  of  the 
vasa  deferentia.  The  testes  are  hard  to  find,  as  they  are  the 
same  color  as  the  coagulated  mass  that  filled  the  seminal 
vesicles.  They  are  attached  to  the  septa  just  anterior  to  the 
funnels.  The  narrow  tubes  of  the  vasa  deferentia  may  some- 
times be  seen  leaving  the  seminal  vesicles.  They  open  ex- 
ternally on  somite  fifteen. 

4.  The  ovaries  are  a  pair  of  very  small  organs  attached 
to  the  posterior  surface  of  the  septum  that  separates  the 
twelfth  from  the  thirteenth  somite,  near  the  mid  ventral  line. 
They  may  sometimes  be  found  with  a  lens,  but  usually  are 


LUMBRICUS  113 

not  visible  otherwise.  If  possible,  remove  an  ovary  and  ex- 
amine it  with  a  microscope  to  see  its  shape,  and  to  find  which 
portion  has  the  most  mature  eggs.  The  oviducts  open  into 
the  cavity  of  the  thirteenth  somite  and  externally  through 
the  ventral  wall  of  the  fourteenth  somite,  in  line  with  the 
nephridia.    They  can  seldom  be  seen  in  dissections. 

5.  Between  the  ninth  and  tenth  and  the  tenth  and  eleventh 
somites,  on  the  ventral  side,  are  two  pairs  of  white,  rounded 
pouches,  the  seminal  receptacles,  that  open  externally  but  not 
internally.  Understand  their  function.  Make  a  drawing  of 
the  reproductive  system. 

Nervous  System. — 1.  On  the  dorsal  surface  of  the  pharynx, 
near  its  anterior  end,  are  the  two  cerebral  ganglia.  They  lie 
on  either  side  of  the  median  line  and  are  connected  by  a 
stout  commissure.    In  what  somite  do  they  lie? 

2.  The  remainder  of  the  ganglia  lie  ventral  to  the  ali- 
mentary canal.  The  first  ventral  ganglia  are  connected  with 
the  cerebral  ganglia  by  connectives  that  pass  around  the  sides 
of  the  pharynx.  Adjacent  ganglia  of  the  ventral  chain  are 
united  by  connectives.  The  ganglia  of  each  somite,  and  the 
cords  that  connect  those  of  adjacent  somites,  are  fused  so 
that  the  original  paired  condition  is  not  very  apparent.  How 
far  does  the  ventral  chain  of  ganglia  extend?  Where  do 
nerves  leave  it? 

Draw  the  nervous  system  into  the  figure  that  shows  the 
reproductive  system. 

Notice  the  sacs  that  inclose  the  setae  and  indicate  them 
in  the  above  figure. 

Examine  prepared  serial  microscopic  sections.1 

1  Small  worms  should  be  kept  in  a  dish  and  fed  on  clean  moistened 
filter  paper,  which  they  will  eat  readily,  until  the  alimentary  canal  is 
free  from  grit,  before  they  are  preserved  for  sectioning.  It  is  well  to 
narcotize  them  by  placing  them  in  a  small  quantity  of  water  and  add- 
ing a  little  alcohol  from  time  to  time  (never  enough  to  make  the  worms 
squirm  violently)  until  they  cease  to  move.  They  may  then  be  killed 
with  sublimate  acetic  or  other  killing  agent  and  treated  in  the  usual 
manner. 

8 


114  ANNELIDA 

1.  The  cuticle  will  probably  be  absent  in  most  sections, 
in  which  case  the  outer  covering  will  be  the  cellular  hypo- 
dermis  or  skin.  How  many  cells  thick  is  this  layer?  Look 
for  the  gland  cells  that  keep  the  living  worm  moist.  Do  you 
know  how  the  cuticle  is  formed? 

2.  Beneath  the  hypodermis  is  the  circular  muscle  layer, 
which  is  followed  by  the  longitudinal  muscle  layer.  The 
fibers  of  the  latter  are  arranged  in  conspicuous  bundles. 
Lining  the  body  wall  is  the  thin  peritoneal  layer.  Do  you 
understand  the  function  of  each  of  these  layers?  How  is  the 
body  elongated? 

3.  Find  the  setae  and  determine  where  they  are  placed, 
how  many  are  in  each  group,  how  many  groups  there  are, 
how  they  pierce  the  body  wall,  and  what  muscles  are  at- 
tached to  them.    Why  are  setae  not  in  every  section? 

4.  The  alimentary  canal  consists  of  a  lining  epithelium, 
followed  by  connective  tissue  and  muscle,  and,  on  its  outer 
wall,  peritoneal  cells,  which  in  the  region  of  the  stomach-in- 
testine are  large,  very  numerous,  and  are  known  as  the 
chlorogogue  cells. 

5.  Lying  in  the  midventral  line,  beneath  the  alimentary 
canal  and  close  to  the  body  wall,  is  the  ventral  nerve  cord. 
Examine  its  structure.    See  if  any  of  the  sections  show  nerves 

leaving  it. 

6.  Dorsal  to  the  alimentary  canal  is  the  dorsal  blood  ves- 
sel, on  its  ventral  side  is  the  ventral  blood  vessel,  and  ventral 
to  the  nerve  cord  the  subneural  vessel. 

7.  Find  sections  of  the  nephridia.  Where  are  they  placed? 
How  do  the  sections  appear?    Why? 

Other  organs  will  appear  in  most  of  the  sections.  See  if 
you  can  identify  them. 

Draw  an  enlarged  cross  section. 

Darwin:    The   Formation   of  Vegetable   Mold   through   the   Action   of 

Worms.     Appleton  and  Co.,  1888. 
Harrington:    The  Calciferous  Glands  of  the  Earthworm,  with  Appendix 

on  the  Circulation.     Jour.  Morph.,  15,  1899. 


LUMBRICUS,    MACROBDELLA  115 

Parker  and  Arkin :   The  Directive  Influence  of  Light  on  the  Earthworm, 

Allolobophora  fcetida.     Am.  Jour.  Physiol.,  4,  1901. 
Sedgewick  and  Wilson:    General  Biology. 
Wilson:    The  Embryology  of  the  Earthworm.     Jour.  Morph.,  3,  1889. 

%  MACROBDELLA  (Leech) 

If  you  have  living  specimens  notice  their  methods  of  loco- 
motion both  in  crawling  around  the  dish  and  in  swimming. 
A  considerable  volume  of  water  is  usually  necessary  to  get 
the  animals  to  swim. 

Specimens  may  be  killed  with  chloroform,  narcotizing  ma- 
terials, or  killing  agents,  such  as  weak  chromic  acid. 

1.  Observe  the  shape  of  the  body.  Which  is  the  anterior 
end? 

2.  Do  the  dorsal  and  ventral  surfaces  differ  in  shape  and 
color? 

3.  Note  the  rings  which  encircle  the  body.  Determine 
their  number.  There  is  good  evidence  that  these  do  not  rep- 
resent somites.  The  somites  are  fewer  in  number  and  each 
is  composed  of  from  one  to  five  of  these  rings. 

On  the  dorsal  surface: 

1.  Near  the  anterior  end  is  a  series  of  ten  small  black 
spots  arranged  in  the  form  of  a  horseshoe  with  the  arched 
end  forward.  These  are  the  eyes.  They  are  arranged  in 
pairs  on  the  first,  second,  third,  fifth,  and  eighth  rings.  These 
are  believed  to  be  on  the  first  five  somites.  The  first  and 
second  somites  comprise  a  single  ring  each;  the  third  in- 
cludes the  third  and  fourth  rings;  the  fourth — the  fifth,  sixth, 
and  seventh  rings;  the  fifth — the  eighth,  ninth,  and  tenth 
rings. 

2.  Near  the  lateral  edges  notice  the  black  pigment  spots. 
The  larger  spots  are  situated  mostly  on  a  single  ring,  but 
may  be  extended  on  to  others.  Smaller  pigment  spots  may 
occur  on  other  rings  along  the  same  line.  There  is  evidence 
that  these  larger  spots  mark  the  anterior  rings  of  each  somite 
wherever  they  occur.  How  many  rings  are  commonly  in- 
cluded in  a  somite? 


116  ANNELIDA 

3.  On  the  midline  between  these  pigment  spots  are  white 

spots. 

4.  If  the  specimen  is  favorable  you  may  find  with  a  lens 
a  series  of  segmental  sense  organs  on  the  first  ring  of  each 
somite.  They  are  of  unknown  function,  the  eyes  are  supposed 
to  be  developed  from  certain  of  these  organs,  and  they  are 
landmarks  in  determining  the  morphological  boundaries   of 

somites. 

5.  On  the  median  line  in  the  groove  that  separates  the 
most  posterior  ring  from  the  sucker  find  the  anus. 

Make  a  drawing  of  the  dorsal  surface. 
On  the  ventral  surface: 

1.  The  mouth,  at  the  anterior  end  of  the  body,  is  bounded 
by  the  proboscis  dorsally  and  anteriorly  and  by  the  fourth 
ring  ventrally.  Determine  its  shape.  The  mouth  with  the 
region  around  it  forms  the  anterior  sucker. 

2.  The  male  reproductive  aperture  is  on  the  median  ven- 
tral portion  of  the  thirtieth  ring.  This  is  surrounded  by  a 
thickening. 

3.  The  female  reproductive  aperture  is  on  the  median  line 
at  the  posterior  margin  of  the  thirty-fifth  ring.  This  is  not 
marked  by  a  distinct  thickening. 

4.  Find  four  apertures  with  thickened  margins  arranged 
in  the  form  of  a  square  between  the  thirty-ninth  and  fortieth 
and  the  fortieth  and  forty-first  rings.  These  are  the  aper- 
tures of  the  mucous  glands. 

5.  Find  the  external  apertures  of  the  nephridia  about  half 
way  between  the  median  line  and  the  margins,  on  the  pos- 
terior edge  of  the  last  ring  of  a  somite.  The  spots  are  light 
colored  and  elliptical.  These  are  important  landmarks  in 
determining  the  boundaries  of  somites.  Some  of  the  anterior 
and  posterior  somites  do  not  bear  them. 

6.  Observe  the  size,  shape,  and  structure  of  the  posterior 
sucker. 


MACROBDELLA  117 

Preserved  specimens  if  very  hard  should  be  placed  in 
water  some  time  before  dissection.  Cut  through  the  body 
wall  along  the  mid-dorsal  line,  being  careful  not  to  cut  under- 
lying organs.  Lift  up  the  flap  of  integument  and  cut  the 
connective  tissue  loose  so  it  may  be  turned  and  pinned  back 
under  water.  Work  forward  and  backward  from  the  middle 
of  the  back. 

1.  The  digestive  tract  consists  of  a  buccal  pouch,  pharynx, 
stomach,  and  intestine. 

2.  The  pharynx  is  thick  walled,  elongated,  and  bound  to 
the  body  wall  by  radiating  muscle  fibers.  What  is  their  func- 
tion? The  pharynx  is  muscular  and  is  provided  with  bands 
of  longitudinal  and  with  circular  muscles.  What  function  is 
performed  by  these  fibers? 

3.  The  stomach  joins  the  pharynx,  is  large,  and  has  di- 
verticula that  nearly  fills  the  body  cavity.  It  occupies  a 
considerable  portion  of  the  length  of  the  body.  How  many 
pouches  has  it?  Do  the  pouches  bear  any  relation  to  the 
somites?  The  posterior  end  of  the  stomach  narrows  and  pro- 
jects into  the  intestine. 

4.  The  intestine  is  enlarged  a  little  at  its  anterior  end  and 
tapers  posteriorly  to  a  slight  dilatation,  sometimes  called  the 
colon.    From  this  a  short  rectum  runs  to  the  anus. 

Make  a  sketch  of  the  digestive  tract. 

5.  Open  the  digestive  tract,  wash  it  out,  and  examine  with 
a  lens.  Especially  study  the  pharynx  and  see  how  the  suck- 
ing action  is  produced,  and  how  the  blood  is  forced  into  the 
stomach.    The  cavity  of  the  mouth  will  be  studied  later. 

Cut  the  digestive  tract  at  the  rectum  and  at  about  the 
middle  of  the  pharynx  and  carefully  dissect  it  loose. 

Beneath  it  notice: 

1.  The  nerve  cord.  Do  the  ganglia  have  any  relation  to 
somites?  Find  the  lateral  nerves  leaving  them.  Trace  the 
connectives  between  them.  This  will  receive  more  attention 
later. 


118  ANNELIDA 

2.  The  ventral  blood  vessel  and  the  lateral  branches. 

3.  The  nephridia,  of  which  there  are  eighteen  pairs. 

4.  The  male  reproductive  organs.  On  the  midventral  line 
ventral  to  the  nerve  cord,  and  opposite  the  external  opening 
already  observed,  is  the  globular  muscular  penis.  Just  an- 
terior and  laterally  are  a  pair  of  white  seminal  vesicles.  A 
short  broad  duct  leads  from  each  vesicle  to  the  penis  and  a 
long  narrow  duct  leads  posteriorly  to  connect  with  the  nine 
testes  on  the  same  side.  The  anterior  pair  of  testes  are  four 
somites  behind  the  penis  and  the  eight  others  are  in  the  suc- 
ceeding somites.  The  testes  are  rounded  white  organs  near 
the  nerve  cord. 

5.  The  female  reproductive  organs  which  lie  behind  the 
penis.  The  vagina  is  a  muscular  sac  on  the  median  line  op- 
posite the  opening  already  described.  From  the  anterior 
dorsal  side  the  oviducts  run  to  the  two  small  white  ovaries, 
which  are  near  the  vagina,  but  a  little  anterior  and  lateral 

to  it. 

6.  Four  mucous  glands,  behind  the  vagina  and  opposite 
the  openings  on  the  ventral  side. 

Draw. 

Nervous  System. — The  location  of  the  ventral  cord  has 
already  been  noticed. 

(a)  How  many  ganglia? 

(b)  Are  the  ganglia  of  equal  size?  Do  they  all  give  off 
the  same  number  of  lateral  nerves? 

(c)  Find  the  supra- esophageal  ganglia,  above  the  pharynx. 

(d)  Observe  the  connectives  that  join  the  supra-esopha- 
geal  ganglia  to  the  first  pair  of  the  ventral  chain,  the  infra- 
esophageal  ganglia. 

(e)  Find  the  nerves  that  run  from  the  supra-esophageal 
ganglia  to  the  eyes. 

(/)  There  are  three  stomogastric  ganglia,  one  on  each 
side  of  the  muscular  lobes  of  the  buccal  pouch  and  one  on 


MACROBDELLA,    PHASCOLOSOMA  119 

the  median  line.  These  are  joined  to  the  supra-esophageal 
ganglia. 

Draw  the  nervous  system. 

Open  the  buccal  cavity  by  cutting  along  one  side  and 
notice  the  three  large  buccal  muscles,  one  dorsal  and  two 
lateral.  These  bear  many  minute  denticles  that  may  be  seen, 
in  the  right  position,  with  a  compound  microscope.  It  is  by 
means  of  these  that  the  leech  makes  its  wound. 

GEPHYREA 
PHASCOLOSOMA 

This  form  is  commonly  found  buried  in  sand  between 
tide  marks.  Specimens  sometimes  occur  on  the  same  flats 
with  Nereis,  but  they  are  generally  more  abundant  where  the 
mud  is  of  a  slightly  different,  more  sticky  character. 

1.  Handle  a  living  specimen  and  see  how  turgid  it  is.  If 
you  touch  a  specimen  that  has  been  allowed  to  expand  in  a 
dish  of  sea  water  you  will  find  it  is  rather  soft,  but  becomes 
turgid  upon  being  touched.    How  is  this  accomplished? 

2.  Examine  a  living  animal  in  a  dish  of  sea  water.  The 
anterior  portion  of  the  body,  the  introvert,  is  drawn  in,  but 
may  occasionally  be  extended,  when  it  will  be  seen  to  bear 
at  the  anterior  extremity  a  crescentic  crown  of  tentacles, 
which  partly  surrounds  the  mouth. 

3.  Compare  with  a  preserved  specimen  which  has  been 
killed  with  the  introvert  extended. 

Make  drawings  showing  the  animal  with  the  introvert 
protruded  and  with  the  introvert  concealed. 

4.  The  anus  is  located  on  a  dorsal  papilla,  anterior  to  the 
middle  of  the  body.  Near  the  anus  a  pair  of  lateral  papillae 
mark  the  position  of  the  nephridiopores.  The  coiled  intes- 
tine and  brown  nephridial  tubes  can  probably  be  seen  through 
the  body  wall.  Note  carefully  the  character  of  the  integu- 
ment. Is  there  any  indication  of  spines,  appendages,  or  eye 
spots? 

For  dissection  use  both  fresh  and  preserved  specimens. 


120  ANNELIDA 

With  scissors  open  the  worm  from  end  to  end  near  the 
mid-dorsal  line,  and  pin  the  body  wall  out  flat. 

5.  In  opening  the  fresh  worm,  note  the  pinkish  coelomic 
fluid  which  fills  the  coelom.  Examine  a  drop  under  the  micro- 
scope.   What  functions  has  this  fluid  to  perform? 

Alimentary  Canal. — Trace  the  alimentary  canal  (stomach- 
intestine)  from  mouth  to  anus.  Do  any  digestive  glands  open 
into  it  at  any  point?  Note  the  mesenteric  thread  which  runs 
through  the  axis  of  the  intestine  spiral.  Where  is  it  at- 
tached?   Does  it  seem  to  be  contractile  in  the  fresh  worm? 

Muscular  System. — Note  the  silvery  white  longitudinal 
muscles  composing  the  inner  layer  of  the  body  wall.  Are 
they  arranged  in  distinct  bands  or  in  a  continuous  sheet? 
Remove  some  of  these  muscles  carefully  to  expose  the  layer 
of  circular  muscles.  How  many  retractor  muscles  of  the  in- 
trovert are  there?  How  is  the  mechanism  of  protrusion  of 
the  introvert  to  be  explained? 

Circulatory  System. — This  system  is  very  difficult  to  ob- 
serve. Dorsal  and  ventral  blood  sinuses  are  present,  and 
communicate  anteriorly  by  a  circular  sinus.  A  blood  sinus, 
purplish  red  in  living  specimens,  occurs,  as  an  irregular  tube, 
along  the  anterior  portion  of  the  esophagus  and  intestine. 

Excretory  System. — Find  a  pair  of  brown  nephridia,  an 
inch  or  more  in  length.  Cut  off  a  nephridium  (from  the 
fresh  worm)  as  close  as  possible  to  the  body  wall,  and  ex- 
amine it  under  a  microscope.  Near  the  cut  (the  attached) 
end  find  the  coelomic  opening  or  nephrostome.    Is  it  ciliated? 

Reproductive  System. — The  sexes  are  separate.  Oogonia 
and  spermatogonia  are  detached  from  the  coelomic  epith- 
elium, at  the  points  where  the  ventral  retractor  muscles  are 
attached  to  the  body  wall.  These  cells  become  mature  while 
floating  in  the  coelomic  fluid.  They  pass  out  through  the 
nephridia,  which  function  as  gonoducts. 

Nervous  System. — Does  the  ventral  nerve  cord  seem  to  be 
double?  Is  it  ganglionated?  Does  it  give  off  lateral  nerve 
branches?     Trace  the   circumesophageal   connectives  to   the 


PHASCOLOSOMA  121 

supra- esophageal  ganglion.     The  ganglion  is  small  and  situ- 
ated behind  the  crown  of  tentacles,  to  which  sensory  nerves 
extend.    Does  any  system  of  organs  show  segmentation? 
Make  a  drawing  to  show  the  internal  anatomy. 

Adolph:     Some    Physiological    Distinctions    between    Fresh-water    and 

Marine  Organisms.    Biol.  Bull.,  48,  1925. 
Gerould:    The  Development  of  Phascolosoma.     Zool.  Jahrb.,  23,  1906. 
Wilson,  C.  B.:    Our  North  American  Echiurids.     Biol.  Bull.,  1,   1900. 


MOLLUSCA 

Unsegmented.     Usually  provided  with  a  calcareous  pro- 
tecting shell  and  a  ventral  foot. 

Class  1.  Pelecypoda.      (Lamellibranchiata.) 

Bivalve  shell.  Gills  adapted  for  gathering 
food  as  well  as  for  respiration.  Foot  usually 
adapted  for  burrowing.    No  hard  mouth  parts. 

Order  1.  Protobranchia. 

Gills  composed  of  a  series  of  transverse  plates. 
Foot  apparently  split  at  the  end.  Two  adduc- 
tor muscles,  posterior  frequently  the  smaller. 
(Nucula,  Yoldia.) 

Order  2.  Filibranchia. 

Gills  lamelliform.  Filaments  united  by  modi- 
fied cilia.  Anterior  adductor  muscle,  fre- 
quently greatly  reduced.  (Mytilus,  Modio- 
lus.) 

Order  3.  Pseudolamellibranchia. 

Gills  lamelliform.  Interfilamentar  junctions 
usually  not  very  extensive,  may  be  either  cili- 
ary or  vascular.  Only  one  adductor  muscle. 
(Pecten,  Ostrea.) 

Order  4.  Eulamellibranchia. 

Gills  lamelliform.  Interfilamentar  junctions 
extensive  and  vascular.  Adductor  muscles  of 
nearly  equal  size.     (Venus,  Unio,  Mya.) 

Order  5.  Septibranchia. 

Gills  reduced  to  a  horizontal  partition.     Two 
adductor  muscles.     Deep  sea  forms.     (Silenia, 
Cuspidaria.) 
Class  2.  Amphineura. 

Bilaterally  symmetrical,  elongated.  Nervous 
system  not  concentrated.  Radula  sometimes 
present.  Shell,  when  present,  composed  of 
eight  transverse  pieces. 

Order  1.  Placophora. 

Dorsal    shell,    composed    of    eight    transverse 
pieces.      Foot    broad.      Gills    simple,    lateral. 
(Chiton,  Chaetopleura,  Trachydermon.) 
122 


MOLLUSCA  123 

Order  2.  Aplacophora. 

Body  elongated,  covered  by  a  mantle.     Adult 
without  shell  but  with  spicules.    No  true  foot. 
Gills  posterior.     (Neomenia,  Dondersia.) 
Class  3.  Gastropoda. 

Body    unsymmetrical,    usually    covered    by    a 
spiral     shell.       Foot    usually     flattened     and 
adapted  for  creeping.    Radula  usually  present. 
Subclass  1.  Streptoneura. 

Nervous  system  twisted  into  the  form  of  a 
figure  8.     Sexes  separate. 

Order  1.  Aspidobranchia. 

Nervous  system  not  concentrated.  Gills  usu- 
ally present  and  paired.  Auricles  paired. 
(Acmaea,  Patella,  Haliotus.) 

Order  2.  Pectinibranchia. 

Nervous      system      somewhat      concentrated. 
Single  gill.    Single  auricle.     (Buccinum,  Busy- 
con,  Crepidula.) 
Subclass  2.  Euthyneura. 

Nervous  system  not  twisted  into  the  form  of  a 
figure  8.     Hermaphroditic. 

Order  1.  Opisthobranchia. 

Aquatic  respiration.  Shell  when  present 
rather  delicate.     (Bulla,  Aeolis.) 

Order  2.  Pulmonata. 

Air  breathers.    Live  on  land  or  in  fresh  water. 
Aperture  to  mantle   cavity  narrow   and   con- 
tractile.    (Limax,  Limnaea,  Helix.) 
Class  4.  Scaphopoda. 

Bilaterally  symmetrical.     Shell  tubular,  elon- 
gated dorsoventrally  and  open  at  both  ends. 
Foot  conical.     (Dentalium.) 
Class  5.  Cephalopoda. 

Bilaterally  symmetrical.     Shell  chambered  or 
reduced    and    internal.      Distinct    head    with 
arms  bearing  suckers. 
Subclass  1.  Dibranchiata. 

Arms  forming  a  circlet  around  the  mouth. 
Funnel  a  complete  tube.  Shell  usually  inter- 
nal.   Two  gills. 

Order  1.  Decapoda. 

Ten  arms,  two  of  which  are  elongated,  suckers 
on  stalks.     (Loligo,  Sepia,  Spirula.) 


124  MOLLUSCA 

Order  2.  Octopoda. 

Eight  arms,  suckers  sessile.     (Octopus,  Argo- 
nauta.) 
Subclass  2.  Tetrabranchiata. 

Tentacles     numerous.       External     chambered 
shell.    Funnel  open  along  one  side.     Only  one 
living  genus.     Four  gills.      (Nautilus.) 
Brooks:    The  Origin  of  the   Oldest  Fossils  and  the  Discovery  of  the 

Bottom  of  the  Ocean.    Smithsonian  Rept.,  1894. 
Coe:    Sexual  Rhythm  in  Teredo.    Science,  80,  1934. 
Kellogg:   Contribution  to  our  Knowledge  of  the  Morphology  of  Lamelli- 
branchiate  Mollusks.    Bull.  U.  S.  Fish  Com.,  1890. 

:    Shell-fish  Industries.    Henry  Holt  and  Co.,  1910. 

:     Ciliary    Mechanisms   of    Lamellibranches,   with    Description    of 

Anatomy.    Jour.  Morph.,  26,  1915. 
Pelseneer:    Contribution  a  L 'Etude  des  Lamellibranches.    Arch.  d.  Biol., 
11,  1891. 

:     Recherches    Morphologiques    et    Phylogenetiques    sur    les    Mol- 

lusques  Archaiques.    Acad.  roy.  d.  Sci.  d.  lettres  et  d.  beaux-arts  d. 

Belgique,  1899. 

Etude  sur  des  Gastropodes  Pulmones.    Mem.  Acad.  roy.  d.  Sci.  d. 


lettres  et  d.  beaux-arts  de  Belgique,  1901. 
Ridewood:     On  the   Structure  of   the   Gills   of   Lamellibranchs.     Phil. 

Trans.  Roy.  Soc,  London,  B,  195,  1903. 
Stenta:    Zur  Kenntnis  der  Stromungen  im  Mantelraume  der  Lamelli- 

branchiaten.     Arb.  Zool.  Inst.  Univ.  Wien,  14,  1902. 

PELECYPODA 

VENUS  MERCENARIA  (Quahog)1 

Animals  of  this  species  wander  around  over  muddy  bot- 
toms in  rather  shallow  water,  keeping  the  siphon  end,  at 
least,  above  the  surface  of  the  mud.  If  possible,  you  should 
find  specimens  in  their  native  places  and  watch  their  move- 
ments. Specimens  placed  in  water  and  left  undisturbed  for 
some  hours  are  likely  to  protrude  the  siphons,  and  the  foot 
may  be  protruded  in  some  cases.2  Allow  powdered  carmine 
to  settle  slowly  past  the  openings  of  the  siphons  and  deter- 
mine the  direction  of  the  current  of  water  for  each.     Touch 

1  Points  in  which  the  fresh-water  mussel  differ  have  been  noted,  so 
the  directions  may  be  used  for  that  form. 

2  Other  species  of  lamellibranchs  are  more  satisfactory  than  Venus 
for  studying  movements,  as  they  expand  quickly  after  being  disturbed. 
Among  the  common  ones  that  may  be  mentioned  are  Ensis,  Cumingia, 
Yoldia,  and  Mytilus. 


VENUS  125 

portions  of  the  animal  and  find  what  parts  are  most  sensi- 
tive. 

Shell. — Note  its  general  shape,  and  that  it  is  composed 
of  two  symmetrical  parts,  the  valves.    For  each  valve  notice: 

1.  The  outline. 

2.  A  swelling,  the  umbo,  ending  in  a  point,  the  beak,  from 
which  growth  has  proceeded. 

3.  The  lines  of  growth.  Were  the  valve  cut  off  along  one 
of  these  lines,  the  shape  would  not  be  changed.  Why  are 
the  lines  arranged  in  this  manner?    How  were  they  formed? 

The  two  valves  are  joined  by  the  ligament.  The  margin 
bearing  the  ligament  is  dorsal,  and  that  toward  which  the 
beaks  point  is  anterior.     Which  valve  is  right  and  which  is 

left? 

Draw  a  valve,  showing  the  points  observed. 

Pry  the  two  valves  apart  and  insert  a  knife  blade  between 
the  mantle  and  one  valve  of  the  shell.  Notice  that  the  lobes 
of  the  mantle  are  loosely  attached  to  the  shell  along  their 
margins,  and  more  firmly  attached  a  half  inch  or  more  from 
the  margins. 

Separate  the  mantle  from  one  valve,  and  cut  the  adduc- 
tors where  they  are  attached  to  this  valve.  Why  do  the 
valves  gape  now?  Press  them  together,  and  notice  that  they 
stay  closed  only  while  held.  Remove  a  valve  and  study  its 
interior. 

1.  Find  the  large  scars  where  the  anterior  and  posterior 
adductor  muscles  were  attached. 

2.  Find  smaller  scars  where  the  anterior  and  posterior 
foot  muscles  were  attached.  The  anterior  scar  is  dorsal  and 
a  little  posterior  to  the  corresponding  adductor  muscle  scar. 
(Not  the  position  for  Unio.)  The  posterior  scar  connects 
with  the  dorsal  portion  of  the  corresponding  adductor  muscle 

scar. 

3.  The  ventral  borders  of  the  adductor  muscle  scars  are 
connected  by  a  distinct  line,  the  pallial  line.  What  forms  it? 
The  posterior  end  of  this  line  is  indented  to  form  the  pallial 


126  MOLLUSCA 

sinus.     (Not  true  for  Unio.)     What  is  the  meaning  of  this 
sinus? 

4.  Along  the  dorsal  margin  of  the  valve  notice  promi- 
nences, the  teeth.  There  are  two  kinds  of  teeth.  The  an- 
terior, cardinal,  consist  of  short  elevations.  The  posterior, 
lateral,  are  not  very  prominent,  but  are  comparatively  long 
and  extend  along  the  dorsal  margin.  Notice  that  the  teeth 
on  the  two  valves  interlock.    What  is  their  function? 

Draw  a  valve  as  seen  from  the  inside. 

5.  By  examining  the  inside  of  a  shell  of  Unio  or  Mytilus 
near  its  margin,  the  typical  three  layers  of  which  it  is  com- 
posed can  be  seen.  How  is  it  possible  for  all  three  layers  to 
be  secreted  by  the  mantle,  which  lines  the  inside  of  the  shell? 
Can  you  find  any  reason  for  more  than  one  layer? 

Mantle. — This  consists  of  a  dorsal  covering  and  two  lateral 
lobes  (one  of  which  is  applied  to  the  inner  surface  of  each 
valve  of  the  shell). 

1.  The  free  border  of  each  lobe  is  thickened,  and  contains 
muscles  that  were  attached  to  the  shell  along  the  pallial  line. 
What  function  do  these  muscles  perform? 

2.  The  posterior  portions  of  the  lobes  of  the  mantle  are 
thickened  and  united  to  each  other  so  as  to  form  two  tubes 
(in  Unio  the  ventral  tube  is  formed  by  contact  only),  the 
siphons,  through  which  water  passes  into  and  out  of  the  shell. 

3.  See  how  the  muscles  of  the  siphons  are  arranged  and 
attached.  Does  the  attachment  bear  any  relation  to  the  pal- 
lia! sinus  in  Venus? 

Visceral  Mass  and  Foot. — These  portions  form  the  large 
median  mass.  The  viscera  are  contained  in  the  dorsal  por- 
tion. 

1.  The  ventral  portion  is  hard  and  muscular,  and  forms 
the  foot. 

2.  Besides  the  crossing  muscle  fibers  of  which  the  foot  is 
largely  composed,  it  is  supplied  with  two  pairs  of  muscles 
that  are  attached  to  the  shell.  The  cut  ends  of  these  muscles, 
the  anterior  and  the  posterior  foot  muscles,  may  be  seen  pro- 


VENUS  127 

truding  through  the  lobe  of  the  mantle.1  They  correspond  in 
position  to  the  scars  on  the  shell. 

Do  you  understand  by  what  means  the  foot  is  protruded? 

Gills. — These  consist  of  two  pairs  of  thin,  striated,  some- 
what brownish  organs,  a  pair  lying  on  each  side  of  the  vis- 
ceral mass,  between  it  and  the  lobes  of  the  mantle. 

1.  Each  gill  extends  from  the  wall  that  separates  the  two 
siphons,  anteriorly  and  dorsally  to  a  point  nearly  opposite  the 
beaks  of  the  shell,  and  is  attached  by  its  dorsal  margin  only. 

2.  Each  outer  gill  is  attached  along  its  dorsal  border  to 
the  corresponding  mantle  lobe  on  the  outer  side.  The  inner 
gills,  besides  being  attached  to  the  dorsal  margins  of  the 
outer  gills,  are  on  their  inner  sides  attached  to  each  other  and 
to  the  visceral  mass.  (For  some  distance  the  inner  side  of 
the  inner  gill  lies  against  the  visceral  mass,  but  is  not  at- 
tached to  it.) 

By  this  arrangement  the  space  between  the  lobes  of  the 
mantle,  which  is  known  as  the  mantle  chamber,  is  divided 
into  a  ventral  and  a  dorsal  portion.  The  ventral  portion  is 
much  the  larger,  communicates  with  the  ventral  siphon,  and 
because  the  gills  hang  into  it,  it  is  known  as  the  branchial 
chamber.  The  dorsal  chamber  is  known  as  the  cloacal  cham- 
ber. The  siphons  are  frequently  referred  to  by  names  cor- 
responding to  the  chambers  with  which  they  communicate. 
The  minute  structure  of  the  gills  will  be  studied  later. 

3.  Place  a  little  powdered  carmine  on  the  gill  of  a  speci- 
men that  is  submerged  in  sea  water  and  see  what  becomes 
of  it. 

Labial  Palps. — These  consist  of  a  pair  of  rather  small 
triangular  flaps  on  each  side  of  the  visceral  mass. 

1.  The  two  outer  palps  are  united  above  the  mouth,  which 

is  situated  just  posterior  to  the  dorsal  border  of  the  anterior 

1The  anterior  foot  muscles  are  sometimes  called  protractors,  and 
the  posterior  foot  muscles  retractors.  Both  are  actually  used  to  retract 
the  foot.  The  greatly  retracted  foot  may  be  pulled  slightly  forward  by 
the  anterior  muscles,  but  the  mechanism  of  protruding  the  foot  is  very 
different. 


128  MOLLUSC  A 

adductor  muscle,  and  form  a  small  fold  that  corresponds  in 
position  to  an  upper  lip. 

2.  The  two  inner  palps  likewise  unite  to  form  a  fold  cor- 
responding in  position  to  an  under  lip. 

Make  a  drawing  showing  the  arrangement  of  the  soft 
parts. 

Structure  of  a  Gill. — Cut  off  a  piece  of  the  edge  of  a  gill, 
put  it  on  a  slide  with  a  drop  of  sea  water,  and  examine  with 
a  low  power  of  the  microscope. 

1.  Notice  the  cilia  on  the  edge  and  surface  of  the  gill. 

2.  The  surface  is  marked  by  a  series  of  parallel  ridges, 
the  filaments,  with  grooves  between  them.1 

The  filaments  are  joined  together  laterally  by  series  of 
bridges  (you  will  see  them  later),  the  inter filament ar  junc- 
tions, with  the  pores,  inhalant  ostia,  between  them.  Each 
side  of  the  gill  is  thus  composed  of  a  single  layer  of  united 
parallel  filaments,  which  together  form  what  is  known  as  a 
lamella.  Each  gill  is  composed  of  two  such  lamellae,  one  on 
each  side.  These  lamellae  are  united  at  intervals  by  bridges 
that  run  the  whole  width  of  the  gill  (dorsal  to  ventral) ,  par- 
allel to  the  filaments,  and  at  right  angles  to  the  interfilamen- 
tar  junctions.  These  are  called  the  interlamellar  junctions. 
By  means  of  the  interlamellar  junctions,  the  space  between 
the  two  lamellae  is  divided  into  a  series  of  water  tubes.  The 
openings  of  these  tubes  into  the  cloacal  chamber  may  easily 
be  seen  after  the  cloacal  chamber  has  been  cut  open. 

3.  Separate  a  small  piece  of  one  lamella  from  the  other. 
This  can  be  done  most  readily  by  catching  the  free  dorsal 
border  of  the  inner  lamella  of  an  inner  gill  with  the  forceps, 
and  either  tearing  off  a  piece  or  freeing  it  by  cutting  with 
scissors  while  it  is  being  pulled  with  the  forceps.  Mount  this 
piece,  with  the  outer  surface  up,  under  a  cover  glass  in  a  drop 
of  sea  water  and  observe,  with  a  lower  power,  the  following: 

1  The  general  surface  features  are  especially  easily  seen  in  Pecten, 
where  the  interfilamentar  junctions  are  small  and  well  marked,  and  the 
inhalant  ostia  are  correspondingly  large  and  distinct. 


VENUS  129 

(a)  Filaments.    Run  the  width  of  the  gill. 

(b)  Interfilamentar  junctions.  Form  bridges  connecting 
the  filaments. 

(c)  Inhalant  ostia.  The  openings  bounded  by  filaments 
and  interfilamentar  junctions. 

(d)  The  position  of  the  torn  interlamellar  junctions,  ap- 
pearing as  indefinite  dark  stripes  running  in  the  same  direc- 
tion as  the  filaments. 

With  a  high  power  observe: 

(a)  The  chitinous  rods  which  lie  inside  of  the  filaments 
and  stiffen  them. 

{b)  The  cilia  on  the  sides  of  the  filaments.  These  are  of 
two  kinds:  (1)  surface  cilia  that  form  currents  of  water 
along  the  filaments.  These  will  be  seen  waving  back  and 
forth,  or  if  still  moving  rapidly,  apparently  moving  along  the 
sides  of  the  filaments.  (2)  Deeper  cilia  that  are  down  be- 
tween the  filaments  and  can  be  seen  by  changing  the  focus. 
These  move  at  right  angles  to  the  others,  and  apparently 
become  longer  and  shorter.    Explain. 

Draw  a  surface  view  of  a  piece  of  a  lamella. 

Examine  a  piece  of  the  gill  of  Mytilus  for  the  above  struc- 
tures. In  this  form  the  interfilamentar  junctions  are  small 
and  composed  of  modified  cilia  only,  and  the  inhalant  ostia 
are  correspondingly  large.  By  pressing  the  gill  the  inter- 
filamentar junctions  can  be  pulled  apart. 

Study  prepared  sections  of  the  gill  of  Venus  and  notice: 

1.  Lamellae. 

2.  Interlamellar  junctions. 

3.  Water  tubes. 

4.  Filaments. 

5.  Interfilamentar  junctions. 

6.  Cilia. 

7.  Inhalant  ostia. 

8.  Blood  spaces. 

9.  Chitinous  rods. 
Draw. 

9 


130  MOLLUSCA 

Understand  the  direction  taken  by  water  in  passing  from 
the  branchial  to  the  cloacal  siphon.  What  makes  the  water 
move? 

Labial  Palps. — The  positions  of  these  organs  have  already 
been  noted. 

1.  Examine  a  piece  of  the  palp  with  a  microscope,  and 
notice  that  the  side  turned  toward  the  adjacent  palp  is 
thrown  into  ridges  and  grooves,  and  is  densely  ciliated. 

2.  The  space  between  each  outer  and  inner  palp  is  con- 
tinuous with  the  "corners"  of  the  mouth.  The  free  margins 
come  close  to  the  borders  of  the  gills  and  normally  inclose 
them. 

Understand  how  food  is  gathered  and  carried  to  the 
mouth. 

Circulatory  System. — The  pericardium,  in  which  the  heart 
lies,  is  a  somewhat  triangular  space  that  appears  clear, 
through  the  mantle.  It  lies  just  anterior  to  the  posterior  ad- 
ductor muscle.  Open  the  pericardium,  and  notice  the  beating 
of  the  heart.     The  heart  consists  of  three  parts: 

1.  A  central  portion,  the  ventricle,  which  surrounds  the 
intestine  and  gives  rise  to  a  blood  vessel  at  each  end. 

2.  Two  triangular  portions,  the  auricles,  which  receive 
blood  from  the  gills  and  open  into  the  sides  of  the  ventricle. 

Notice  the  sequence  and  power  of  the  contractions. 

Just  posterior  to  the  pericardium  is  an  enlarged  portion 
of  the  alimentary  canal.  This  has  no  relation  to  the  heart, 
for  which  it  is  sometimes  mistaken. 

Excretory  and  Genital  Systems. — The  excretory  system 
consists  of  a  pair  of  dark  colored  glandular  organs  that  lie 
beneath  the  pericardium.  Each  communicates  with  the  peri- 
cardium by  a  small  opening  that  is  not  easy  to  demonstrate 
in  dissections,  and  with  the  cloacal  chamber  by  another  small 
opening. 

By  turning  the  two  gills  (of  Venus)  dorsally  a  very  small 
papilla  may  be  seen,  just  beneath  the  free  border  of  the  inner 
gill,  lying  in  the  cloacal  chamber.    On  the  tip  of  this  papilla 


VENUS  131 

are  two  openings.    The  inner  one  is  the  opening  of  the  ex- 
cretory organ.    The  outer  one  is  the  opening  of  the  genital 

duct. 

The  genital  glands  are  light  colored  organs  that,  during 
the  breeding  season,  extend  through  the  principal  part  of  the 
visceral  mass.  Neither  the  genital  nor  the  excretory  systems 
can  be  profitably  studied  in  a  general  dissection  of  this  form. 
In  Unio  the  excretory  organs  are  more  satisfactory  for  study. 
Do  you  understand  the  supposed  significance  of  their  con- 
nection with  the  pericardium? 

Nervous  System. — 1.  Carefully  remove  the  body  wall 
along  the  side  of  the  esophagus  and  notice  the  cerebral  gang- 
lion of  the  corresponding  side,  This  is  a  rounded,  slightly 
yellow  organ,  about  the  size  of  a  pin  head,  lying  just  pos- 
terior to  the  dorsal  border  of  the  anterior  adductor  muscle. 
(In  Unio  it  is  more  ventral  in  position.)  The  cerebral 
ganglia  of  the  two  sides  are  united  by  a  commissure  that 
passes  anterior  to  the  esophagus.  Two  connectives  leave 
each  cerebral  ganglion.  One  passes  posteriorly  to  join  the 
visceral  ganglion  of  the  corresponding  side.  The  other  passes 
into  the  foot  to  join  the  pedal  ganglion  of  the  corresponding 

side. 

2.  Cut  the  united  lamellae  of  the  inner  gills  ventral  to  the 
posterior  adductor  muscle.  This  will  expose  the  visceral 
ganglia.  They  are  pear-shaped  bodies  lying  just  beneath  the 
posterior  adductor  muscle,  connected  with  each  other  by  a 
short  commissure,  and  connected  with  the  cerebral  ganglia  by 
connectives  that  may  be  traced  a  short  distance  forward 
without  dissection.  A  large  nerve  leaves  the  posterior  end  of 
each  ganglion  and  supplies  the  posterior  end  of  the  corre- 
sponding lobe  of  the  mantle.  Smaller  nerves  go  to  the  pos- 
terior adductor  muscle  and  gills. 

3.  With  a  razor  or  sharp  scalpel  make  a  median  sagittal 
section  of  the  foot,  extending  it  some  distance  into  the  vis- 
ceral mass.  This  will  expose  the  pedal  ganglia,  that  lie  just 
anterior  to  a  loop  of  the  intestine,  and  dorsal  to  the  muscular 


132  MOLLUSCA 

portion  of  the  foot.  The  pedal  ganglia  are  connected  with 
each  other  by  a  broad  commissure  and  with  the  cerebral 
ganglia  by  connectives. 

By  careful  dissection  it  is  possible  to  trace  the  connec- 
tives and  many  of  the  nerves.  The  razor  clam,  Ensis,  is  es- 
pecially favorable  for  dissections  of  the  nervous  system,  as 
the  ganglia,  connectives,  and  many  important  nerves  lie  very 
near  the  surface  and  can  be  seen  without  cutting  the  tissues 
above  them. 

Make  a  drawing,  indicating  the  positions  of  the  ganglia. 

Digestive  System. — This  may  be  traced  by  following  a 
guarded  bristle  that  has  been  inserted  into  the  mouth  of  a 
specimen  that  has  been  killed  in  hot  water  (not  boiling),  or 
by  very  carefully  picking  off  the  tissue  from  one  side.  The 
intestine  where  it  penetrates  the  heart  has  already  been  seen, 
and  may  easily  be  followed  to  the  anus. 

The  general  arrangement  of  the  alimentary  canal  is  well 
shown  by  a  median  sagittal  section  of  a  preserved  specimen. 

The  brownish  digestive  gland,  commonly  called  the 
"liver,"  will  be  seen  surrounding  a  portion  of  the  stomach. 

The  enlargement  on  the  intestine  in  the  posterior  portion 
of  the  pericardium  is  of  unknown  function.  In  some  forms 
a  special  diverticulum  from  the  stomach  bears  a  transparent 
cylindrical  rod,  the  crystalline  style.  This  can  easily  be 
found  in  Mya.  Probably  all  lamellibranchs  have  similar 
structures  more  or  less  well  developed,  but  many  do  not  have 
special  pouches  for  their  formation. 

Draw  the  alimentary  canal.  (This  may  be  included  with 
your  sketch  of  the  nervous  system.) 

Cut  a  preserved  specimen  into  transverse  sections  about 
a  quarter  of  an  inch  thick,  and  place  the  sections  in  their 
proper  order  and  position.  (They  should  be  placed  in  a  dis- 
secting pan  in  very  little  water.) 

Study  these  sections  for  the  arrangement  of  organs.  The 
relation  of  the  gills  to  the  branchial  and  the  cloacal  chambers 
should  be  understood. 


> 

VENUS,    YOLDIA  133 

Make  drawings  of  sections  that  pass  through  the  heart 
and  through  the  posterior  adductor  muscle. 

Belding:  A  Report  upon  the  Quahog  and  Oyster  Fisheries  of  Massa- 
chusetts.   Fish  and  Game  Com.,  Mass.,  1912. 

Howard  and  Anson:  Phases  in  the  Parasitism  of  the  Unionidae.  Jour. 
Parasitology,  9,  1922. 

Lefevre  and  Curtis:  Studies  on  the  Reproduction  and  Artificial  Propa- 
gation of  Fresh-water  Mussels.    Bull.  U.  S.  Bur.  Fish.,  30,  1910. 

Mathews:  The  Palps  of  Lamellibranchs  as  Autonomous  Organs.  Jour. 
Exp.  Zool.,  51,  1928. 

Nelson:  On  the  Origin,  Nature,  and  Function  of  the  Crystalline  Style 
of  Lamellibranchs.     Jour.  Morph.,  31,  1918. 

:    Recent  Contributions  to  the  Knowledge  of  the  Crystalline  Style 

of  Lamellibranchs.    Biol.  Bull.,  49,  1925. 

Smith:  The  Mussel  Fishery  and  Pearl-button  Industry  of  the  Missis- 
sippi River.    Bull.  U.  S.  Fish  Com.,  1898. 

If  time  permits,  it  will  be  desirable  to  become  acquainted 
with  some  of  the  structures  of  theoretic  importance  and  with 
some  of  the  adaptations  of  pelecypods  for  the  lives  they  live. 
For  this  purpose  a  few  forms  have  been  selected,  and  direc- 
tions for  the  study  of  the  particular  parts  in  question  are 
given. 

YOLDIA  LIMATULA 

This  form  belongs  to  the  order  Protobranchia,  and  is  sup- 
posed to  be  one  of  the  most  primitive  of  living  pelecypods. 
It  lives  in  soft  mud,  such  as  is  found  in  quiet  coves  and  bays. 
(It  is  abundant  in  the  Eel  Pond  at  Woods  Hole.)  Although 
it  burrows  in  the  mud,  it  lives  near  the  surface,  and  fre- 
quently has  the  posterior  end  above  the  mud. 

1.  Place  a  specimen  in  a  dish  of  sea  water,  and  notice 
the  movements  and  shape  of  the  foot.  See  if  the  movements 
are  always  alike.  What  would  happen  if  such  movements 
were  made  by  a  specimen  lying  on  soft  mud?  Place  a  speci- 
men on  mud  and  watch  the  results. 

2.  Leave  a  specimen  in  an  aquarium  in  which  two  inches 
of  bottom  mud  has  been  placed,  and  see  if  it  is  feeding  in  the 
morning. 

3.  Place  a  young,  transparent  specimen  in  a  watch  glass 


134  MOLLUSCA 

of  sea  water  and  study  the  parts.  The  foot  has  already  been 
observed.  Its  motions  will  probably  be  seen  again  here.  It 
has  been  considered  a  creeping  organ.  Do  you  find  evidence 
that  confirms  or  opposes  the  view?  With  a  lower  power  of 
the  microscope  study: 

(a)  Palps.  These  are  very  large.  The  outer  palp  on 
each  side  is  provided  with  a  long  appendage  that  may  be 
protruded  from  between  the  valves  of  the  shell.  This  is  the 
feeding  appendage. 

(6)  Gills.  These  are  quite  small  and  are  composed  of 
parallel  plates.  They  are  situated  behind  the  palps,  are  at- 
tached dorsally  by  muscular  membranes  to  the  body  wall,  and 
posteriorly  to  the  wall  that  separates  the  siphons.  They  il- 
lustrate what  is  supposed  to  be  the  most  primitive  type  of 
lamellibranch  gill.  Watch  their  movements  and  see  if  you 
can  determine  how  they  cause  the  jets  of  water  to  leave  the 
cloacal  siphon.  What  reason  is  there  for  forming  such  strong 
jets  of  water? 

(c)  Heart  and  Ganglia.  Nicely  shown  in  such  a  speci- 
men. 

4.  Remove  one  of  the  shell  valves  of  an  adult  specimen 
and  examine  the  organs.  An  elongated  sense  tentacle  occurs 
on  one  or  the  other  side  of  the  base  of  the  branchial  siphon, 
between  the  wall  of  the  siphon  and  the  corresponding  mantle 
lobe. 

A  drawing  of  the  organs  will  prove  profitable. 

Drew:    The  Anatomy,   Habits,   and   Embryology   of   Yoldia   limatula. 

Mem.  Biol.  Lab.  Johns  Hopkins  Univ.,  4,  1899. 
:    The  Life-History  of  Nucula  delphinodonta.     Quart.  Jour.  Mic. 

Sci.,  44,  1901. 
Mitsukuri:    On  the  Structure  and  Significance  of  some  Aberrant  Forms 

of  Lamellibranchiate  Gills.    Quart.  Jour.  Mic.  Sci.,  21,  1881. 

MYTILUS  OR  MODIOLUS  (Mussels) 

These  animals  belong  to  the  order  Filibranchia,  and  show 
comparatively  simple  gills,  as  well  as  interesting  modifica- 
tions  for  their  manner   of   living.     They   live   attached   to 


YOLDIA,    MYTILUS   OR    MODIOLUS  135 

stones,  shells,  piles,  or  even  to  sand  grains,  sometimes  in 
moderately  deep  water,  but  frequently  between  low-  and 
high-tide  marks.  The  two  forms  may  easily  be  distinguished 
by  the  positions  of  their  beaks.  The  beaks  of  Mytilus  form 
the  anterior  end  of  the  shell.  Those  of  Modiolus  are  placed 
a  short  distance  posteriorly.  You  should  visit  "mussel  beds," 
and  see  where  and  how  they  are  attached  and  on  what  they 
must  depend  for  food. 

1.  Place  young  specimens  in  dishes  of  sea  water  and  see 
if  they  will  attach  themselves  by  their  byssal  threads.  (They 
will  generally  require  some  hours.)  If  you  can  get  them  to 
attach  to  slides,  the  attachment  may  be  microscopically  ex- 
amined. 

2.  Test  the  strength  of  the  byssal  threads  of  a  rather  old 
specimen.  Are  they  elastic?  How  would  elasticity  aid  the 
animal  in  remaining  attached? 

3.  Leave  specimens  in  sea  water  for  some  hours,  and  see 
if  they  change  their  positions. 

4.  Notice  the  margins  of  the  mantle.  Are  they  fused? 
Why  are  siphons  not  necessary?  See  if  you  can  find  where 
water  passes  in  and  out. 

5.  Wedge  the  valves  of  a  specimen  apart,  cut  the  adduc- 
tor muscles  (take  note  of  their  relative  size),  and  examine 
the  arrangement  of  organs. 

6.  Find  where  the  byssal  threads  are  attached.  Where 
secreted? 

7.  Notice  the  relatively  small  foot,  and  compare  it  with 
the  powerful  foot  muscles.  Why  are  such  powerful  foot 
muscles  necessary?  How  does  the  foot  function  in  attach- 
ing byssal  threads? 

8.  See  how  the  gills  are  attached  to  the  body.  The  fila- 
ments of  the  gills  of  this  form  are  very  loosely  attached  to 
each  other  by  modified  clumps  of  cilia,  that  represent  the 
interfilamentar  junctions.  Cut  off  a  piece  of  a  gill,  mount  it 
in  sea  water  under  a  cover,  and  examine  with  low  and  high 
powers.     Find  places  where  filaments  are  attached  by  the 


136  MOLLUSCA 

bunches  of  cilia.  Find  places  where  the  cilia  have  pulled 
apart.  Notice  the  size  and  shape  of  the  ostia  and  find  the 
two  kinds  of  movable  cilia. 

9.  This  form  usually  shows  the  way  food  is  gathered 
especially  well.  Place  powdered  carmine  on  the  surface  of  a 
gill  and  see  what  becomes  of  it. 

10.  Notice  the  thickened  condition  of  the  mantle.  The 
gonads  extend  into  it,  and  the  thickening  is  due  to  sexual 
products. 

Drawings  of  the  arrangement  of  the  organs,  and  especially 
of  the  microscopic  structure  of  the  gill,  will  prove  profitable. 

Meisenheimer :     Entwicklungsgeschichte    von    Dreissensia   polymorpha. 
Zeit.  f.  wiss.  Zool.,  69,  1900. 

PECTEN  GIBBUS  BOREALIS  (Scallop) 

This  species  belongs  in  the  order  Pseudolamellibranchia 
and  lives  on  muddy  or  sandy  bottoms,  generally  where  the 
water  is  from  a  few  inches  to  several  fathoms  deep.  It  has 
the  power  of  swimming  well  developed.  At  rest  on  the  bot- 
tom it  always  lies  on  the  right  valve  of  the  shell. 

1.  Do  the  valves  of  the  shell  differ  in  color  or  shape? 

2.  On  each  side  of  the  beak  of  each  valve  is  a  flattened 
projection  frequently  called  an  "ear"  or  "wing."  The  pos- 
terior wing  slopes  backward;  the  anterior,  especially  the  one 
on  the  right  valve,  is  somewhat  separated  from  the  body  of 
the  shell  by  a  notch. 

3.  Place  specimens  in  dishes  of  sea  water,  and  when  they 
have  opened  their  shells  notice: 

(a)  Mantle.  See  if  it  is  sensitive.  How  far  can  it  be 
drawn  back  into  the  shell?  What  muscles  are  used  in  with- 
drawing it?  Why  is  it  necessary  to  withdraw  it?  What  is 
peculiar  about  the  shape  of  the  margin?  What  reason  is 
there  for  this  structure? 

{b)  The  pallial  eyes,  bright  specks  along  the  margins  of 
the  mantle.    Are  they  placed  in  any  order? 

(c)  The  arrangement  of  the  tentacles  on  the  margins  of 


PECTEN,    OSTREA  137 

the  mantle.    Why  should  sense  organs  be  placed  in  this  posi- 
tion? 

4.  Specimens   in   aquaria   will   often   swim.     If   possible, 

notice  how  this  is  accomplished. 

Wedge  the  valves  of  a  specimen  apart  and  notice  the 
single  large  adductor  muscle.  What  need  has  Pecten  for 
such  a  large  adductor?    Notice  the  foot  and  compare  it  with 

the  foot  of  Venus. 

How  are  the  gills  attached  to  the  body?  What  would  be 
the  effect  on  the  gills  if  they  were  attached  to  the  mantle  and 
to  each  other,  as  in  most  forms,  when  water  is  ejected  in 

swimming? 

Examine  the  structure  of  the  gill  and  notice  how  much 
larger  the  interfllamentar  junctions  are  near  the  interlamel- 
lar  junctions  than  elsewhere.  Near  the  margins  of  the  gills 
the  junctions  are  frequently  simple  bunches  of  cilia,  as  in 
Mytilus.  Observe  the  muscular  movements  of  the  gills.  The 
gills  of  this  form  are  muscular  and  can  be  drawn  together 
when  the  animal  swims. 

Drawings  to  show  the  arrangement  of  the  organs  and  the 
structure  of  the  gill  are  desirable. 

Belding:   The  Scallop  Fishery  of  Massachusetts.    Mass.  Fish  and  Game 

Com.,  1910. 
Drew:    The  Habits,  Anatomy,  and  Embryology  of  the  Giant  Scallop, 

Pecten  tenuicostatus.    Univ.  of  Maine  Stud.,  No.  6,  1906. 

OSTREA  VIRGINICA  (Oyster) 

This  also  belongs  to  the  order  Pseudolamellibranchia.  It 
forms  a  good  example  of  adaptation  for  a  sedentary  life.  It 
occurs,  fastened  to  rocks  and  other  shells,  in  positions  where 
it  is  much  exposed  to  attacks  of  the  enemies  of  lamellibranchs. 

1.  Notice  the  difference  in  the  size  and  shape  of  the 
valves.    Why  is  this  desirable? 

2.  Notice  the  thickness  of  the  valves  and  the  complete- 
ness with  which  they  come  in  contact  when  the  shell  is  closed. 
Would  such  a  heavy  or  tight-closing  shell  be  satisfactory  for 
the  scallop  or  the  razor-shell  clam? 


138  MOLLUSCA 

3.  Open  the  shell  by  breaking  the  edge,  inserting  a  knife 
blade  through  the  opening,  and  cutting  the  adductor  muscle 
away  from  the  flattened  right  valve  of  the  shell  and  notice 
the  single  adductor,  extensive  gills,  and  the  absence  of  a  foot. 
The  larval  oyster  has  a  foot,  but  this  is  lost  early  in  life. 

Brooks:    The  Oyster. 

Grave:    Maryland  Shell-Fish  Commission,  4,  Rep.,  1912. 

Horst:    On  the  Development  of  the  European  Oyster   (Ostrea  edulis, 

L.).    Quart.  Jour.  Mic.  Sci.,  22,  1882. 
Nelson:    The  Attachment  of  Oyster  Larvae.    Biol.  Bull.,  46,  1924. 

SOLEMYA 

This  form,  a  member  of  the  order  Protobranchia,  with 
much  the  same  structure  as  Yoldia,  shows  an  interesting 
method  of  swimming  that  should  be  compared  with  Pecten, 
and  with  the  jets  of  water  formed  by  My  a.  Specimens  may 
be  dug  at  low  tide  from  mud  or  sandy  mud,  placed  in  a  dish 
of  sea  water,  and  observed.  Does  the  posterior  opening  in 
the  mantle  chamber  correspond  to  typical  siphons?  See  if 
you  can  find  how  the  animal  swims.  Is  the  movement  con- 
tinuous or  jerky?  Does  the  animal  move  forward  or  back- 
ward? Is  the  foot  active?  Are  jets  of  water  thrown  from 
the  shell?    Is  the  animal  adapted  to  forming  jets  of  water? 

Examine  a  specimen  that  has  the  valves  closely  drawn 
.together  and  see  how  rounded  the  margins  appear.  Examine 
a  shell  from  which  the  animal  has  been  removed  by  macera- 
tion and  see  the  relation  of  the  shell  cuticle  and  the  cal- 
careous portion  of  the  shell.  What  becomes  of  the  marginal 
cuticle  when  the  shell  is  closed?  Can  this  have  anything  to 
do  with  throwing  jets  of  water  from  the  shell? 

Drew:    Locomotion  in  Solenomya  and  its  Relatives.     Anat.  Anz.,  17, 

1900. 
Stempell:    Zur  Anatomie  von  Solemya  togata.     Zool.  Jahrb.,  13,  1899. 

MYA  ARENARIA  (Long  Clam) 

This  animal  belongs  to  the  order  Eulamellibranchia,  as 
does  Venus,  and  is  introduced  because  of  adaptation  for  its 
manner  of  living.    It  lives  buried  in  the  mud,  in  which  as  an 


SOLEMYA,   MYA  139 

adult  it  remains  stationary.  You  should  find  a  "clam  bed" 
along  the  shore,  and  after  noticing  the  pits  in  the  surface  of 
the  mud,  and  the  jets  of  water  that  are  sometimes  thrown 
from  the  pits,  dig  down  and  see  how  the  animals  are  placed. 
If  the  water  is  calm,  find,  at  the  surface  of  the  mud,  the 
openings  of  the  siphons  of  specimens  that  are  still  covered 
by  water.  You  will  need  to  walk  very  carefully  so  as  to 
disturb  mud  and  water  as  little  as  possible,  as  the  siphons 
are  otherwise  closed  and  withdrawn. 

1.  Why  does  this  animal  not  need  a  shell  that  is  as  heavy 
and  closes  as  tightly  as  that  of  Venus?  Does  it  show  the 
same  points  regarding  the  valves  (umbos,  beaks,  lines  of 
growth,  and  ligament)?  Later,  when  the  shell  is  removed, 
the  large  cartilage  pit  on  the  left  valve  will  be  seen. 

2.  The  ventral  borders  of  the  mantle  lobes  are  united  ex- 
cept near  the  anterior  end,  where  there  is  a  space  through 
which  the  foot  may  be  seen. 

3.  The  siphons  are  large  and  muscular  and  may  be  re- 
tracted, as  in  the  specimen  that  you  are  handling,  or  may 
be  greatly  extended,  as  may  sometimes  be  seen  in  aquarium 
specimens.    Why  does  Mya  need  larger  siphons  than  Venus 

does? 

4.  Pick  up  a  specimen  that  has  the  siphons  extended  and 
notice  the  powerful  ejection  of  water.  Is  it  ejected  from  one 
or  both  openings?  How  is  this  accomplished?  Of  what  ser- 
vice can  such  jets  be  to  the  animal?  Why  are  powerful  jets 
of  this  nature  of  more  service  to  Mya  than  to  Venus? 

Notice  the  cartilage  in  the  cartilage  pit  on  the  left  valve. 
What  function  does  it  perform?  Why  is  there  no  need  for  a 
large  and  powerful  foot?  It  is  much  easier  to  trace  the 
alimentary  canal  and  the  ganglion  connectives  in  this  form 
than  in  Venus. 

* 

Belding:    The   Mollusk   Fisheries   of   Massachusetts.     Mass.  Fish   and 

Game  Com.,  1909. 
Kellogg:    Life-History  of  the  Common  Clam,  Mya  arenaria.    Bull.  U. 

S.  Fish  Com.,  1899. 


140  MOLLUSCA 

Mead  and  Barnes:    Observations  on  the  Soft-shell  Clam.    Rhode  Island 

Com.  Inland  Fish.,  20  to  24,  1900  to  1904. 
Yonge:    Studies  on  the  Comparative  Physiology  of  Digestion.    I.  The 

Mechanism  of  Feeding,  Digestion,  and  Assimilation  of  the  Lamelli- 

branch  Mya.    Brit.  Jour.  Exp.  Biol.,  1,  1923. 

ENSIS  DIRECTUS  (Razor-shell  Clam) 

This  species  is  another  representative  of  the  order  Eula- 
mellibranchia  and  is  introduced  because  of  its  adaptation  for 
a  burrowing  habit,  and  because  of  the  great  ease  with  which 
its  nervous  system  can  be  studied.  Individuals  are  not  un- 
common on  mud  or  sand  flats  from  which  the  water  flows 
at  low  tide.  They  may  sometimes  be  seen  protruding  above 
the  surface  of  the  mud,  but  are  hard  to  approach  because 
of  their  great  sensitiveness.  Upon  being  disturbed  they 
quickly  disappear  beneath  the  surface  of  the  mud.  These 
animals  are  sometimes  used  for  food.  They  are  frequently 
collected  in  Japan  by  placing  a  little  common  salt  in  the 
opening  of  the  burrows.  Within  a  few  seconds  an  animal  so 
treated  energetically  backs  out  of  its  burrow. 

1.  Notice  the  shape  of  the  shell,  the  way  it  gapes  at  both 
ends,  and  the  way  the  lobes  of  the  mantle  are  fused. 

2.  With  a  pencil  point  or  seeker  stroke  the  tentacles 
around  the  siphon  openings,  while  the  animal  is  being  held 
anterior  end  downward.  This  will  cause  it  to  perform  the 
burrowing  movements.  Study  the  movements  carefully  and 
see  what  the  effects  would  be  were  they  performed  in  mud. 
Thrust  the  anterior  end  of  the  shell  in  mud  and  watch  the 
result  of  the  movements. 

3.  Water  is  ejected  by  the  sides  of  the  foot  to  aid  in  bur- 
rowing or  to  enable  the  animal  to  swim,  but  observations  on 
its  method  of  ejecting  it  are  not  easily  made,  and  are  sure  to 
take  much  time.  Notice  the  way  the  anterior  margins  of  the 
lobes  of  the  mantle  scrape  mud  from  the  foot  when  the  foot 
is  being  withdrawn. 

4.  With  a  scalpel  separate  the  united  margins  of  the 
mantle  throughout  their  length.  Slowly  pry  the  valves  apart, 
lift  up  the  free  end  of  the  foot  and  pull  it  posteriorly. 


ENSIS,    CUMINGIA  141 

The  cerebral  ganglia  are  plainly  visible  without  further 
cutting.  They  lie  just  posterior  to  the  anterior  adductor 
muscle  and  in  front  of  the  mouth,  and  are  widely  separated. 
They  are  connected  by  a  narrow  commissure,  and  each  gives 
rise  to  a  cerebrovisceral  and  a  cerebropedal  connective  and 
to  a  number  of  nerves.  The  nerves  that  supply  the  anterior 
part  of  the  mantle  and  the  anterior  adductor  muscles  are 
especially  easily  seen. 

5.  If  the  specimen  is  one  that  is  nearly  or  quite  dead,  it 
is  easy  to  dissect  out  the  cerebropedal  connectives  and  the 
pedal  ganglia,  which  are  not  far  from  the  base  of  the  foot 
and  not  deeply  embedded. 

6.  Allow  the  foot  to  return  to  its  normal  position  and  cut 
along  the  line  of  union  of  the  inner  gills.  Without  further 
cutting  the  visceral  ganglia  may  be  studied.  Their  connec- 
tives may  be  followed  easily  as  far  forward  as  the  palps. 
The  posterior  pallial  and  the  branchial  nerves  may  also  be 
seen. 

A  drawing  of  the  nervous  system  should  be  made. 

Drew:    The   Habits  and  Movements   of  the   Razor-shell   Clam,   Ensis 

directus.    Biol.  Bull.,  12,  1907. 
:    The  Physiology  of  the  Nervous  System  of  the  Razor-shell  Clam, 

Ensis  directus.    Jour.  Exp.  Zool.,  5,  1908. 

CUMINGIA  TELLINOIDES 

In  separate  bowls  of  sea  water  place  several  Cumingia 
which  have  been  kept  in  moist  sand  for  a  few  hours.  Watch 
the  shedding  of  eggs  (pinkish)  or  sperm  (whitish)  which 
ordinarily  will  require  at  least  thirty  minutes.  Transfer  30 
to  50  eggs  to  a  Syracuse  dish  containing  clean  sea  water. 
Then  fertilize  them  by  adding  not  more  than  a  very  small 
drop  of  sperm  suspension.  Observe  the  developing  eggs  from 
time  to  time,  noting  when  the  following  stages  occur:  (1) 
Blastula.  Is  this  ciliated?  (2)  Gastrula.  (3)  Trochophore 
larva.     (4)  Veliger  larva. 


142  MOLLUSCA 

AMPHINEURA 
CHAETOPLEURA  (Chiton) 

It  will  be  profitable  to  study  only  external  features,  unless 
time  is  to  be  had  for  cutting  and  studying  sections,  as  the 
species  is  small  and  difficult  to  dissect.  Its  apparently  gen- 
eralized structure,  and  its  adaptations,  make  it  desirable  for 
students  to  understand  from  descriptions  and  figures  the  main 
features  of  its  anatomy. 

1.  Examine  specimens  that  are  attached  to  stones  and 
shells  and  see  how  nicely  they  adapt  their  shapes  to  the 
shapes  of  the  objects  to  which  they  are  attached.  How  is 
this  possible? 

2.  Remove  a  specimen  and  quickly  transfer  it  to  a  clean 
glass  slide,  applying  its  ventral  side  to  the  glass.  Put  your 
finger  in  its  back  and  prevent  it  from  curling  for  a  minute. 
It  will  then  generally  remain  attached  to  the  slide  and  may  be 
studied  from  both  sides. 

3.  How  many  plates  are  there?  What  is  the  shape  of 
each?  Do  they  apparently  join  edge  to  edge  or  do  they 
overlap?  Do  the  plates  extend  clear  to  the  margin  of  the 
animal?  What  reason  is  there  for  having  plates  instead  of 
a  solid  dorsal  shell? 

4.  Notice  the  thickened  margin  of  the  animal,  and  see 
that  dorsally  it  bears  spicules,  while  ventrally  it  is  smooth 
and  is  applied  closely  to  the  slide. 

5.  Notice  the  flattened  elliptical  foot.  Do  you  understand 
how  the  animal  creeps  and  adheres? 

6.  In  front  of  the  foot  is  the  head  fold  in  which  the  mouth 
can  be  seen. 

7.  In  the  furrow  bordering  the  foot  are  the  gills. 

8.  Remove  the  animal  from  the  slide  and  see  how  it  curls 
up.    Try  to  unroll  it.    Explain. 

9.  If  you  care  to  see  the  radula,  the  organ  that  especially 
indicates  affinity  to  the  Gastropoda,  it  can  be  pulled  out  by 
grasping  just  behind  the  mouth   with  pointed   forceps   and 


CHAETOPLEURA,    BUSYCON  143 

pulling  forward.     When  removed  it  may  be  mounted  on  a 
slide  with  water  and  studied  with  the  microscope, 

Haller:     Die   Organisation   der  Chitonen  der  Adria.     Arb.  Zool    Inst 

Wien,  4,  1882;  5,  1884. 
Heath:    The  Development  of  Ischnochiton.     Zool.  Jahrb.,  12   (Anat ) 

1899. 

GASTROPODA 

A  majority  of  the  Gastropoda  have  the  body  protected 
by  a  spirally  wound  shell,  and  crawl  around  by  means  of  a 
flattened  muscular  foot  which  forms  the  ventral  portion  of  the 
body.    • 

Examine  specimens  of  such  active  forms  as  Alectrion 
obsoleta,  A.  trivittata,  and  Melampus,  and  notice: 

1.  The  relation  of  the  animal  to  its  shell  when  retracted 
and  when  extended. 

2.  Movements.  Any  cilia  on  the  foot?  Any  rhythmic 
waves  passing  from  end  to  end?  What  is  the  mechanism  of 
foot  locomotion? 

3.  The  movements  of  the  tentacles  and  proboscis.  What 
do  the  movements  accomplish? 

Touch  a  specimen  and  see  what  positions  the  parts  take 
when  it  retracts  into  the  shell.  If  the  animal  has  an  oper- 
culum see  where  it  is  borne,  and  how  it  fits  into  the  aperture 
of  the  shell. 

BUSYCON  (FULGUR,  SYCOTYPUS)   (Whelk) 

This  large  gastropod  lives  in  comparatively  shallow  water 
and  depends  largely  on  other  Mollusca  for  its  food.  Examine 
a  retracted  specimen  and  see  how  the  shell  is  closed  by  a 
horny  lid,  the  operculum.  Examine  expanded  specimens  in 
aquaria,  and  see  where  the  operculum  is  placed.  What  posi- 
tion must  the  animal  assume  in  the  shell  to  bring  the  oper- 
culum in  position? 

Shell. — A  somewhat  conical  tube,  spirally  wound,  some- 
what like  a  spiral  stairway.    Observe  the  following  parts: 

1.  The  apex,  forming  the  closed  end  of  the  tube. 

2.  The  spire.     How  many  whorls  are  there?     Do  they 


144  MOLLUSC  A 

differ  in  number  in  different  specimens?  In  what  direction 
are  the  whorls  wound?  (Hold  the  apex  toward  you  in  deter- 
mining this  point.)  Examine  old  and  young  specimens  and 
see  if  there  is  evidence  that  the  apex  is  worn  off. 

3.  The  body  whorl    The  one  that  opens  to  the  outside. 

4.  The  columella.  The  axis  around  which  the  whorls  are 
wound.    This  is  best  studied  in  a  broken  shell. 

5.  The  aperture,  which  is  bounded  by  the  inner  lip  on  the 
columellar  side  and  by  the  outer  lip  along  the  free  edge. 

6.  The  siphonal  canal,  which  forms  the  spoutlike  prolonga- 
tion of  the  shell. 

7.  The  lines  of  growth.  What  do  they  represent?  Do 
they  show  evidence  of  injuries  that  have  befallen  the  shell 
during  the  life  of  the  individual? 

8.  The  three  layers  of  which  the  shell  is  composed.  In  a 
broken  shell  notice:  (a)  the  cuticle,  worn  away  from  the 
greater  portion  of  the  shell;  (b)  the  nacre,  smooth  and  lining 
the  inner  surface  of  shell;  (c)  the  middle  layer.  How  can 
three  layers  be  secreted  by  the  mantle? 

Soft  Parts. — Examine  an  animal  that  has  been  removed 
from  its  shell  and  killed  while  more  or  less  expanded1  and 
see  in  what  position  it  was  placed  in  the  shell.  Compare  the 
number  of  whorls  made  by  it  to  the  number  in  the  shell. 
Understand  which  is  right  and  which  is  left  for  the  coiled 
part  of  the  body.  Which  side  was  applied  to  the  columella? 
In  determining  the  position  of  organs,  constantly  keep  the 
sides  in  mind. 

lrThis  can  be  accomplished  by  breaking  the  shell  away  with  the 
blade  of  a  hatchet,  and  when  enough  of  the  shell  has  been  removed, 
loosening  the  muscle  from  the  columella  with  the  thumb,  and  then 
pulling  and  twisting  the  animal  out.  When  free  from  the  shell  place  the 
animal  in  sea  water  to  which  has  been  added  about  one  tenth  its  volume 
of  alcohol  and  a  little  turpentine  (about  10  cc.  of  turpentine  to  each 
100  cc.  of  alcohol)  and  leave  for  several  hours.  An  animal  treated  in 
this  way  will  usually  die  with  its  proboscis  extended.  For  the  method 
we  are  indebted  to  Mr.  Geo.  M.  Gray,  Curator  at  the  Marine  Biological 
Laboratory,  Woods  Hole,  Mass. 


BUSYCON  145 

Before  beginning  the  dissection,  note  the  following  parts: 

1.  The  visceral  dome.  The  portion  that  extended  into  the 
spire  of  the  shell. 

2.  The  mantle,  which  is  thin  and  closely  applied  to  the 
visceral  dome,  and  raised  to  form  a  thickened  collar  that 
extends  entirely  around  the  body  along  a  line  that  corresponds 
to  the  aperture  of  the  shell. 

3.  The  siphon,  which  is  a  spoutlike  prolongation  of  the 
collar.    Into  what  portion  of  the  shell  does  it  fit? 

4.  The  mantle  chamber.  This  can  be  seen  by  raising  the 
edge  of  the  collar  of  the  mantle. 

5.  The  head,  which  forms  an  anterior  prolongation. 

6.  The  tentacles,  forming  two  triangular  projections  on 
the  head. 

7.  The  eyes,  pigmented  spots  on  the  outer  edges  of  the 
tentacles. 

8.  The  proboscis,  which,  when  extended,  protrudes  from 
beneath  the  portion  that  bears  the  tentacles.  What  is  its 
size,  shape,  and  general  appearance?  It  may  be  retracted 
entirely  into  the  body. 

9.  The  mouth,  at  the  end  of  the  proboscis.  The  end  of 
the  odontophore  may  frequently  be  seen  protruding  from  the 
mouth. 

10.  The  foot.  What  is  its  position,  consistency,  color,  and 
shape?     Is  it  slimy? 

11.  The  opening  of  the  pedal  gland,  on  the  sole  of  the  foot. 
Is  the  pedal  gland  well  developed  in  both  sexes?  Do  you 
know  its  function?     (See  Buccinum  by  Dakin,  1912.) 

12.  The  operculum.    Notice  its  position  and  attachment. 

13.  If  the  specimen  is  a  male,  the  large,  somewhat  flat- 
tened and  bent  penis,  a  little  to  the  right  and  posterior  to  the 
right  tentacle. 

A  number  of  organs  may  be  seen  through  the  somewhat 
transparent  mantle.    These  are: 

14.  The  liver,  which  forms  the  first  two  whorls  of  the 
spire.    Notice  its  color. 

10 


146  MOLLUSCA 

15.  The  gonad,  which  is  borne  on  the  dorsal  surface  of  the 
liver,  and  differs  in  individuals  from  red  and  brown  to  yellow. 

16.  The  stomach,  which  lies  on  the  left  (external)  surface 
of  the  liver.  It  is  curved  and  light  colored  and  is  frequently 
rather  indistinct. 

17.  The  kidney,  which  lies  on  the  dorsal  surface,  and  a 
little  to  the  left  side,  on  the  anterior  end  of  the  liver.  It  is 
somewhat  rectangular  in  shape  and  differs  in  color  from  a 
yellowish  brown  to  a  chocolate  color.  The  kidney  is  com- 
posed of  two  parts,  the  large  acinous  portion,  and  the  smaller 
tubuliferous  portion.  The  latter  lies  along  the  left  side  of 
the  former,  by  the  side  of  the  pericardium. 

18.  The  pericardium  lies  to  the  left  of  the  anterior  end  of 
the  kidney.  Through  its  dorsal  wall  the  yellowish  heart  can 
generally  be  seen. 

19.  The  columellar  muscle,  which  attached  the  animal  to 
its  shell  and  enabled  it  to  withdraw,  can  be  traced  to  the  foot. 

20.  If  the  specimen  being  examined  is  a  female,  the  large 
yellowish  nidamental  gland  will  be  seen  near  the  right  side. 

21.  The  large,  brownish  gill  lies  to  the  left  of  the  nida- 
mental gland  in  the  female  and  anterior  to  the  heart. 

22.  The  osphradium  is  a  small,  brownish  organ  to  the  left 
of  the  anterior  end  of  the  gill  and  at  the  base  of  the  siphon. 

23.  The  hypobranchial  gland  is  a  glandular  portion  of  the 
mantle,  to  the  right  of  the  gill  (between  the  gill  and  the  nida- 
mental gland,  in  the  female). 

Make  a  drawing  of  the  animal  as  a  whole,  showing  as 
many  of  the  observed  points  as  possible. 

Open  the  mantle  chamber  by  cutting  the  mantle  along 
the  right  side  of  the  gill  to  the  limit  of  the  cavity,  reflect  the 
flaps,  and  notice  the  position  and  structure  of  the  gill,  osphra- 
dium, hypobranchial  gland  (cut  in  opening  the  mantle 
cavity),  and,  if  the  specimen  is  a  female,  the  nidamental 
gland.  The  opening  of  the  rectum  will  be  seen  at  the  end  of 
a  short  papilla  in  the  right  side  of  the  mantle  cavity.  The 
opening  of  the  nidamental  gland  will  be  seen  on  an  elevation 


BUSYCON  147 

a  little  to  the  right  and  anterior  to  the  anus.  If  possible, 
insert  a  guarded  bristle  into  this  opening  and  see  what  be- 
comes of  it.  Trace  the  oviduct  from  the  ovary  along  the 
columellar  side  of  the  liver.  See  what  becomes  of  it.  Ex- 
amine the  inside  of  the  nidamental  gland  and  see  its  relation 
to  the  oviduct. 

If  the  specimen  is  a  male,  follow  the  vas  deferens  from 
the  testis  to  the  base  of  the  penis. 

Circulatory  System. — Remove  the  thin  membrane  that 
forms  the  roof  of  the  pericardial  chamber. 

1.  The  heart  consists  of:  (a)  the  large,  rounded  ventricle; 
(£>)  the  smaller,  conical,  thin-walled  auricle. 

2.  The  auricle  receives  blood  by  two  vessels.  One,  return- 
ing blood  from  the  gill,  runs  along  the  left  side  of  the  gill  to 
its  posterior  end,  where  it  bends  abruptly  to  the  right  along 
the  margin  of  the  pericardial  cavity,  and  enters  the  auricle. 
The  other  returns  blood  from  the  tubuliferous  portion  of  the 
kidney  and  follows  the  right  side  of  the  pericardium  to  the 
auricle. 

3.  The  gill  receives  its  blood  through  a  vessel  that  borders 
its  right  side.  This  vessel  receives  the  blood  from  a  portion  of 
the  mantle,  and  from  the  large,  acinous  portion  of  the  kidney. 

4.  The  blood  leaves  the  ventricle  by  a  single  vessel,  the 
aorta,  that  almost  immediately  gives  rise  to  the  visceral 
artery  which  supplies  the  visceral  hump.  Trace  its  distribu- 
tion. 

The  aorta  makes  an  abrupt  turn  downward  and  forward 
and  enlarges  to  form  the  secondary  heart  which  lies  alongside 
the  esophagus.  The  course  of  this  vessel  can  be  studied  best 
after  the  completion  of  the  work  on  the  nervous  system. 

The  course  of  general  circulation  is,  beginning  with  the 
heart,  (a)  system,  (£>)  kidney,  (c)  gill,  and  (d)  back  again 
to  the  heart.  What  is  the  advantage  of  such  a  course  of 
circulation  over  the  reverse? 

Draw  a  figure  showing  the  vascular  system. 

Excretory  System. — The  two  portions  of  the  kidney  have 


148  MOLLUSCA 

already  been  noticed.    Cut  along  their  common  line  of  union 
and  examine  the  inner  surface  of  each  part. 

1.  Notice  the  parallel  lines  of  tubules  that  form  the  sub- 
stance of  the  tubuliferous  portion,  and  the  lobules  that  form 
the  comparatively  thick  walls  of  the  acinous  portion. 

2.  Find  the  slitlike  opening  that  leads  from  the  kidney  to 
the  mantle  cavity.  It  is  at  a  point  between  the  two  portions 
of  the  kidney  and  is  easily  found  from  the  mantle  chamber. 
A  small  opening  leads  into  the  pericardium,  but  it  is  hard  to 
find  it  in  dissections. 

Digestive  System. — 1.  Remove  part  of  the  integument  at 
the  base  of  the  proboscis  and  find  the  muscles  that  retract  it. 
How  many  are  there  and  how  are  they  attached?  Do  you 
understand  how  the  proboscis  is  extended? 

2.  With  a  pair  of  scissors  open  the  extended  proboscis 
along  the  ventral  line,  pin  it  open,  and  notice  that  the  exposed 
muscular  mass,  the  buccal  mass,  is  attached  to  the  wall  of  the 
proboscis  in  the  region  of  the  mouth,  at  its  base,  and  by 
means  of  fibers  along  its  sides. 

3.  Push  the  muscular  mass  slightly  to  one  side  and  notice 
the  esophagus,  which  is  closely  applied  to  the  dorsal  wall  of 
the  proboscis.  Notice  the  muscle  fibers  that  extend  from  it 
to  the  proboscis.    What  is  their  function? 

4.  The  odontophoral  apparatus  consists  of  a  forked  car- 
tilage, the  odontophoral  cartilage,  that  is  surrounded  by 
muscles  and  cannot  be  seen  until  these  are  removed,  a  radula 
which  is  for  most  of  its  length  enclosed  in  a  sac,  the  radular 
sac,  and  is  exposed  only  in  the  region  of  the  mouth,  and  the 
muscles  for  moving  the  cartilage  and  the  radula. 

(a)  The  strands  of  muscle  which  run  forward  from  the 
odontophoral  cartilage  to  be  inserted  on  the  walls  of  the  pro- 
boscis are  the  cartilage  protractors. 

(b)  Attached  to  the  ends  of  the  two  horns  of  the  cartilage 
and  running  posteriorly  to  be  attached  to  the  walls  of  the 
proboscis  near  its  base  are  the  flat  cartilage  retractors. 

(c)  Running  lengthwise  of  the  buccal  mass,  on  its  ventral 


BUSYCON  149 

side,  are  three  pairs  of  slender  muscles,  one  pair  median  and 
the  others  covering  the  horns  of  the  odontophoral  cartilage 
that  has  just  been  observed.  Find  to  what  the  muscles  are 
attached  anteriorly  and  posteriorly.  If  the  animal  is  fresh, 
pull  on  the  muscles  or  stimulate  the  nerves  by  pinching  gently 
with  forceps  and  see  what  moves.  These  are  the  radula 
protractors. 

(d)  Beneath  the  radula  protractors  observe  the  sheet  of 
cross  fibers  that  bind  the  horns  of  the  odontophoral  cartilage 
together. 

Make  a  drawing  showing  the  ventral  side  of  the  buccal 

mass. 

(e)  A  portion  of  the  radula  is  visible  near  the  anterior 
end  of  the  proboscis.  Introduce  a  bristle  into  the  esophagus 
and  determine  its  relation  to  the  exposed  radula. 

(/)  Loosen  the  anterior  end  of  the  buccal  mass  from  the 
wall  of  the  proboscis,  turn  it  back  and  see  how  the  radula 
passes  around  the  odontophoral  cartilage.  With  a  hand  lens 
notice  the  teeth  on  the  open  radula,  ventral  to  the  cartilage, 
and  see  how  the  radula  is  folded  as  it  passes  over  the  dorsal 
side  of  the  cartilage  so  the  teeth  are  turned  in.  What  func- 
tion does  this  serve? 

(g)  Cut  the  cartilage  protractors  and  reflect  the  buccal 
mass.  It  is  attached  to  the  wall  of  the  proboscis  at  its  pos- 
terior end  by  strong  muscles,  the  radula  retractors.  These 
may  be  studied  after  cutting  the  sheath  of  cross  fibers  that 
hold  the  mass  together.  Determine  how  they  are  attached  to 
the  sides  of  the  radula.    Why  do  they  need  to  be  so  powerful? 

Make  a  drawing  oj  the  buccal  mass  as  seen  from  the 
dorsal  side. 

(h)  Pull  away  the  muscles  and  examine  the  shape  of  the 
odontophoral  cartilage  and  its  relation  to  the  radula. 

(i)  Remove  the  radula,  unfold  it,  and  examine  it  micro- 
scopically. Do  the  teeth  differ  in  any  way  at  the  two  ends? 
Why  is  the  radula  so  long? 

Draw  a  portion. 


150  MOLLUSC  A 

5.  In  a  living  Busy  con  removed  from  its  shell  and  par- 
tially anesthetized  (by  the  addition  of  chloroform  to  the  sea 
water),  observe  the  activity  of  the  radula.  Any  student 
who  has  already  completed  the  dissection  of  the  radula  in 
the  injected  specimen  may  make  a  special  dissection  of  the 
odontophoral  apparatus,  utilizing  this  fresh  material.  Fol- 
low directions  as  given  in  section  4,  page  148.  After  exposing 
the  various  muscles  and  nerves  these  may  be  stimulated  by 
pinching  gently  with  forceps  or  by  pulling  the  muscles.  In 
this  way  a  clear  idea  of  the  function  of  the  muscles  may  be 
obtained. 

The  radula  is  the  organ  upon  which  most  gastropods  de- 
pend for  getting  food.    You  should  understand  how: 

1.  The  proboscis  is  protruded  and  retracted. 

2.  The  odontophoral  cartilage  is  protruded  and  retracted. 

3.  The  radula  is  protracted  and  retracted.  By  means  of 
a  binocular  dissecting  microscope  note  its  action  in  a  living 
crepidula. 

4.  The  radula  is  folded  by  the  cartilage  and  spread  for 
action. 

5.  The  food  is  torn  off  and  taken  into  the  mouth. 
Near  the  base  of  the  proboscis  is  a  pair  of  large,  yellow 

salivary  glands,  the  ducts  from  which  extend  on  either  side  of 
the  esophagus  to  the  mouth.  Further  back,  on  the  right  side 
of  the  esophagus,  is  the  small  pancreas. 

After  studying  the  nervous  system,  trace  the  esophagus 
to  the  stomach  and  the  intestine  to  the  anus. 

Nervous  System. — Most  of  the  ganglia  are  grouped  around 
the  esophagus,  about  three  quarters  of  an  inch  posterior  to 
the  base  of  the  proboscis.  They  are  all  brown  and  accord- 
ingly conspicuous.  Carefully  cut  around  its  base  so  the  pro- 
boscis may  be  turned  back,  and  the  ganglia  on  the  ventral 
surface  of  the  esophagus  may  be  seen.  Carefully  pick  away 
the  tissue  that  covers  the  ganglia  and  notice  on  the  ventral 
side  of  the  esophagus: 

1.  The  small  but  conspicuous  buccal  ganglia.     These  are 


BUSYCON 


151 


united  with  each  other  and  with  the  cerebral  ganglia  and 
send  nerves  to  the  mouth  apparatus. 

2.  The  large  pedal  ganglia,  fused  together  but  distinctly- 
paired,  lying  posterior  to  the  buccal  ganglia  and  sending 
nerves  to  the  two  sides  of  the  foot.  Each  is  united  by  con- 
nectives with  the  corresponding  cerebral  and  pleural  ganglia. 

From  the  dorsal  side  a  number  of  ganglia  may  be  seen, 
more  of  which  lie  to  the  right  than  to  the  left  of  the  median 

line. 

1.  On  the  left  side  there  are  two  ganglia  that  are  in 
rather  close  union  with  each  other.  The  most  anterior,  the 
left  cerebral,  is  the  larger  of  the  two.  The  left  pleural  joins 
it  posteriorly  and  ventrally  and  extends  nearly  to  the  ventral 
side  of  the  esophagus. 

2.  On  the  right  side  four  ganglia  may  be  distinguished. 
The  right  cerebral  and  right  pleural  are  fused  to  form  one 
mass,  but  there  is  a  marked  constriction  between  them.  Pos- 
teriorly and  dorsally  the  right  pleural  is  connected  by  a  con- 
nective with  the  right  parietal  (supra-intestinal),  which  lies 
very  close  to  it.  The  remaining  ganglion,  the  left  parietal 
(subintestinal) ,  which  is  almost  in  contact  with  the  right 
pleural  and  right  pedal  ganglia,  lies  ventrally  and  to  the 
right  of  the  right  parietal  ganglion.  It  is  connected  with 
the  left  pleural  ganglion  by  a  connective  that  runs  behind  the 
pedal  ganglia.  There  seems  also  to  be  a  connection  with  the 
right  pleural  ganglion,  but  this  must  be  considered  a  secon- 
dary connection.  Do  you  understand  how  this  ganglion  comes 
to  have  this  position? 

3.  Another  ganglionic  mass,  the  visceral  ganglion,  possi- 
bly formed  by  the  fusion  of  two  ganglia,  lies  just  below  the 
external  opening  of  the  kidney,  where  it  can  be  seen  as  a 
brown  mass  through  the  body  wall.  It  lies  on  the  elongated 
commissure  that  connects  the  two  parietal  ganglia.  The  com- 
missure may  be  followed  by  dissection. 

The  cerebral  ganglia  are  the  most  centralized.  Besides 
being  connected  with  each  other  by  a  commissure  dorsal  to 


152  MOLLUSC  A 

the  esophagus,  and  being  intimately  connected  with  the 
pleural  ganglia,  each  cerebral  ganglion  is  connected  with  the 
corresponding  buccal  and  pedal  ganglion  and,  through  the 
pleural,  with  the  parietal  ganglion.  The  parietal  ganglia  are 
connected  with  each  other  by  a  long  commissure  on  which  the 
visceral  ganglion  is  placed.  Each  pedal  ganglion  receives  con- 
nectives from  the  cerebral  and  from  the  pleural  ganglion  of 
the  corresponding  side. 

Draw  figures  of  the  nervous  system  and  compare  them 
with  the  clay  model.1 

The  dissections  of  the  circulatory  and  digestive  systems 
may  now  be  completed. 

Colton:    How  Fulgur  and  Sycotypus  Eat  Oysters,  Mussels,  and  Clams. 

Proc.  Acad.  Nat.  Sci.,  Philadelphia,   1908. 
Conklin:    The  Embryology  of  Fulgur:    A  Study  of  the  Influence  of 

Yolk  on  Development.    Proc.  Acad.  Nat.  Sci.,  Philadelphia,  1907. 

:    The  Embryology  of  Crepidula.     Jour.  Morph.,  13,  1897. 

Copeland:    The  Olfactory  Reactions  and  Organs  of  the  Marine  Snails, 

Alectrion  obsoleta  and  Busycon  canaliculatum.    Jour.  Exp.  Zool.,  25, 

1918. 
:    Locomotion  in  Two  Species  of  the  Gastropod  Genus  Alectrion 

with  Observations  on  the  Behavior  of  Pedal  Cilia.     Biol.  Bull.,  37, 

1919. 
Crozier:  On  the  Use  of  the  Foot  in  Some  Mollusks.    Jour.  Exp.  Zool., 

27,  1919. 
Dakin:    Buccinum.    Liverpool  Marine  Biol.  Com.  Memoir  No.  20,  1912. 
Glaser:    tiber  den  Kannibalismus  bei  Fasciolaria  tulipa   (var  distans) 

und  deren  larvale  Excretionsorgane.    Zeit.  f.  wiss.  Zool.,  80,  1905. 
Herrick:     Mechanism    of   the    Odontophoral   Apparatus   in   Sycotypus 

canaliculars.     Am.  Nat.,  40,   1906. 
Olmstead:    Notes  on  the  Locomotion  of  Certain  Bermudian  Mollusks. 

Jour.  Exp.  Zool.,  24,  1917. 
Orton:     An   Account   of   the   Natural    History    of   the  Slipper-Limpet 

(Crepidula  fornicata).     Jour.  Marine  Biol.  Assoc,  9,  1912. 
Parker:    The  Mechanism  of  Locomotion  in  Gastropods.    Jour.  Morph., 

22,  1911. 
Patten:    The  Embryology  of  Patella.    Arb.  Zool.  Inst.  Wien,  6,  1886. 

1  Instructors  will  find  that  a  model  prepared  by  sticking  lumps  and 
strands  of  modeling  clay  on  a  cylindrical  graduate  to  illustrate  the  posi- 
tions of  the  ganglia  and  connectives  on  the  esophagus  will  greatly  aid 
the  students. 


BUSYCON,    LOLIGO  153 

CEPHALOPODA 
LOLIGO  PEALEI  (The  Squid) 

Specimens  of  this  or  closely  related  species  are  rather 
common  along  the  Atlantic  coast  of  the  United  States.  They 
are  active  swimmers,  but  may  occasionally  be  seen  in  shallow, 
quiet  water  near  the  shore.  The  movements  and  positions  of 
adult  specimens  in  aquaria  should  be  studied.  Do  you  know 
what  they  eat  and  how  they  capture  their  food? 

Study  a  small  living  specimen  in  a  jar  of  sea  water  and 
notice: 

1.  Its  general  shape  and  distinct  head. 

2.  Its  position  in  the  water.  For  convenience,  the  lower 
surface  may  be  referred  to  as  ventral,  but  this  is  not  to  be 
considered  as  morphologically  the  same  as  the  ventral  surface 
of  other  Mollusca.  What  parts  are  kept  moving?  Why  is 
water  pumped  when  the  animal  is  not  swimming? 

3.  In  what  direction  can  it  swim  best?  Can  it  swim  in  the 
other  direction?  How  does  it  swim?  Is  the  funnel  movable? 
How  does  it  guide  its  movements? 

4.  Its  color.  Irritate  it  and  see  what  happens.  What  pur- 
pose does  the  change  in  color  serve?    What  is  the  ink  for? 

5.  What  happens  when  the  end  of  a  finger  is  placed  within 
the  circlet  of  tentacles  of  an  animal  about  two  inches  long 
that  is  being  held  firmly? 

Using  an  adult  specimen,  observe: 

1.  The  arrangement  of  the  arms  on  the  head.  Are  they 
arranged  in  any  definite  order?    Are  they  all  alike? 

2.  The  suckers  of  the  arms.  Do  they  follow  the  same 
order  on  all  of  the  arms? 

3.  The  structure  of  a  sucker.  "  Notice  the  peduncle,  outer 
thin  margin,  horny  ring,  and  piston.  Is  the  horny  ring 
smooth?  What  is  its  function?  How  does  the  sucker  work? 
Split  one  and  draw  the  cut  surface. 

4.  The  mouth.  Where  is  it  placed?  Notice  the  tips  of  the 
horny  beak.    Which  jaw  is  the  longest? 

5.  The  eyes. 


154  MOLLUSC  A 

6.  The  fold  of  tissue  behind  each  eye.  These  have  been 
called  the  olfactory  organs,  but  there  is  no  experimental  evi- 
dence of  function. 

7.  The  small  pore  in  front  of  the  eye,  the  aquiferous  pore. 
With  what  does  this  communicate? 

8.  The  attachment  of  the  head  and  the  extent  of  the  man- 
tle opening  around  the  neck. 

9.  The  funnel  protruding  from  beneath  the  mantle  on  the 
ventral  surface.  Notice  the  position  and  character  of  its 
opening. 

10.  The  median  dorsal  projection  of  the  mantle. 

11.  The  tail  fin,  its  position  and  shape.  What  is  its  func- 
tion? 

Draw  the  animal  as  seen  from  the  ventral  side. 
Carefully  open  a  specimen  by  cutting  through  the  mantle 
a  little  to  one  side  of  the  midventral  line. 
Notice : 

1.  The  thickness  and  character  of  the  mantle  and  its  rela- 
tion to  the  rest  of  the  body.  Why  does  it  need  to  be  so 
muscular? 

2.  The  arrangement  of  the  funnel.  Why  does  it  have  a 
thin  posterior  edge?  How  is  it  held  in  position  against  the 
mantle?  Does  it  have  a  valve?  Is  the  funnel  movable  in 
the  living  animal?    Is  there  any  provision  for  movement? 

3.  The  free  edge  of  the  mantle  and  its  relation  to  the  folds 
beneath  the  eyes.  Do  you  understand  how  the  water  gets 
into  and  out  of  the  mantle  cavity? 

4.  The  large  retractor  muscles  of  the  funnel.  How  many 
are  there?  How  can  the  funnel  be  pointed  in  different  direc- 
tions?   What  need  is  there  for  such  a  provision? 

5.  The  retractor  rnuscles  of  the  head.  How  many  are 
there?    Are  they  used  in  swimming  in  any  way? 

6.  The  rectum,  opening  near  the  base  of  the  funnel  be- 
tween two  small  lateral  flaps  of  tissue. 

7.  The  ink  bag,  dorsal  to  the  rectum  and  opening  into  it 
near  the  anus. 


LOLIGO  155 

8.  The  gills,  extending  from  a  point  about  midway  of  the 
body  toward  the  free  edge  of  the  mantle.  How  many  are 
there?  How  are  they  attached?  Why  does  an  animal  that 
is  not  swimming  continually  pump  water  through  the  mantle 
chamber? 

9.  The  branchial  hearts,  at  the  bases  of  the  gills,  rounded, 
light  colored  organs  than  can  be  seen  through  the  membrane 
covering  them. 

10.  The  median  ventral  mesentery. 
If  the  specimen  is  a  male,  notice: 

1.  The  slender,  tapering  penis,  to  the  left  of  the  rectum. 

2.  The  kidneys,  white  organs  to  be  seen  through  the  mem- 
branous covering,  between  the  bases  of  the  gills.  From  this 
position  they  taper  anteriorly  for  half  an  inch  or  more  and 
send  small  lobes  posteriorly. 

3.  The  openings  of  the  kidneys  near  their  anterior  ends,  on 
small  papillae. 

4.  The  conical  posterior  portion  of  the  viscera.  This  is 
composed  of  a  large  visceral  sac  and  portions  of  the  sexual 
organs. 

Draw  the  animal,  showing  the  points  observed. 

If  the  animal  is  a  female,  notice: 

1.  The  pair  of  large,  white  nidamental  glands  that  cover  a 
portion  of  the  rectum  and  the  greater  part  of  the  ink  bag. 

2.  The  openings  of  these  glands  at  their  anterior  ends.  Do 
you  know  the  function  of  these  glands? 

3.  The  small  accessory  nidamental  glands  just  anterior  to 
the  nidamental  glands.  These  have  large  ventral  openings. 
Just  before  egg  laying  they  become  brilliantly  red. 

4.  The  opening  of  the  oviduct  ^dorsal  to,  and  a  little  to  the 
left  of,  the  left  nidamental  gland. 

5.  The  rounded  swelling,  the  oviducal  gland  on  the  oviduct. 

6.  The  mass  of  eggs  that  fills  the  posterior  portion  of  the 
body.    These  are  in  the  ovary  and  oviduct. 

Draw  the  animal,  showing  the  points  observed. 
Excretory  System. — If  the  animal  is  a  female,  remove  the 


156  MOLLUSCA 

nidamental  glands,  and  the  kidneys  will  be  seen  in  the  posi- 
tion described  for  the  male.    The  kidneys  consist  of: 

1.  The  white,  somewhat  triangular,  glandular  portions  al- 
ready noticed,  extending  from  the  region  of  each  branchial 
heart  anteriorly,  and  forming  a  portion  of  the  walls  of  the 
precavae. 

2.  Thef  cavities  of  the  organs  lying  ventrally,  and  at  the 
sides  of  the  glandular  portions. 

3.  The  external  openings,  at  the  ends  of  small  papillae,  on 
either  side  of  the  rectum  near  the  anterior  ends  of  the  kidneys. 

Digestive  System. — Remove  the  funnel  and  its  retractor 
muscles  and  carefully  lay  the  head  open,  along  the  ventral 
side. 

Find: 

1.  The  buccal  mass.  This  is  a  rounded,  muscular  organ, 
with  a  double  ring  of  tissue,  the  buccal  membranes,  at  its 
anterior  end,  that  surrounds  the  horny  jaws.  Examine  the 
jaws  and  see  which  is  the  larger. 

2.  Behind  the  buccal  mass  are  the  paired  salivary  glands. 

3.  Trace  the  narrow  esophagus  from  the  posterior  end  of 
the  buccal  mass  backward.  At  the  base  of  the  head  it  enters 
the  liver,  a  large,  white  organ  that  lies  between  the  retractor 
muscles  of  the  head,  and  extends  from  the  base  of  the  head  to 
a  point  dorsal  to  the  external  openings  of  the  kidneys.  Ly- 
ing close  to  the  esophagus  and  covered  by  the  anterior  end  of 
the  liver  is  an  elongated  median  salivary  gland,  the  duct  from 
which  follows  the  esophagus  into  the  head.  The  esophagus 
leaves  the  liver  about  midway  of  its  length,  and  follows  along 
the  ventral  surface  nearly  to  the  stomach.  Before  entering 
the  stomach  the  esophagus  passes  the  pancreas,  a  white,  lobed 
organ  that  lies  just  above  the  glandular  portion  of  the  kid- 
neys, and  the  systemic  heart,  a  roughly  diamond-shaped  organ 
that  lies  between  the  branchial  hearts. 

The  stomach  proper  is  a  rather  small,  thick-walled  sac 
that  lies  on  the  right  side  of  the  body,  dorsal  and  posterior 
to  the  right  branchial  heart.    From  the  left  side  of  the  stom- 


LOLIGO 


157 


ach  a  rather  large  opening  leads  into  a  thin-walled  blind  sac, 
the  visceral  sac.  The  latter,  when  filled  with  partly  digested 
food,  as  it  frequently  is,  extends  posteriorly  to  the  end  of  the 
body  and  occupies  a  considerable  part  of  the  conical  portion 
of  the  body.  When  empty,  it  is  quite  small  and  incon- 
spicuous. | 

The  intestine  leaves  the  stomach  very  near  the  point  where 
the  esophagus  enters,  and  just  anterior  to  the  opening  that 
leads  into  the  visceral  sac.  It  passes  ventrally,  and  becomes 
visible  from  the  surface,  where  its  position  has  already  been 
noted. 

Draw  a  figure  showing  the  digestive  system. 

Cut  a  median  sagittal  section  of  the  buccal  mass,  and 
notice  the  mouth  cavity,  the  jaws,  the  muscles  that  move 
the  jaws,  the  tongue,  and  the  position  of  the  radula.  Is  the 
radula  arranged  in  the  strap-over-pulley  manner  that  it  is  in 
Busyconf 

Draw  a  figure  of  the  section. 

Male  Reproductive  System. — 1.  The  testis  (morphologic- 
ally the  left)  is  large,  white,  and  flattened,  and  lies  far  back 
in  the  pointed  end  of  the  body.  It  is  enclosed  in  a  sheath 
which  serves  to  collect  the  liberated  sperm. 

2.  Just  anterior  to  the  testis  is  a  small  rounded  vesicle, 
the  ampulla,  which  is  the  point  of  origin  of  the  vas  deferens. 

3.  The  vas  deferens  is  a  plaited  slender  tube,  which  being 
packed  with  sperm  is  opaque  white.  It  extends  from  the  am- 
pulla along  the  right  side  of  a  large  sac  to  be  referred  to  later, 
the  spermatophoric  sac,  to  and  beneath  (dorsal  to)  the  sper- 
matophoric  organ,  where  it  joins  a  portion  of  the  organ  on  its 
left  side  about  one  third  the  length  of  the  organ  back  from 
its  anterior  end.  Remove  the  left  gill  and  branchial  heart  and 
strip  away  the  thin  tissue  that  covers  the  vas  deferens  and 
spermatophoric  organ,  being  careful  not  to  injure  either. 
Carefully  lift  the  right  ventral  side  of  the  spermatophoric 
organ  and  see  where  the  vas  deferens  enters  it.  Drop  the 
spermatophoric  organ  into  position  again. 


158  MOLLUSC  A 

4.  The  spermatophoric  organ  lies  almost  on  the  left  side, 
but  a  little  ventrally.  In  it  the  spermatophores  are  formed. 
It  consists  of  a  series  of  glands  and  mechanical  arrangements 
that  secrete  and  wind  materials  into  spermatophores.  It  con- 
sists of  a  number  of  parts. 

(a)  On  the  right  dorsal  side,  the  part  joined  by  the  vas 
deferens,  is  the  mucilaginous  gland.  This  consists  of  two 
parts. 

(b)  The  ejaculatory  apparatus  gland  extends  from  the 
mucilaginous  gland  posteriorly  and  then  ventrally.  Both  ends 
of  this  gland  are  marked  by  constrictions. 

(c)  From  this  gland  forward  to  a  narrow  duct  is  the 
middle  tunic  gland. 

(d)  The  narrow  duct  leads  into  a  large  blind  pouch  and  is 
the  outer  tunic  gland. 

(e)  The  large  blind  pouch  extends  posteriorly  nearly  the 
length  of  the  organ  and  is  the  hardening  gland. 

(/)  A  branch  leaves  the  narrow  duct  just  before  it  enters 
the  hardening  gland  that  leads  to  the  curved  anterior  extrem- 
ity of  the  gland.    This  is  the  finishing  duct. 

(g)  The  finishing  duct  leads  to  the  curved  gland  men- 
tioned, the  finishing  gland. 

This  completes  the  spermatophoric  organ,  although  some 
minor  structures  have  not  been  mentioned.  A  section  across 
the  ejaculatory  apparatus  gland  will  show  a  large  ridge  with 
a  groove  along  one  side  through  which  the  spermatophore 
travels  and  rotates  while  being  formed. 

5.  From  the  last  part  of  the  spermatophoric  organ,  the 
finishing  gland,  a  straight  duct  leads  posteriorly  by  the  side  of 
the  vas  deferens  to  join  the  spermatophoric  sac  about  the 
length  of  a  spermatophore  from  its  posterior  end.  This  is 
the  spermatophoric  duct. 

6.  The  spermatophoric  sac  is  somewhat  spindle  shaped, 
usually  filled  with  spermatophores,  and  joins  the  base  of  the 
penis. 

Make  a  drawing  of  the  system. 


LOLIGO  159 

Open  the  spermatophoric  sac  and  remove  some  of  the 
spermatophores.  If  the  specimen  has  not  been  preserved 
place  them  immediately  in  10  per  cent  formalin  or  stronger 
to  keep  them  from  ejaculating.  Mount  under  a  cover  and 
examine.  The  specimens  may  be  stained  with  dilute  Ehrlich's 
triacid  stain  and  mounted  in  glycerin  jelly  if  preferred. 
Notice : 

1.  The  spermatophore  is  covered  by  a  transparent  elastic 
outer  tunic  which  has  a  cap  and  cap  thread  at  the  smaller, 
oral  end. 

2.  Inside  this  is  the  somewhat  granular  middle  tunic, 
which  is  much  thicker  at  the  aboral  end. 

3.  The  contents  consist  of  the  aboral  sperm  mass,  the  oral 
ejaculatory  apparatus,  and  the  cement  body,  which  lies  be- 
tween them. 

4.  The  sperm  mass  may  be  seen  to  consist  of  a  closely 
wound  thread.  It  is  actually  covered  by  a  very  thin  inner 
tunic  which  is  separated  from  the  outer  tunic  by  a  space  filled 
with  liquid. 

5.  The  cement  body  is  attached  to  the  sperm  mass  by  a 
narrow  core  and  is  covered  by  a  continuation  of  the  inner 
tunic.  It  is  flask  shaped,  with  the  narrow  end  pointing 
orally. 

6.  The  neck  of  the  cement  body  is  covered  by  parts  of  the 
ejaculatory  apparatus  and  the  bulge  of  the  body  is  joined 
and  possibly  covered  by  the  outer  membrane,  which  with  the 
inner  tunic  forms  the  outer  covering  of  the  ejaculatory  ap- 
paratus that  appears  as  a  double  membrane.  Inside  the  outer 
membrane  is  the  rather  thick  middle  membrane,  the  aboral 
end  of  which  encloses  the  neck  of  the  cement  body  and  ends 
against  the  bulge  of  the  cement  body,  and  the  oral  end  of 
which  is  thrown  into  bends  and  loops  and  is  finally  attached 
to  the  cap  end  of  the  outer  case.  Inside  the  middle  membrane 
is  the  thin  inner  membrane  and  the  spiral  filament  which  en- 
close a  narrow  lumen. 

7.  In  ejaculating,  the  ejaculatory  apparatus  turns  wrong 


160  MOLLUSCA 

side  out  and  the  cement  body  and  sperm  mass  are  crowded 
down  the  tube  thus  formed  by  the  elastic  force  of  the  outer 
tunic  and  the  elastic  and  osmotic  action  of  the  middle  tunic. 

The  sperm  mass  is  forced  into  a  sac  composed  of  the  in- 
verted inner  tunic  and  outer  membrane,  which  remain  at- 
tached to  the  bulge  of  the  cement  body;  the  cement  body  is 
ruptured  and  the  cement  spread  over  the  closed  end  of  this 
sac.    The  reservoir  is  now  ready  to  stick  in  position. 

Studying  the  method  of  ejaculation  is  time  consuming. 
Fresh  specimens  placed  in  about  one-fourth  saturated  solu- 
tion of  magnesium  chloride  for  ten  minutes  or  more  will  be 
slowed  in  action  so  the  process  can  be  followed  more  readily. 
Remove  a  specimen  from  this  solution  to  sea  water,  grasp 
the  cap  thread  with  forceps,  and  shake  the  spermatophore. 
This  should  start  ejaculation.  Ejaculation  can  be  stopped 
promptly  by  squirting  full  strength  formalin  on  the  ejacula- 
tory  aparatus. 

Make  a  drawing  of  a  spermatophore. 

Spermatophores  are  carried  into  position  by  the  action  of 
the  left  ventral  arm  of  the  male.  Examine  its  tip  and  notice 
the  modification  of  the  suckers. 

Female  Reproductive  System. — The  opening  of  the  oviduct 
has  already  been  noticed.    Observe: 

1  The  large,  swollen  portion,  the  oviducal  gland,  that  lies 
on  the  oviduct  dorsal  to  the  left  branchial  heart. 

2.  The  long  convoluted  oviduct  extending  posteriorly  from 
the  oviducal  gland.  It  is  frequently  filled  with  eggs  for  the 
greater  part  of  its  length. 

3.  The  lighter  colored,  greatly  lobulated  ovary,  also  fre- 
quently filled  with  eggs,  lying  dorsal  to  the  oviduct  and  vis- 
ceral sac  and  extending  from  the  region  of  the  stomach  to 
the  end  of  the  body.  The  ovary  is  inclosed  in  a  capsule  from 
which  the  oviduct  leads. 

4.  The  nidamental  and  accessory  nidamental  glands  have 
been  studied  and  removed. 

5.  On  the  median  line  of  the  inner  surface  of  the  outer 


LOLIGO  161 

buccal  membrane  of  the  female  is  the  sperm  receptacle.  Dur- 
ing the  summer  this  is  usually  filled  with  sperm,  and  is,  ac- 
cordingly, white  and  conspicuous.  Below  the  receptacle  is  a 
modified  area  for  the  attachment  of  sperm  reservoirs  as  they 
are  delivered  from  the  spermatophores. 

Draw  a  figure  of  the  female  reproductive  system. 

Circulatory  System. — An  injected  specimen  is  desirable. 
The  blood  that  has  been  supplied  to  the  body  in  general  is 
collected  by  veins  and  carried  to  the  branchial  hearts.  The 
vessels  that  collect  the  blood  are: 

1.  The  precavae.  A  single  vessel  carries  the  blood  from 
the  head  to  the  anterior  ends  of  the  kidneys.  Here  the  ves- 
sel divides  into  right  and  left  precavae  that  are  intimately 
connected  with  the  kidneys.  The  precavae  diverge  near  the 
posterior  ends  of  the  kidneys  and  enter  the  corresponding 
branchial  hearts. 

2.  The  postcavae.  A  pair  of  very  large  vessels  that  return 
blood  from  the  posterior  end  of  the  body.  They  join  the  cor- 
responding precavae  near  the  anterior  borders  of  the  branchial 
hearts. 

3.  The  mantle  veins.  These  return  blood  to  the  branchial 
hearts  from  the  anterior  portion  of  the  mantle. 

The  blood  that  is  received  by  each  branchial  heart  is  sent 
into  the  corresponding  gill  through  a  branchial  artery  that 
leaves  the  heart  near  the  opening  of  the  mantle  vein,  and 
runs  along  the  side  of  the  gill  that  is  attached  to  the-  mantle. 

The  blood  is  collected  from  each  gill  by  a  large  branchial 
vein  that  runs  along  the  ventral  side  of  the  gill,  and  enters 
the  systemic  heart. 

Draw  a  figure  showing  the  ^vessels  connected  with  the 
branchial  hearts. 

Expose  the  systemic  heart  by  carefully  removing  the 
superficial  tissue  between  the  branchial  hearts,  and  notice  that 
it  is  not  symmetrical.  Its  lateral  angles  receive  the  branchial 
veins  and  it  gives  rise  to  an  artery  from  each  of  the  other 
two  angles. 
11 


162  MOLLUSC  A 

1.  The  posterior  aorta  divides  almost  immediately  into 
three  large  vessels.    These  are: 

(a)  The  median  mantle  artery  which  follows  the  edge  of 
the  ventral  mesentery  to  the  mantle. 

(b)  A  pair  of  lateral  mantle  arteries  which  diverge  poste- 
riorly and  supply  the  two  sides  of  the  mantle.  Besides  these 
large  vessels  there  is  a  small  vessel  that  runs  anteriorly  over 
the  ventral  surface  of  the  heart  and  supplies  the  ink  gland 
and  rectum,  and  another  one  that  runs  dorsally  and  poste- 
riorly to  supply  part  of  the  reproductive  system. 

2.  From  the  dorsal  surface  of  the  heart,  near  its  anterior 
end,  a  small  vessel  passes  over  the  anterior  and  dorsal  sur- 
faces of  the  stomach  and  finally  passes  into  the  gonad. 

3.  The  anterior  aorta  is  larger  than  the  posterior  aorta. 
From  the  anterior  angle  of  the  heart,  which  is  to  the  right  of 
the  median  line,  it  follows  a  straight  course  alongside  the 
esophagus  to  the  head.  A  number  of  small  vessels  are  given 
off  along  its  course,  and  it  is  finally  distributed  to  the  head 
and  arms. 

Draw  the  vessels  connected  with  the  systemic  heart,  into 
the  figure  you  have  just  made. 

Nervous  System. — The  stellate  ganglia  may  be  seen 
through  the  transparent  lining  of  the  mantle,  on  either  side 
of  the  neck,  where  the  body  joins  the  mantle.  They  send 
nerves  to  the  mantle  and  are  joined  to  ganglia  in  the  head 
(the  infra-esophageal)  by  connectives.  Why  does  the  mantle 
need  such  large  special  ganglia?  Other  small  ganglia  are 
situated  in  the  body,  but  the  large  and  important  ones  are 
grouped  in  the  head,  where  they  are  supported  and  protected 
by  cartilages. 

With  a  razor  make  a  median  sagittal  section  of  the  head 
of  a  squid  and  notice: 

1.  Dorsal  to  the  esophagus  a  rounded  mass,  the  supra- 
esophageal  ganglion,  which  is  supposed  to  represent  the  fused 
cerebral  ganglia. 

2.  Ventral  to  the  esophagus  the  elongated  infra-esophageal 


LOLIGO 


163 


ganglion,  which  is  supposed  to  represent  the  fused  pedal  and 
visceral  ganglia  and  (together  with  the  masses  that  connect 
the  supra-  and  infra-esophageal  ganglia  around  the  esoph- 
agus) the  pleural  ganglia. 

3.  The  anterior  prolongation  of  the  infra-esophageal  gang- 
lion to  form  the  propedal  portion,  which  supplies  nerves  to 

the  arms. 

4.  The  small  suprabuccal  ganglia,  lying  dorsal  to  the 
esophagus,  and  a  little  further  anterior  than  the  ends  of  the 
propedal  portion.  These  are  joined  by  connectives  with  the 
supra-esophageal  ganglia. 

5.  The  infrabuccal  ganglia,  about  the  same  size  as,  and 
lying  ventral  to,  the  suprabuccal  ganglia,  and  joined  with 
them  by  connectives  that  run  around  the  esophagus. 

Draw  a  figure  of  a  sagittal  section  of  the  head. 

Two  large  ganglia,  the  optic  ganglia,  lie  against  the  eyes 
and  will  be  seen  in  cross  sections  of  the  head  that  will  be 
studied  later.    A  dissection  of  one  side  of  the  head  will  show 

one. 

Open  the  animal  along  the  mid-dorsal  line  and  find  the  pen 
which  is  embedded  in  the  mantle.  After  exposing  it  for  its 
full  length,  turn  the  flaps  aside  and  see  that  it  lies  in  a  pocket. 
It  probably  represents  a  modified  shell  that  has  become  en- 
tirely inclosed  by  the  mantle.    What  is  its  function? 

Pull  the  pen  out  of  the  mantle  and  draw  it. 

With  a  razor  make  cross  sections  of  a  squid,  a  quarter  of 
an  inch  thick,  and  arrange  them  in  order,  in  a  little  water,  as 
they  are  made.  Identify  the  parts  you  have  found  in  dissec- 
tion. 

Make  drawings  of  the  sections  that  pass  through  the  infra- 
esophageal  ganglion,  through  the  eyes,  through  the  liver,  and 
through  the  heart. 

If  time  permits,  study  prepared  sections  that  have  pre- 
viously been  made.  The  structure  of  the  eye  and  the  posi- 
tions of  the  parts  of  the  nervous  system  should  receive  special 
attention. 


164  MOLLUSCA 

Specimens  of  other  cephalopods,  such  as  Octopus  and 
Nautilus,  should  be  compared  with  the  squid  and  the  adapta- 
tions that  fit  them  for  their  particular  lives  noted. 

Brooks:  The  Development  of  the  Squid  (Loligo  Pealii).  Mem.  Bost. 
Soc.  Nat.  Hist.,  1880. 

:    Handbook  of  Invertebrate  Zoology. 

Cowdry:    Color  Changes  in  Cephalopods.  Univ.  of  Toronto  Studies,  10, 

1911. 
Drew:    Sexual  Activities  of  the  Squid.     I.  Copulation,  Egg-laying  and 

Fertilization.     Jour.  Morph.,  22,  1911. 
:    Sexual   Activities   of   the   Squid.     II.   The   Spermatophore ;    Its 

Structure,  Ejaculation  and  Formation.     Jour.  Morph.,  32,  1919. 
Faussek:     Untersuchungen    iiber   die    Entwicklung    der   Cephalopoden. 

Mitt.  Zool.  Stat.  Neapel,  14,  1900. 
Griffin:    The  Anatomy  of  Nautilus  pompilius.     Mem.  Nat.  Acad.  Sci., 

9,  1900. 

Vialleton:  Recherches  sur  les  Premieres  Phases  Du  Developpement  de 
La  Seiche   (Sepia  officinalis).     Ann.  Sci.  Nat.   (7)  Zool.,  6,  1888. 

Willey:  Contribution  to  the  Natural  History  of  the  Pearly  Nautilus. 
Willey's  Zool.  Results.     4,  Cambridge  Univ.  Press,  1902. 

Williams:  The  Anatomy  of  the  Common  Squid,  Loligo  pealii.  Amer. 
Mus.  Nat.  Hist. 

:   The  Vascular  System  of  the  Common  Squid.    Am.  Nat.,  36,  1902. 


ARTHROPODA 

With  segmented  bodies  which  are  provided  with  segmented 
appendages. 

Class  1.  Crustacea. 

Usually  aquatic.  With  a  more  or  less  hardened 
outer  covering  and  many  thoracic  appendages. 
Subclass  1.  Branchiopoda. 

Crustacea  with  compound  eyes;  mandibular 
palp  usually  absent  or  vestigial;  4  or  more 
pairs  of  trunk  limbs  usually  broad  and  lobed. 
Some  orders  of  this  subclass  are:  Anostraca 
(Artemia) ;  Notostraca  (Apus) ;  Cladocera 
(Daphnia,  Simocephalus) . 

Subclass  2.  Ostracoda. 

Free  swimming  with  the  body  inclosed  in  a 
bivalve  shell;  mandibular  palp  usually  bira- 
mous;  not  more  than  2  pairs  of  trunk  limbs. 
(Cypris.) 

Subclass  3.  Copepoda. 

Free  or  parasitic;  no  compound  eyes  or  cara- 
pace; mandible  with  biramous,  uniramous  or 
no  palp;  typically  6  pairs  of  trunk  limbs,  first 
pair  uniramous,  next  4  pairs  biramous  and 
sixth  pair  often  uniramous.  (Cyclops,  Argu- 
lus,  Lernaea.) 

Subclass  4.  Cirripedia. 

Comparatively  large  and  usually  attached;  no 
compound  eyes  in  adult;  forms  that  are  not 
parasitic  covered  with  calcareous  plates;  usu- 
ally 6  pairs  biramous,  thoracic  limbs.  (Lepas, 
Balanus,  Chthamalus.) 

Subclass  5.  Malacostraca. 

Usually  of  considerable  size;  with  compound 
eyes,  usually  stalked;  mandibular  palp,  if 
present,  uniramous;  thorax  of  8  segments;  ab- 
domen typically  with  6  segments.  Some 
orders  of  this  large  subclass  are:  Leptostraca 
(Nebalia) ;  Hoplocarida  (or  Stomatopoda) 
(Chloridella) ;     Decapoda     (Homarus,     Cam- 

165 


166  ARTHROPOD A 

barus,   Crago,   Pagurus,   Emerita,    Callinectes, 
Cancer,  Uca) ;  Isopoda  (Idothea,  Erichsonella) ; 
Amphipoda     (Talorchestia,     Gammarus,     Ca- 
prella) . 
Class  2.  Arachnida. 

Body  divided  into  two  principal  regions,  ceph- 
alothorax  and  abdomen;  cephalothorax  bears 
sessile  eyes,  4  pairs  of  walking  legs,  chelicerae 
and  pedipalpi;  no  antennae;  respiration  usu- 
ally by  tracheae  or  lung  sacs.  Some  of  the 
important  orders  are:  Scorpionida  (Buthus) ; 
Xiphosura  (Limulus) ;  Pseudoscorpionida 
(Chelifer) ;  Pedipalpida  (Phrynus) ;  Solpugida 
(Galeodes) ;  Phalangida  (Phalangium) ;  Ara- 
neida  (Epeira,  Agalena) ;  Acarina  (Sarcoptes, 
Dermacentor) . 
Supplementary  to  the  Arachnida. 
Pycnogonida.     (Pantopoda.) 

(Doubtfully  referred  to  the  group.)  Body 
composed  of  segmented  cephalothorax  and 
vestigial  abdomen.  Legs  very  long,  angular, 
and  containing  portions  of  the  viscera.  No 
special  respiratory  organs  (Anoplodactylus, 
Pallene,  Phoxichilidium) . 

Class  3.  Onychophora. 

Elongated  bodies  with  some  annelid-like  char- 
acters. Appendages  short,  numerous,  and 
creased  rather  than  jointed.  Respiration  by 
means  of  tracheae.     (Peripatus.) 

Class  4.  Myriapoda. 

Generally  elongated  bodies  with  numerous 
jointed  appendages.  A  distinct  head  bearing 
ocelli,  antennae,  and  jaws  is  present.  Respir- 
ation by  means  of  tracheae. 

Order  1.  Symphyla. 

With  not  more  than  twelve  leg-bearing  trunk 
segments.  A  single  pair  of  branching  tracheae. 
(Scolopendrella.) 

Order  2.  Chilopoda. 

With  numerous  trunk  segments,  each  with  a 
single  pair  of  legs.  First  pair  of  trunk  appen- 
dages forming  poison  jaws.  Body  dorso- 
ventrally  compressed.     (Lithobius.) 


HOMARUS  167 

Order  3.  Diplopoda. 

With  numerous  trunk  segments,  each  with  two 
pairs  of  legs.  No  poison  jaws.  Body  not  com- 
pressed.    (Julus.) 

Order  4.  Pauropoda. 

With  ten  trunk  segments  and  nine  pairs  of  legs. 
(Pauropus.) 
Class  5.  Insecta. 

Body  divided  into  head,  thorax,  and  abdomen. 
Three  pairs  of  thoracic  legs  and  generally  one 
or  two  pairs  of  wings.  Some  of  the  important 
orders  are:  Thysanura,  Orthoptera,  Neurop- 
tera,  Hemiptera,  Diptera,  Lepidoptera,  Cole- 
optera  and  Hymenoptera. 

Brues  and  Melander:  Classification  of  Insects.  Bull.  Mus.  Comp.  Zool., 
73,  1932. 

Exner:  Die  Physiologie  der  facettierten  Augen  von  Krebsen  und  In- 
secten,  1891.    See  also  Biol.  Centr.,  11,  p.  581,  1891. 

Hilton:  The  Central  Nervous  System  of  Simple  Crustacea.  Jour. 
Comp.  Neur.,  v.  28,  No.  2,  1917. 

Prentiss:  The  Otocyst  of  Decapod  Crustacea:  Its  Structure,  Develop- 
ment, and  Functions.     Bull.  Mus.  Comp.  Zool.,   Harvard,  36,   1901. 

Watase:  On  the  Morphology  of  the  Compound  Eyes  of  Arthropods. 
Stud.  Biol.  Lab.  Johns  Hopkins  Univ.,  4. 

CRUSTACEA 

HOMARUS  AMERICANUS  (Lobster1) 

These  animals  are  not  generally  found  where  they  can  be 
readily  observed  in  nature,  but  many  valuable  observations 
can  be  made  on  specimens  confined  in  aquaria.  If  other 
animals  are  present  in  the  aquarium  notice  the  position  of 
defense  that  is  taken.  In  nature  the  animal  spends  consider- 
able time  under  rocks  with  the  anterior  end  of  the  body 
turned  toward  the  opening.  In  this  position  both  sense  organs 
and  weapons  are  in  the  proper  position  for  attack  or  defense. 
Notice  how  the  appendages  are  used.  Are  the  sense  organs 
moved  frequently?     What  is  the   advantage   of  having  the 

1  These  directions  may  be  used  for  the  crayfish  without  much  modifi- 
cation. The  smaller  size  of  these  animals  will  make  it  more  difficult 
to  trace  some  of  the  nerves  and  blood  vessels. 


168  ARTHROPODA 

eyes  on  stalks?  What  appendages  are  used  in  walking?  Are 
all  of  these  appendages  used  in  just  the  same  way?  Does 
the  animal  move  equally  well  in  all  directions?  Perhaps 
you  can  make  the  animal  swim;  if  so,  observe  the  method. 
Feed  a  specimen  with  portions  of  a  clam  or  fish,  and  see  how 
food  is  torn  to  pieces  and  transferred  to  the  mouth,  and  de- 
termine, if  possible,  how  the  mouth  appendages  are  used. 

Appendages  may  be  missing.  If  any  are,  notice  at  what 
point  they  are  broken.  Possibly  small  appendages  may  be 
growing  from  the  old  stubs.  Autotomy  may  be  studied  by 
crushing  a  claw  or  a  leg  of  the  fiddler  crab,  Uca.  Other 
forms  will  respond,  but  sometimes  not  promptly.  What  is 
the  importance  of  this  reaction? 

External  Anatomy. — As  in  Nereis,  the  body  is  segmented. 
The  five  segments  of  the  head  and  the  eight  segments  of  the 
thorax,  however,  are  immovably  fused  to  form  a  cephalo- 
thorax.  This  is  covered  dorsally  by  a  single  piece,  the  cara- 
pace. 

1.  Note,  on  the  carapace,  the  cervical  groove  between  the 
head  and  thorax,  and  the  beak  or  rostrum  forming  an  an- 
terior spine.  The  ventrolateral  edge  of  the  carapace  is  not 
attached.  A  flat  object  thrust  between  it  and  the  body 
passes  into  the  gill  chamber.  This  free  plate  of  the  carapace 
is  called  the  gill  cover.  Notice  the  hairlike  spines  along  its 
free  border.    What  purpose  do  these  serve? 

2.  The  abdomen  is  composed  of  seven  movable  segments, 
each  bearing  a  pair  of  jointed  appendages  except  the  last, 
which  is  sometimes  not  considered  a  true  segment  and  is 
called  the  telson.  Each  abdominal  segment  consists  of  a 
dorsal  piece,  the  tergum,  which  is  continued  as  a  free  plate 
laterally  (the  pleuron) ,  and  of  a  ventral  piece,  the  sternum. 
Move  the  abdominal  segments  and  see  where  they  are  hinged. 
How  are  the  terga  and  sterna  arranged  to  allow  free  move- 
ment? In  the  thorax  the  sterna,  though  fused,  can  be  dis- 
tinguished. 

3.  Appendages. — Aside  from  the  stalked  eyes,  whose  ho- 


HOMARUS  169 

mology  with  true  appendages  is  doubtful,  there  are  nineteen 
pairs.  These  are,  counting  from  before  backward:  anten- 
nules  (or  first  antennae),  antennae,  six  pairs  of  mouth  appen- 
dages, five  pairs  of  walking  legs  (pereiopods) ,  of  which  the 
first  are  the  claws  or  chelae,  and  six  pairs  of  swimmerets 
(pleopods) .  In  the  male,  the  first  two  pairs  of  pleopods  are 
modified  to  form  copulatory  organs.  The  first  pair  is  greatly 
modified  and  the  second  pair  bears  a  special  portion.1 

(a)  Turn  one  of  the  fifth  pair  of  pleopods  forward  and 
examine  its  posterior  aspect.  It  consists  of  a  basal  piece, 
the  protopod;  a  lateral  branch,  the  exopod;  and  a  median 
branch,  the  endopod.  This  branched  type  of  appendage  is 
designated  as  biramous.  What  is  its  use?  Compare  with 
this  the  modified  sixth  pair  of  pleopods,  called  the  uropods. 

Make  a  drawing  of  one  of  the  fifth  pleopods. 

(b)  In  front  of  the  chelae  will  be  seen  the  sixth  pair  of 
mouth  appendages,  the  third  maxillipeds.  Remove  that  of 
the  right  side  and  compare  it  with  the  fifth  pleopod.  In  ad- 
dition to  the  protopod,  exopod,  and  endopod,  it  bears  a  long 
blade,  the  epipod,  which  extends  into  the  gill  chamber.  The 
protopod  is  composed  of  two  segments,  coxopod  and  basipod; 
the  endopod  of  five  segments,  ischipod,  meropod,  carpopod, 
propod,  and  dactylopod.  The  exopod  is  composed  of  one 
long  and  many  short  segments.  How  is  the  appendage 
modified  to  serve  in  feeding? 

Make  a  drawing  of  the  third  maxilliped. 

(c)  Remove  the  remaining  five  mouth  appendages  and 
compare  each  with  the  third  maxilliped.  These  are,  begin- 
ning posteriorly,  the  second  maxilliped,  first  maxilliped,  sec- 
ond maxilla  (with  a  broad  paddle,  the  scaphognathite,  the 
use  of  which  should  be  understood),  first  maxilla,  and  the 
mandible.  Just  back  of  the  mandibles  are  two  small  flaps, 
the  paragnatha,  which  are  not  true  appendages.  Do  you 
understand  the  use  of  each  of  these  appendages?  Most  of 
the  appendages  have  parts  that  may  be  compared  with  the 

1The  crayfish  has  the  first  two  pairs,  both  greatly  modified. 


170  ARTHROPODA 

typical  biramous  appendage,  but  they  are  much  modified  to 
serve  special  functions,  and  the  exact  homologies  are  not  im- 
portant. Between  the  mandibles  note  the  mouth,  bounded  in 
front  by  the  labrum. 

Drawings  of  these  appendages  may  be  made  if  time  per- 
mits. 

(d)  The  second  antennae  are  biramous.  Notice  on  the 
ventral  side  of  the  basal  joint  of  an  antenna  the  opening  of 
the  green  gland  or  nephridium. 

(e)  The  first  antennae,  though  branched,  are  not  con- 
sidered to  be  of  the  biramous  type.  Do  you  know  why? 
Remove  one  and  note  on  the  dorsal  surface  of  the  basal  joint 
a  groove  at  whose  median  extremity  is  a  small  hole,  the 
opening  into  the  statocyst.  Do  you  know  the  probable  func- 
tion of  the  antennules  and  of  the  statocyst?  What  reason 
is  there  for  having  both  first  and  second  antennae? 

(/)  Compare  the  pereiopods  with  the  third  maxilliped. 
Which  is  lacking,  endopod  or  exopod?  Examine  each  of  the 
joints  of  one  of  these  appendages  and  see  in  what  directions 
the  appendage  may  be  moved.  Are  there  any  ball-and- 
socket  joints?  Compare  the  chelae  with  the  other  pereiopods 
and  see  how  they  differ.  To  what  part  of  a  chela  does  the 
last  segment  of  the  last  pereiopod  correspond?  What  reason 
is  there  for  having  these  appendages  different?  Do  you 
think  the  arrangement  of  the  appendages  would  aid  the  lob- 
ster in  climbing  over  rough  bottom? 

Open  one  of  the  large  chelae  and  determine  how  the 
muscles  are  arranged  to  control  its  opening  and  closing. 
Which  muscles  are  strongest?  Find  how  the  muscles  are  at- 
tached to  the  "thumb." 

Find  the  openings  of  the  sexual  ducts  on  the  basal  joints 
of  the  pereipods;  the  fifth  pair  in  the  male,  the  third  pair 
in  the  female.  In  the  female  there  is  an  opening  into  a 
seminal  receptacle  through  a  triangular  elevation  on  the  ven- 
tral side  of  the  thorax. 

4.  Gills. — Remove  the  gill  cover  of  the  left  side,  being 


HOMARUS  171 

careful  not  to  injure  the  gills.  Extending  up  into  the  gill 
cavity  are  seven  epipods  belonging  to  the  three  maxillipeds 
and  the  four  anterior  pereiopods.  They  separate  the  gills 
into  groups.  Each  group  will  be  seen  to  correspond  to  a 
segment.  The  gills  show  three  sorts  of  attachments:  (a)  to 
the  appendages  themselves  (podobranchs) ,  {b)  to  the  articu- 
lar membranes  between  appendages  and  body  wall  {arthro- 
branchs),  and  (c)  to  the  body  wall  itself  {pleurobranchs) . 
There  are  two  arthrobranchs  in  some  segments,  one  behind 
and  above  the  other.  How  is  the  current  of  water  forced 
through  the  gill  chamber?  What  is  the  function  of  the  epi- 
pods? What  direction  must  the  water  take  through  the  gill 
chamber?  Examine  the  structure  of  a  gill.  Move  one  of  the 
appendages  to  which  a  gill  is  attached  and  see  the  effect  on 

the  gill.1 

Internal  Anatomy. — Remove  the  carapace  (beginning  at 
the  middle  of  the  posterior  margin  and  cutting  forward,  hold- 
ing the  cartilage  knife  parallel  with  the  surface)  as  far 
laterally  as  the  upper  limits  of  the  gill  chambers  and  an- 
teriorly to  the  base  of  the  rostrum.  What  is  the  pigmented 
membrane  for?  Dissect  it  off  so  underlying  organs  may  be 
seen. 

1.  The  chitinous  stomach  lies  near  the  anterior  end  with 
the  ophthalmic  artery  running  along  its  mid-dorsal  line.  Be- 
side and  behind  the  stomach  are  two  masses  of  muscle  which 
you  have  severed  from  the  carapace.  These  are  the  man- 
dibular muscles,  and  each  is  divided  into  an  anterior  and  a 
posterior  bundle.  Lateral  to  these  muscle  masses  are  the 
yellow-green  digestive  glands,  commonly  called  liver.  Be- 
tween and  in  front  of  the  posterior  mandibular  bundle  note 
the  gonads,  and  follow  one  forward  by  pressing  aside  the 
muscle  mass.  In  the  male  the  testis  is  a  slender,  white,  con- 
voluted cord,  which  ends  blindly  against  the  side  of  the 
stomach.  The  extent  and  position  of  the  far  thicker  yellow 
ovary  is  much  the  same  (unless  the  animal  be  mature,  in 
which  case  it  will  be  found  greatly  enlarged  and  orange). 

1The  crayfish  differs  slightly  in  gill  arrangement. 


172  ARTHROPODA 

2.  The  heart  extends  through  the  posterior  third  of  the 
thorax.  Remove  the  upper  part  of  the  delicate  'pericardium 
surrounding  it,  cut  its  arterial  and  other  connections,  and 
place  it  in  water.  Note  the  shape,  the  origin  of  the  arteries, 
and  the  three  pairs  of  ostia.  Do  you  understand  how  the 
heart  receives  blood? 

3.  Trace  the  gonads  as  far  as  the  abdomen,  noting  the 
single  anastomosis  between  those  of  opposite  sides  just  in 
front  of  the  heart.  Beneath  the  heart  the  sexual  ducts  are 
given  off — vasa  deferentia  in  the  male,  oviducts  in  the  fe- 
male. Trace  one  outward  and  downward  to  its  opening  by 
removing  a  portion  of  the  body  wall  and  of  the  basal  joint 
of  the  proper  leg. 

4.  Remove  the  posterior  lateral  body  wall  forward  to  a 
position  opposite  the  anterior  third  of  the  stomach.  Pull  the 
anterior  lobe  of  the  liver,  which  extends  beneath  the  stomach, 
outward  and  backward.  The  liver  will  be  seen  to  be  at- 
tached to  the  pyloric  end  of  the  stomach  (i.  e.,  the  smaller 
part,  where  the  stomach  passes  into  the  intestine).  Cut  this 
attachment  and  note  that  it  is  really  where  the  liver  opens 
into  the  stomach.  Just  back  of  this  point  the  right  and  left 
lobes  of  the  liver  are  connected  by  a  cross  branch  passing 
beneath  the  intestine.  Remove  one  liver  lobe  back  to  the 
abdomen.  After  having  the  circumesophageal  connectives 
pointed  out,  remove  the  stomach  by  cutting  the  esophagus, 
the  intestine,  and  the  bands  of  muscles  attached  to  the 
stomach.  Examine  it  in  water,  noting  the  cardiac  and 
pyloric  parts,  the  chitinous  grinding  and  straining  apparatus 
in  the  interior,  and  the  muscles  and  plates  that  cause  the 
movements  of  the  grinding  apparatus.  Why  does  a  lobster 
with  chelae  and  six  pairs  of  mouth  appendages  need  a  gastric 
mill? 

5.  Between  the  circumesophageal  connectives  medially 
and  the  large  antennary  muscles  laterally,  note  the  oval  ex- 
cretory organs,  called  the  green  glands.  They  are  covered 
by  a  very  delicate  membrane.    Poke  a  small  hole  in  one  of 


HOMARUS  173 

the  membranes  and  with  a  blowpipe  show  that  it  is  really  a 
thin  bladder.  Its  opening  on  the  antenna  has  already  been 
seen. 

6.  Remove  the  dorsal  wall  of  the  abdomen  and  trace  the 
posterior  portions  of  the  gonads,  liver  lobes,  and  intestine. 
In  the  sixth  abdominal  segment  the  intestine  swells  to  form 
the  chitin-lined  rectum  and  gives  off  the  blind  intestinal 
caecum. 

Circulatory  and  Nervous  Systems.1 — Remove  the  cara- 
pace of  an  injected  specimen  as  before,  also  the  gill  cover  and 
gills  on  one  side. 

1.  There  can  generally  be  seen,  through  the  transparent 
body  wall,  efferent  branchial  veins,  which  return  the  blood 
from  the  gills.  These  unite  into  six  large  ones  which  open 
into  the  pericardium  at  the  side.  Find  these  openings  if  pos- 
sible.   Do  you  understand  how  blood  gets  into  the  heart? 

2.  Note,  at  the  anterior  end  of  the  heart,  the  ophthalmic 
artery  and  the  two  antennary  arteries.  Trace  the  former 
forward  to  the  rostrum,  cut  it  on  the  stomach  and  turn  it 
forward  for  future  study.  Trace  the  antennary  arteries  to 
the  mandibular  muscles  and  cut  them  near  the  heart.  Press 
the  front  end  of  the  heart  back  and  note  the  two  small 
hepatic  arteries.  Each  branches  immediately,  one  division 
passing  between  the  gonads,  and  the  other  laterally. 

3.  Remove  the  muscles  on  one  side  of  the  heart  and  ex- 
amine it  from  the  side,  noting  the  great  sternal  artery  ex- 
tending downward,  and  the  smaller  dorsal  abdominal  artery 
running  back  above  the  intestine.  Follow  the  latter  through 
the  abdomen. 

4.  Cut  all  arteries  and  remove  the  heart.    Trace  the  an- 


1The  circulatory  system  of  a  fresh  specimen  may  be  satisfactorily 
injected  with  starch  mass  by  inserting  the  needle  of  a  hypodermic 
syringe  into  the  pericardium  from  the  posterior  margin  of  the  carapace. 
The  operation  is  easily  performed  when  the  distance  to  the  pericardium 
is  understood.  The  carapace  may  be  cut  away  and  the  needle  inserted 
directly  into  the  heart  if  preferred. 


174  ARTHROPODA 

tennaries  through  the  mandibular  muscles,  noting  the  branch 
to  the  stomach. 

5.  Remove  the  thoracic  viscera  as  before,  follow  the  cir- 
cumesophageal  connectives  forward  and  identify  the  cerebral 
ganglia  in  order  not  to  destroy  them. 

6.  Follow  one  antennary  artery  to  the  green  gland,  an- 
tennary  muscle,  eye  muscle,  etc. 

7.  Follow  the  distribution  of  the  ophthalmic  artery. 

8.  Remove  the  intestine  and  muscles  of  the  abdomen,  and 
find  and  trace  forward  the  ventral  nerve  chain.  Notice  the 
position  of  the  ganglia  and  the  nerves  that  leave  them  and 
the  connectives.  In  the  thorax  the  ventral  nerve  chain  passes 
beneath  a  system  of  chitinous  plates  {the  endophragmal 
skeleton)  and  lies  in  a  cavity,  the  ventral  blood  sinus.  Note 
the  enlarged  subesophageal  ganglion,  the  cross  commissure 
just  back  of  the  esophagus,  the  nerves  to  the  mouth  ap- 
pendages, nerves  from  the  cerebral  ganglia,  and  nerves  from 
the  other  ganglia.  What  indication  is  there  that  the  sub- 
esophageal ganglia  represent  more  than  a  single  pair? 

Draw  the  nervous  system. 

9.  The  sternal  artery  passes  through  the  ventral  nerve 
chain  and  then  extends  backward  and  forward  as  the  ventral 
longitudinal  artery.  Remove  the  nervous  system  and  follow 
this  artery. 

Draw  a  diagrammatic  cross  section  through  the  thorax, 
putting  in  one  drawing  the  circulation  from  the  heart  through 
the  sternal  artery  to  the  limbs  and  back  through  the  gills  to 
the  heart. 

Andrews:    The  Keeping  and  Rearing  of  Crayfish  for  Class  Use.    Nat. 
Stud.  Rev.,  2,  1906. 

:    The  Young  of  the  Crayfishes  Astacus  and   Cambarus.     Smith- 
sonian Cont.  to  Knowl.,  35,  1907. 

Conjugation  in  the  American  Crayfish.    Am.  Nat.,  29,  1895. 


Bumpus:    Movements  of  Certain  Lobsters  Liberated  at  Woods  Hole. 

Bull.  U.  S.  Com.  Fish.,  1899. 

:     Embryology   of  the   American   Lobster.    Jour.   Morph.,  5,   1891. 

Herrick:    Natural  History  of  the  American  Lobster.     Bull.  U.  S.  Bur. 

Fish.,  29,  1909. 


HOMARUS,    CALLINECTES  175 

Huxley:   The  Crayfish.    An  Introduction  to  the  Study  of  Zoology.    1884. 

Mead:  Habits  and  Growth  of  Young  Lobsters.  Rhode  Island  Com. 
Inland  Fisheries,  21,  1901. 

Paul:     Reflexes   of   Autotomy.     Proc.   Roy.   Soc.   Edinburgh,  35,   1915. 

Pearl  and  Clawson:  Variation  and  Correlation  in  the  Crayfish.  Car- 
negie Inst.  Pub.,  64,  1907. 

Pearse:  Observations  on  Copulation  Among  Crawfishes  with  Special 
Reference  to  Sex  Recognition.    Am.  Nat.,  43,  1909. 

Steele:  Regeneration  of  Crayfish  Appendages.  Univ.  Missouri  Studies, 
2,  1904. 

:    Regeneration  in  Compound  Eyes  of  Crustacea.    Jour.  Exp.  Zool., 

5,  1907. 

Williams:  The  Stomach  of  the  Lobster  and  the  Food  of  Larval  Lob- 
sters.   An.  Rep.  Com.  Inland  Fish.,  Rhode  Island,  37,  1907. 

Wood  and  WTood:  Mechanism  of  Autotomy  in  Decapod  Crustaceans. 
Jour.  Exp.  Zool.,  62,  1932. 

CALLINECTES  SAPIDUS  (Blue  Crab) 

Crabs  may  be  found  in  shallow  water  along  shore,  where 
they  may  be  easily  observed  on  quiet  days.  In  what  direc- 
tion does  the  animal  normally  move?  How  are  the  legs 
used?  What  is  the  attitude  of  defense?  Determine  how  the 
blue  crab  swims.  What  do  crabs  apparently  use  for  food? 
Do  they  conceal  themselves,  are  they  protectively  colored, 
or  do  they  depend  entirely  upon  their  weapons  for  defense? 

In  studying  the  anatomy  of  the  crab,  constant  compari- 
sons should  be  made  with  the  lobster. 

External  Anatomy. — 1.  The  body  is  composed  of  cephalo- 
thorax  and  abdomen.  Dorsally  note  the  shape  of  the  cara- 
pace and  the  position  of  the  abdomen.  The  size  of  the 
abdomen  differs  in  male  and  female.  To  what  use  is  the 
larger  abdomen  of  the  female  adapted? 

2.  Note  the  first  antennae,  second  antennae,  and  eyes,  and 
see  how  they  are  packed  away  in  recesses  in  the  carapace. 
In  the  living  animal  see  if  any  of  these  are  frequently  moved. 

3.  The  third  maxillipeds  are  flattened  and  cover  the  other 
mouth  appendages. 

4.  Straighten  the  abdomen  and  note  the  anus.  Compare 
the  abdomen  of  a  male  with  that  of  a  female  and  both  with 
that  of  the   lobster.     The   dorsal   side   of  each   segment  is 


176  ARTHROPOD A 

covered  by  a  tergum.  The  covering  between  each  pair  of 
pleopods  is  the  sternum,  the  immovable  flap  lateral  to  them 
is  the  pleuron.  Compare  the  abdominal  appendages  or  pleo- 
pods of  a  male  and  a  female. 

5.  The  ventral  side  of  the  cephalothorax  is  covered  by 
the  sternal  plastron.  Note  the  eight  sterna  and  six  pairs  of 
lateral  episterna,  the  anterior  pair  of  which  is  very  small. 

6.  In  the  female  find  the  openings  of  the  oviducts  in  the 
sixth  sternum. 

Make  a  drawing  of  the  ventral  side. 

7.  Expose  the  gill  chamber  and  compare  the  gill  distri- 
bution with  that  of  the  lobster. 

8.  Remove  the  left  third  maxilliped  entire,  and  compare 
it  with  the  same  appendage  of  a  lobster.  The  protopod  is 
composed  of  two  segments  (coxopod  and  basipod).  The 
endopod  has  five  pieces  {ischipod,  meropod,  carpopod,  pro- 
pod,  and  dactylopod).  The  exopod  has  two  large  and  many 
small  segments.  Attached  to  the  coxopod  laterally  is  an  epi- 
pod  which  extends  into  the  gill  chamber. 

9.  Remove  the  remaining  mouth  appendages  on  the  left 
side  and  compare  them  with  the  third  maxilliped.  They  are: 
second  maxilliped  bearing  epipod  and  two  small  gills;  first 
maxilliped  with  an  epipod;  second  maxilla  with  a  flattened 
exopod,  called  the  scaphognathite,  which  is  made  up  of  both 
exopod  and  epipod  and  which  has  a  special  function  that 
should  be  understood;  first  maxilla,  thin  and  leaflike;  man- 
dible with  two  hard  rods  for  the  attachment  of  muscles. 

10.  Detach  and  examine  one  each  of  the  eyes  and  first 
and  second  antennae.  On  the  flat  side  of  the  basal  joint  of 
each  first  antenna  note  a  dark  suture — the.  scar  of  the  former 
opening  into  the  statocyst.  Do  you  understand  what  function 
is  performed  by  the  statocysts?  Near  the  base  of  the  second 
antenna  find  the  opening  of  the  renal  organ  (green  gland). 

11.  Compare  each  of  the  five  walking  legs  (pereiopods) 
with  the  third  maxilliped.  What  part,  endopod  or  exopod, 
is  lacking?     Which  bears   forceps  or  chelae?     Note  in  the 


CALLINECTES  177 

male  the  openings  of  the  sperm  ducts  on  the  coxopods  of  the 
fifth  pair. 

Internal  Anatomy. — Remove  the  entire  dorsal  part  of  the 
carapace. 

X.  Posterolateral^  are  two  firm  prominences,  the  flanks, 
containing  muscles.  What  are  these  muscles  for?  Anterior 
to  these  are  the  gill  chambers  covered  by  a  thin  cuticle.  Re- 
move this  and  note  the  gills  with  their  tips  converging 
medially. 

2.  Between  the  gill  chambers  and  flanks  is  the  delicate 
pericardium.  Remove  this  and  find  the  heart  with  its  ostia. 
Anteriorly  it  sends  out  an  ophthalmic  artery  and  two  an- 
tennary  arteries.  Just  anterior  to  the  heart  are  muscles 
which  were  attached  to  the  shell.  What  organs  do  they  sup- 
ply? The  antennary  arteries  pass  through  the  heads  of  a 
pair  of  the  muscles. 

3.  In  front  of  the  gill  chambers  are  the  gonads.  In  the 
female  the  orange  ovary  will  be  seen  lying  on  the  yellow 
liver.  In  the  male  the  slender,  wavy,  white  cord,  the  testis, 
lies  in  approximately  the  same  position. 

4.  The  heart  is  attached  to  the  pericardium  by  muscular 
strands.  Cut  these,  and  the  three  anterior  arteries,  and  re- 
move the  heart,  noting  the  two  hepatic  arteries  beneath  the 
antennary  arteries,  the  great  sternal  artery  passing  down- 
ward from  the  under  side,  and  the  small  abdominal  artery 
just  behind  the  last. 

Draw  dorsal  and  ventral  views  of  the  heart  to  show  the 
ostia  and  the  origins  of  arteries. 

5.  Cut  across  a  gill  and  notice  its  afferent  and  efferent 
vessels.  The  latter  is  continuous  with  one  of  the  sinuses 
which  empty  into  the  pericardial  cavity.  Can  you  determine 
how  many  sinuses  there  are?  Do  you  understand  how  the 
heart  receives  blood? 

Reproductive  System. — Beginning  anterolateral^,  on  one 
side,  dissect  out  the  reproductive  organs,  noting  at  the  same 
time  the  distribution  of  arteries. 
12 


178  ARTHROPODA 

(a)  Female  Reproductive  Organs.1 — Each  ovary  passes 
inward  and  backward,  anastomoses  with  the  one  of  the  other 
side  behind  the  stomach,  and  extends  back  to  the  abdomen. 
On  a  level  with  the  posterior  part  of  the  stomach  a  branch 
passes  downward  and  outward  and  is  continuous  with  a 
dense,  white  organ,  the  seminal  receptacle.  Leave  this  re- 
ceptacle in  place,  but  remove  the  entire  ovary. 

(£>)  Male  Reproductive  Organs. — The  usually  slender  tes- 
tis which  is  large  during  the  season  of  activity  passes  inward 
and  backward,  anastomoses  with  its  fellow  of  the  other  side 
behind  the  stomach,  and  is  continued  as  a  thick,  much-coiled 
tube,  the  vas  deferens,  to  the  median  side  of  the  flank.  It 
then  runs  forward  nearly  to  the  stomach,  turns  back  again, 
and  enters  the  substance  of  the  flank.  By  removing  the  top 
of  the  flank  and  the  upper  side  of  the  coxopod  of  the  swim- 
ming leg,  it  can  be  followed  to  its  external  opening. 

Digestive  System. — 1.  The  liver  is  large  and  fills  a  large 
part  of  the  body  cavity.  Remove  the  portion  of  it  that  is  in 
the  region  of,  and  anterior  to,  the  stomach,  noting  its  con- 
nection with  the  alimentary  tract. 

2.  The  stomach  is  a  chitinous  box  divided  into  a  larger 
cardiac  and  a  smaller  pyloric  portion.  On  each  side  find  the 
duct  from  the  liver,  and  a  slender,  white,  coiled  tube,  the 
pyloric  caecum. 

3.  Follow  the  delicate  intestine  back  beneath  the  heart. 
Between  the  posterior  edges  of  the  flank  is  a  white  mass  com- 
posed of  a  coiled  tube,  the  intestinal  caecum.  Remove  the 
terga  of  the  abdominal  segments,  follow  this  caecum  to  its 
connection  with  the  intestine,  and  follow  the  latter  to  the 
anus,  noting  its  chitinous  lining. 

4.  Cut  out  the  alimentary  tract,  open  the  stomach,  and 
examine  the  grinding  and  straining  apparatus. 

Make  a  drawing  of  the  alimentary  canal. 
Excretory  Organs. — Examine  the  antennary  gland  (green 
gland)  on  the  inside  of  the  carapace  opposite  the  base  of  the 
1The  specimen  must  be  large  and  mature. 


CALLINECTES,    PAGURUS  179 

antenna.  It  consists  of  a  thin  bladder,  and,  anterior  to  this, 
a  mass  composed  of  a  coiled  tube  which  opens  at  the  base  of 
the  second  antenna. 

Nervous  System. — Find  the  ring  of  ganglia  around  the 
ventral  end  of  the  sternal  artery.1  Trace  the  nerves  from 
this  to  the  appendages  and  to  the  small  abdomen.  Trace  the 
circumesophageal  connectives  around  the  gullet  (they  an- 
astomose just  behind  it)  to  the  cerebral  ganglia.  Along  with 
the  distribution  of  the  ophthalmic  and  antennary  arteries, 
trace  the  nerves  from  the  cerebral  ganglia  to  the  eyes,  an- 
tennae, etc.  Why  should  the  nervous  system  be  more  con- 
centrated than  it  is  in  the  lobster? 

Make  a  drawing  of  the  nervous  system. 

Brooks:    Hand-book  of  Invertebrate  Zoology. 

Churchill:    Life  History  of  Blue  Crab.    Bull.  U.  S.  Bur.  Fish.,  vol.  36, 

1919. 

Gurney:    Metamorphosis  of  Corystes.    Quart.  Jour.  Mic.  Sci.,  46,  1902. 
Hay:    Life  History  of  the  Blue  Crab.    Rep.  U.  S.  Bur.  Fish.,  1912. 

PAGURUS  (Hermit  Crab) 

Examine  a  living  specimen  and  see  how  it  moves,  and 
how  the  aperture  of  the  shell  is  closed  by  the  two  large  claws 
when  the  animal  withdraws. 

With  a  hammer  crack  the  shell  away  from  the  animal  and 
examine  the  twisted  abdomen. 

1.  Has  it  lost  its  symmetry  in  appendages  as  well  as  in 
shape? 

2.  How  many  of  the  appendages  have  been  retained? 
What  is  the  function  of  these  appendages? 

3.  Remove  several  other  specimens  from  their  shells  and 
place  them  in  a  dish  of  sea  water  together.  Do  they  seem 
disturbed?     Compare  their  actions  with  those  in  shells. 

4.  Place  an  empty  shell  in  the  dish  and  see  what  happens. 

5.  Put  more  empty  shells  in  the  dish,  but  be  sure  they 
are  not  quite  large  enough  for  the  crabs.     Then  add  some 

xIn  a  fresh  specimen  the  ganglia  can  be  more  easily  studied  after 
treating  them  with  strong  alcohol  or  Schaudinn's  fluid  for  a  moment. 


180  ARTHROPODA 

larger  shells  and  watch  the  crabs  test  them  to  determine 
which  will  serve  best. 
A  drawing  is  desirable. 

Thompson:    The  Metamorphoses  of  the  Hermit  Crab.    Proc.  Bost.  Soc. 
Nat.  Hist.,  31,  1903. 

EMERITA  (Sand  Mole) 

On  sand  beaches,  between  low-  and  high-water  mark, 
there  may  frequently  be  seen  the  shallow  depressions  that 
mark  the  places  where  these  animals  have  burrowed.  They 
may  be  dug  out  with  a  shovel,  but  they  quickly  disappear 
again. 

1.  Notice  their  shape  and  the  ease  and  rapidity  with 
which  they  burrow. 

2.  Place  specimens  in  a  dish  containing  sand  and  a  little 
sea  water  and  try  to  determine  just  how  the  burrowing  is 
done.  This  may  frequently  be  done  by  holding  a  specimen 
so  it  just  touches  the  sand.  Which  end  goes  into  the  sand  first? 
Notice  the  positions  in  which  the  appendages  are  held.  Does 
this  have  anything  to  do  with  the  direction  in  which  it  bur- 
rows? Does  the  animal  jump  or  crawl?  In  what  direction 
and  how  can  it  swim? 

3.  Examine  the  body  and  see  if  it  is  divided  into  head, 
thorax,  and  abdomen.  In  what  way  is  the  shape  of  the  telson 
adapted  to  its  function? 

4.  Examine  the  appendages. 

(a)  The  stalked  eyes. 

(b)  The  biramous  first  antennae  and  the  exceedingly  long, 
feathery  second  antennae.  What  is  the  usual  position  of  the 
antennae? 

(c)  The  mouth  appendages.  Are  strong,  hard  mandibles 
present?    What  must  the  character  of  the  food  be? 

(d)  The  thoracic  appendages.  How  many  are  there? 
Are  they  similar?    Are  there  any  chelae? 

(e)  The  abdominal  appendages.  Are  they  all  alike? 
What  functions  are  performed  by  them? 

Make  a  drawing. 


EMERITA,    CHLORIDELLA  181 

CHLORIDELLA 

Compare  the  animal  carefully  with  the  lobster,  noting  all 
of  the  important  differences.  The  posterior  three  thoracic 
segments  are  free.  The  male  possesses  a  copulatory  organ 
on  the  basal  joint  of  the  last  thoracic  leg.  In  the  female 
the  opening  of  the  oviducts  is  in  the  midventral  line,  on  the 
next  to  the  last  thoracic  segment.  Examine  the  chelae  and 
compare  them  with  the  chelae  of  a  lobster.  Are  they  ho- 
mologous appendages  in  the  two  animals?  If  you  have  liv- 
ing specimens,  study  their  movements  while  they  are  walking 
and  swimming. 

A  drawing  of  a  side  or  ventral  view  will  be  profitable. 

Internal  Anatomy. — 1.  Remove  the  top  of  the  carapace 
and  abdomen.  Beneath  the  muscles  note  the  elongated,  white 
tube,  the  heart,  which  extends  from  the  stomach  to  the  fifth 
abdominal  segment.  The  anterior  end  is  slightly  enlarged 
and  gives  rise  to  the  anterior  aorta.  The  posterior  end  gives 
rise  to  a  posterior  aorta.  Note  lateral  arteries  and  ostia. 
Remove  the  heart. 

2.  Beneath  the  heart,  in  the  male,  is  a  whitish,  pigmented, 
flattened  mass  which  consists  of  two  convoluted  tubes,  the 
testes.  Cut  this  mass  across  between  the  second  and  third 
abdominal  segments  and  force  it  posteriorly.  The  two  testes 
are  continuous  posteriorly.  Follow  them  anteriorly  and  find 
the  slender,  dense,  coiled  vasa  deferentia  passing  outward 
and  downward  at  the  posterior  end  of  the  third  thoracic  seg- 
ment. Cut  them  and  lay  them  back  where  they  can  be  dis- 
sected later.  The  testes  extend  forward  to  the  region  of  the 
stomach.    Remove  the  testes. 

3.  Beneath  the  heart,  in  the  female,  are  the  two  ovaries. 
Trace  them  forward  and  backward,  and  find  the  very  slender 
oviduct  that  extends  from  each  outward  and  downward  in 
the  region  of  the  antepenultimate  thoracic  segment.  Remove 
the  ovaries,  deferring  the  tracing  of  the  oviduct. 

4.  Beneath  the  reproductive  organs  is  the  granular  liver. 
This  consists  of  two  lobes  which  extend  from  the  stomach  to 


182  ARTHROPODA 

the  end  of  the  telson.  They  form  saccular  diverticula  be- 
tween segments  and  in  the  telson.  Where  do  they  open  into 
the  alimentary  tract? 

5.  Free  the  intestine,  which  is  between  the  lobes  of  the 
liver.    The  rectum  is  in  the  sixth  abdominal  segment. 

6.  Pull  back  the  anterior  end  of  the  stomach,  identify  the 
circumesophageal  connectives,  in  order  not  to  destroy  them, 
and  free  the  stomach  by  cutting  the  esophagus  and  intestine. 
Examine  the  stomach  under  water. 

7.  Trace  the  nerve  chain.  What  ventral  ganglia  are 
fused?  The  cerebral  ganglia  are  most  easily  exposed  by  slic- 
ing away,  very  superficially,  the  dorsal  surface  of  the  rostrum 
and  pressing  the  eye  muscles  apart. 

A  drawing  of  the  nervous  system  will  be  profitable. 

8.  Trace  the  genital  ducts  to  their  external  openings. 

MICHTHEIMYSIS  (OR  HETEROMYSIS) 

If  living  specimens  are  to  be  had,  watch  them  swim,  and 
determine  what  parts  are  used  in  swimming.  Does  the  ani- 
mal swim  in  one  direction  or  in  both? 

1.  Compare  the  body  with  that  of  a  lobster. 

2.  Are  appendages  present  on  each  of  the  divisions  of  the 
body?  Compare  them  with  the  appendages  of  the  lobster? 
How  do  the  thoracic  appendages  differ? 

3.  Notice  the  statocysts  in  the  tail  fin. 

4.  The  living  animal  is  transparent,  and  many  internal 
organs,  such  as  heart,  gills,  and  portions  of  the  alimentary 
canal,  can  be  seen. 

//  time  permits,  make  a  drawing. 

Bergh:    Beitriige  zur  Embryologie  der  Crustacea.    Zool.  Jahrb.  (Anat.), 
6,  1893 

TALORCHESTIA  (Beach-flea) 

These  active  little  animals  inhabit  sand  beaches,  where 
they  burrow  in  the  sand  near  high-water  mark.  Turn  over 
some  of  this  sand  and  notice  the  activity  of  the  animals  that 
are   disturbed.      (In    the    decaying   vegetable    matter   which 


MICHTHEIMYSIS,   TALORCHESTIA  183 

accumulates  along  such  beaches  along  high-water  mark, 
smaller  animals  of  a  closely  related  genus,  Orchestia,  may  be 
found.  The  movements  of  both  species  are  much  the  same.) 
How  far  can  a  specimen  leap?  Are  the  leaps  of  an  individual 
continuously  in  one  direction,  so  it  may  get  away  from  the 
point  of  danger?  Is  each  leap  straight  forward  or  does  the 
animal  whirl  in  the  air?  What  purpose  may  be  served  by  the 
leaping?  Try  to  catch  a  specimen.  Determine  how  the  leap- 
ing is  accomplished.    Determine  how  the  specimens  burrow. 

If  you  will  walk  along  a  beach  some  quiet  night  with  a 
lantern  you  will  probably  see  something  of  the  night  activi- 
ties of  these  animals. 

1.  Select  a  large  specimen  and  count  the  number  of  seg- 
ments.   Is  the  body  divisible  into  head,  thorax,  and  abdomen? 

2.  The  eyes  are  not  stalked.    Are  they  compound? 

3.  The  second  antennae  of  the  male  are  very  large.  Com- 
pare them  with  the  first  antennae  and  with  the  antennae  of  a 
female. 

4.  Around  the  mouth  are  the  labrum,  forming  an  upper 
lip,  the  first  maxillipeds  (fused) ,  forming  a  lower  lip,  and 
between  them  the  mandibles,  first  maxillae,  and  second 
maxillae. 

5.  Examine  the  appendages  behind  the  mouth.  How 
many  are  there?  How  many  bear  claws?  Compare  these 
claws  with  those  of  a  lobster,  and  see  how  they  differ.  Which 
appendages  are  used  in  crawling?  Some  of  the  appendages 
are  arranged  so  they  can  be  twisted  around  by  the  sides  of 
the  animal.  What  is  their  function?  What  are  the  remain- 
ing appendages  used  for? 

6.  Spread  the  appendages  apart  and  find  the  gills,  which 
are  attached  to  the  bases  of  the  appendages. 

Make  a  drawing  of  the  animal. 

Kunkel:    The  Arthrostraca  of  Connecticut.  Conn.  State  Geol.  and  Nat. 

Hist.  Survey,  Bull.  26,  1918. 
Smallwood:    The  Beach  Flea:    Talorchestia  longicomis.     Cold  Spring 

Harbor  Monogr.,  1,  1903. 


184  ARTHROPODA 

PORCELLIO  OR  ONISCUS  (Sow-bug) 

These  animals  occur  in  damp  places,  such  as  under  stones, 
logs,  etc.,  and  in  cellars.  They  live  for  the  most  part  on  de- 
caying vegetable  matter.  To  what  class  of  the  Arthropoda 
do  they  belong? 

1.  Notice  the  shape.    Is  this  an  adaptation? 

2.  Is  the  body  divisible  into  head,  thorax,  and  abdomen? 
Count  the  number  of  segments.  Is  there  any  evidence  of 
fusion  at  the  posterior  end  of  the  body? 

3.  Examine  the  appendages. 

(a)  Are  the  eyes  stalked  or  sessile? 

(6)  Only  one  pair  of  antennae  is  well  developed,  the  first 
pair  being  rudimentary. 

(c)  The  mouth  appendages  are  small.  They  consist  of 
mandibles,  two  pairs  of  maxillae,  and  one  pair  of  maxillipeds. 

(d)  How  many  walking  legs  are  there?  Are  these  all 
alike? 

(e)  Notice  the  character  and  number  of  the  abdominal 
appendages.  On  the  posterior  surface  of  all  but  the  last  pair, 
which  are  modified  to  form  anal  feelers,  are  gills.  These  are 
the  only  respiratory  organs.  Why  must  these  animals  live 
in  damp  places? 

Make  a  drawing  of  the  animal  from  the  ventral  side. 

CAPRELLA  (Goat  Shrimp) 

These  animals  are  very  common  on  hydroids,  but  because 
of  their  peculiar  shape  and  slow  motions  are  rather  incon- 
spicuous. Watch  the  animals  and  see  how  they  move.  Is 
the  body  kept  at  rest  and  moved  by  the  action  of  the  ap- 
pendages, or  how  is  movement  from  place  to  place  effected? 
Are  the  appendages  adapted  for  grasping?  Watch  specimens 
and  see  if  you  can  determine  on  what  they  feed. 

The  form  is  of  interest  because  of  its  extreme  modifica- 
tion to  suit  it  to  the  needs  of  its  life.  There  is  some  difference 
in  the  structure  of  the  male  and  female. 

1.  Count  the  segments  of  the  body.     Do  they  differ  in 


ONISCUS,    CAPRELLA,    BRANCHIPUS  185 

number  and  shape  in  male  and  female?  The  first  represents 
the  head  with  two  fused  thoracic  segments.  The  abdomen 
forms  a  minute  protuberance  at  the  posterior  end  of  the  body. 

2.  At  the  anterior  end  of  the  body  are  the  eyes,  two  pairs 
of  antennae,  a  pair  of  maxillipeds,  and  a  pair  of  legs. 

3.  At  the  hinder  part  of  the  body  are  three  pairs  of  legs. 

4.  Near  the  middle  of  the  body  of  the  female,  and  near 
the  anterior  end  in  the  male,  is  another  pair  of  legs. 

5.  On  two  of  the  segments  which  do  not  bear  legs  are 

gills. 

If  time  'permits,  make  a  drawing. 

BRANCHIPUS  (Fairy  Shrimp) 

These  animals  may  be  found  in  pools  of  fresh  water  in 
the  early  spring,  just  as  the  ice  is  leaving.  Their  method  of 
swimming  by  means  of  the  large,  expanded  appendages  should 
be  observed. 

1.  Into  what  parts  does  the  body  seem  to  be  divided? 
Do  all  of  these  parts  show  segmentation? 

2.  Find  the  following  organs. 

(a)  The  stalked,  prominent  eyes. 

(b)  The  antennae.  In  the  female  the  first  are  slender 
and  the  second  vestigial.  In  the  male  the  first  are  slender 
and  the  second  are  enormously  enlarged  to  form  a  clasping 
organ. 

(c)  The  labrmn  forms  an  upper  lip. 

{d)  The  mandibles,  beneath  the  labrum  and  by  the  sides 
of  the  mouth.    Do  they  have  cutting  edges? 

(e)  Vestigial  maxillae  behind. the  mouth. 

(/)  Swimming  appendages.  How  many  are  there?  Notice 
the  fringe  of  hairs  on  each.  What  are  these  for?  Remove 
one  and  examine  it  with  a  microscope.  The  lobes  have  been 
described  as  exopod  and  endopod,  but  their  exact  relation- 
ship is  not  certain. 

A  drawing  is  desirable. 


186  ARTHROPODA 

DAPHNIA 

This  small  fresh-water  form  frequently  occurs  in  large 
numbers  in  small  pools  and  brooks.  Determine  how  it  swims. 
Being  small  and  transparent,  it  may  be  satisfactorily  studied 
with  a  compound  microscope. 

1.  Notice  the  shape  and  extent  of  the  protective  covering. 
To  what  part  of  other  crustaceans  does  this  correspond?  Are 
the  appendages  and  the  abdomen  capable  of  being  thrust 
out?    Are  there  any  signs  of  segmentation  of  the  body? 

2.  Determine  what  parts  are  used  in  keeping  a  current  of 
water  passing  through  the  shell.  Why  is  such  a  current 
needed? 

3.  If  the  animal  carries  young,  notice  how  they  are  kept 
in  the  brood  chamber  by  a  spine  that  extends  up  from  the 
dorsal  portion  of  the  base  of  the  abdomen. 

4.  Notice  the  beating  of  the  heart. 

5.  Are  the  eyes  stalked  or  sessile?  They  frequently  show 
a  peculiar  reaction  to  light.  If  the  light  is  cut  off  from  the 
microscope,  the  eye  will  be  seen  to  rotate  on  its  axis.  If  the 
light  is  admitted  again,  the  eye  rotates  back  to  its  original 
position. 

6.  The  first  antennae  are  very  small  and  project  ven- 
trally.    What  is  the  chief  function  of  the  second  antennae? 

7.  Several  appendages  will  be  seen  inside  of  the  shell,  but 
it  is  hard  to  determine  their  exact  relation.  The  functions 
of  some  of  them  may  be  apparent. 

A  drawing  is  desirable. 

CYCLOPS  (Water-flea) 

Almost  any  free-swimming  copepod,  either  fresh  water  or 
marine,  will  answer  quite  as  well  as  the  fresh-water  Cyclops. 

Cyclops  may  be  found  in  almost  any  pool  of  fresh  water 
and  the  marine  forms  are  among  the  most  abundant  of  the 
animals  of  the  sea.  Surface  skimming  of  the  sea,  made  with 
a  net  composed  of  cheese  cloth  or  silk  bolting  cloth,  will 
yield  an  abundance  of  material. 


DAPHNIA,  CYCLOPS,  ARGULUS  187 

1.  Watch  the  animals  and  see  how  they  swim.  With  a 
pipette  try  to  catch  a  certain  individual  and  see  whether  the 
jerky  movements  probably  aid  these  animals  in  escaping 
enemies.     Determine  what  organs  are  used  in  swimming. 

2.  With  a  microscope  examine  specimens  that  have  been 
confined  under  a  cover  glass,  and  notice  the  shape  of  the 
body.  Into  what  parts  is  it  divided?  Count  the  number  of 
segments.  Look  for  evidence  of  fused  segments.  Notice  how 
the  spines  on  the  abdomen  are  arranged. 

3.  Do  you  find  eyes  that  are  equivalent  to  the  usual  ar- 
thropod eyes?  Do  you  find  an  eye  spot?  If  such  a  spot  is 
found,  determine  its  position  and  shape. 

4.  Which  pair  of  antennae  is  larger?  Why  are  the  large 
antennae  fringed  with  spines? 

5.  Are  there  thoracic  or  abdominal  appendages?  Are  any 
appendages  other  than  the  first  antennae  used  in  swimming? 

6.  The  mouth  parts  consist  of  mandibles  and  two  maxillae. 

7.  If  the  specimen  is  a  female  it  may  have  two  large  egg 
sacs  attached  to  the  sides  of  the  base  of  the  abdomen.  The 
female  has  two  of  the  abdominal  segments  fused.  In  the 
male  the  segments  are  free. 

A  drawing  of  the  specimen  is  desirable. 

Fish:   Seasonal  Distribution  of  the  Plankton  of  the  Woods  Hole  Region. 

Bull.  Bur.  Fisheries,  vol.  41,  Doc.  975,  1925. 
Heath:     The    External    Development    of   Certain    Phyllopods.      Jour. 

Morph.,  vol.  38,  No.  4,  1924. 
Sharpe :    Notes  on  the  Marine  Copepods  and  Cladocera  of  Woods  Hole 

and  Adjacent  Regions,  Including  a  Synopsis  of  the   Genera   of  the 

Harpocticoida.     Proc.  U.  S.  Nat.  Mus.,  38,  1910. 
Wheeler:    Free-Swimming  Copepods  of  the  Woods  Hole  Region.    Bull. 

U.  S.  Fish  Com.,  19,  1899. 

ARGULUS  (Fish-louse) 

These  animals  may  be  found  on  many  species  of  fresh- 
water and  marine  fish.  Notice  their  shape  and  determine 
how  they  cling  to  their  host.  Are  they  able  to  crawl?  Can 
they  swim? 


188  ARTHROPODA 

Find: 

1.  Into  what  regions  can  the  body  be  divided? 

2.  The  eyes,  the  eye  spot,  and  the  two  pairs  of  small  an- 
tennae. 

3.  The  sucking  proboscis,  composed  of  mandibles  and 
maxillae,  which  lies  between  the  suckers. 

4.  The  suckers,  which  are  the  modified  second  maxillae. 

5.  The    posterior    (third)     maxillipeds    just    behind    the 

suckers. 

6.  Four  pairs  of  biramous  thoracic  appendages.    What  is 

their  function? 

Make  a  drawing  of  the  animal. 

Wilson:    The  Fish  Parasites  of  the  Genus  Argulus  Found  in  the  Woods 
Hole  Region.    Bull.  U.  S.  Bur.  Fish.,  24,  1904. 

LEPAS  (Goose  Barnacle) 

If  possible,  examine  a  cluster  of  specimens  as  they  natu- 
rally occur  attached  to  floating  timber. 

1.  Account  for  the  fact  that  the  peduncles  are  much  larger 
in  some  specimens  than  in  others.  Are  they  contractile  so 
the  body  may  be  moved  into  different  positions?  Would 
such  movements  be  of  value? 

2.  Notice  the  thoracic  appendages.  Can  they  be  thrust 
from  the  shell?  What  is  their  character?  What  are  their 
characteristic  movements?  Drop  a  small  piece  of  clam  meat 
on  these  appendages  of  a  living  specimen  and  see  what  hap- 
pens.   What  kind  of  food  would  they  naturally  collect? 

3.  Examine  the  portions  of  the  shell.  The  portion  on  the 
closed  margin  is  the  carina,  laterally  and  near  the  base  of 
the  peduncle  are  the  scuta,  and  near  the  extremity  the  terga. 
Why  are  there  so  many  pieces?  Notice  the  lines  of  growth 
and  determine  the  direction  of  growth  of  each  piece. 

Draw  the  animal  as  seen  from  one  side. 

Carefully  remove  the  carina  and  with  a  scalpel  or  razor 
cut  a  preserved  specimen  into  right  and  left  halves,  extend- 
ing the  cut  through  the  peduncle. 

4.  The  mouth  will  be  seen  at  the  end  of  a  rather  thick 


LEPAS,    LIMULUS  189 

prolongation  which  extends  to  near  the  bases  of  the  abdominal 
appendages.  On  the  margin  of  this  prolongation  are  the 
small  scalelike  mandibles,  first  maxillae,  and  second  maxillae. 
The  stomach  is  rather  large  and  the  small  intestine  leads  to 
the  posterior  end  of  the  abdomen,  where  it  opens  between 
the  abdominal  appendages. 

5.  The  nervous  system,  consisting  of  a  large  pair  of 
cerebral  ganglia  and  a  short  ventral  chain  of  ganglia,  should 
be  seen  in  such  a  section. 

6.  The  animal  is  hermaphroditic.  The  testes  lie  dorsal 
to  the  stomach  and  communicate  with  a  conspicuous  coiled 
vas  deferens  that  is  continued  to  the  elongated  penis  at  the 
end  of  the  abdomen.  What  need  is  there  for  such  a  long 
penis?  The  ovary  occupies  the  interior  of  the  peduncle. 
The  oviducts  are  inconspicuous  and  hard  to  follow.  They 
open  near  the  bases  of  the  anterior  thoracic  appendages.  An 
ovigerous  mass  may  sometimes  be  found  lying  between  the 
body  and  mantle.  Remove  some  of  this,  place  on  a  slide, 
cover,  and  examine  with  the  compound  microscope. 

7.  Examine  the  appendages  carefully  and  be  sure  that 
you  understand  the  relation  of  parts.  Remove  the  thoracic 
appendages  one  by  one  on  one  side  only.  What  part  must 
the  peduncle  represent?  Note  the  beautiful  adaptation  of  the 
animal  for  its  life. 

A  drawing  showing  the  organs  is  desirable. 

Bigelow:  Early  Development  of  Lepas.  Bull.  Mus.  Comp.  Zool.  Har- 
vard, 40,  1902. 

Delage:  Evolution  de  la  Sacculine.  (Sacculina  carcini.)  Arch.  Zool. 
Exp.  et  Gen.,  2e  Series,  11,  1884. 

ARACHNIDA 

LIMULUS  (Horseshoe  Crab) 

Notice  the  way  in  which  the  animal  crawls  upon  the  bot- 
tom. Is  it  well  protected  from  enemies?  Examine  it  care- 
fully for  parasites  and  for  animals  that  are  attached  to  it. 
Disturb  it  and  see  if  it  will  swim.    The  animals  are  usually 


190  ARTHROPOD A 

quite  active  in  the  evening,  and  if  you  visit  a  car  in  which 
they  are  kept,  at  this  time  of  the  day,  you  are  likely  to  find 
them  crawling  up  the  sides,  falling  over  and  swimming  on 
their  backs.  In  this  position  it  is  easy  to  determine  how 
they  swim.  The  animals  are  very  hardy  and  will  stand  even 
complete  removal  from  the  water  for  days  at  a  time.  During 
the  spring  and  early  summer,  eggs  are  deposited  in  the  sand; 
the  male  holding  to  the  edge  of  the  abdomen  of  the  female 
with  claws  modified  for  the  purpose,  is  dragged  after  her. 
If  possible,  the  method  of  egg  deposition  and  fertilization 
should  be  observed. 

1.  The  animal  consists  of  a  hoof-shaped  cephalothorax, 
an  abdomen,  and  a  caudal  spine.  How  are  these  joined?  Is 
there  any  indication  of  segmentation  of  any  of  them? 

2.  Examine  the  eyes  with  a  lens  and  see  that  they  are 

compound. 

3.  On  the  lower  side  of  the  cephalothorax  notice  the  ap- 
pendages. Are  they  all  built  on  the  same  plan?  Compare 
them  in  male  and  female.  Do  you  know  what  the  modifica- 
tions are  for?  Compare  the  pincers  with  those  of  a  lobster. 
The  first  pair  of  appendages  is  called  the  chelicerae.  Be- 
tween the  bases  of  the  last  pair  of  walking  legs  are  the 
chilaria.  Behind  the  chilaria  is  the  broad  flat  operculum. 
Does  this  show  evidence  of  being  modified  appendages? 
What  is  its  function? 

4.  Between  the  bases  of  the  cephalothoracic  appendages 
is  the  mouth.  Do  the  bases  of  the  appendages  show  any 
modifications  that  may  serve  as  teeth?  Can  the  pincer- 
bearing  appendages  be  so  bent  as  to  be  used  in  feeding? 

5.  Along  the  sides  of  the  abdomen  notice  the  movable 
spines.     How  many  are  there? 

6.  Under  the  operculum  are  the  gills.  How  many  groups 
are  there?  Are  they  arranged  in  pairs?  How  are  they  at- 
tached to  the  body?  Are  they  movable?  What  reason  is 
there  for  moving  them?  Examine  a  bunch  of  gills,  frequently 
called  a  gill  book,  and  see  how  it  is  formed. 


LIMULUS  191 

7.  At  the  base  of  the  caudal  spine  notice  the  anus. 

Make  a  drawing  of  the  ventral  surface. 

Internal  Anatomy. — If  the  Limulus  is  alive  the  simplest 
method  of  killing  it  in  preparation  for  dissection  is  to  cut 
off  the  legs  and  allow  the  blood  to  drain  off  from  the  large 
blood  sinuses  which  extend  into  each  leg. 

In  order  best  to  remove  the  heavy  carapace  it  is  desir- 
able to  make  several  cuts  in  the  exoskeleton  with  a  hacksaw 
or  a  fine-toothed  saw.  (For  an  outline  showing  a  good 
method  of  making  the  cuts,  see  Cole.)  With  cuts  properly 
made  lift  a  corner  of  the  carapace  slightly,  and  with  scalpel 
cut  away  the  adhering  tissue.  Use  short  cuts  and  keep  the 
cutting  edge  close  to  the  inner  surface  of  the  exoskeleton. 
With  the  carapace  raised  in  the  region  of  the  compound 
eyes  it  is  possible  to  see  the  nerves  leading  to  these  organs. 
When  the  piece  of  the  cephalothoracic  exoskeleton  has  been 
cut  free  from  adhering  tissue,  the  ligament  along  its  pos- 
terior border  should  be  cut  and  the  entire  piece  removed.  In 
cutting  these  ligaments  be  careful  not  to  cut  too  deep  for 
the  heart  lies  close  to  the  surface  at  this  point.  It  is  best 
to  remove  the  abdominal  exoskeleton  by  beginning  at  the 
posterior  end.  Cut  the  inter  articular  membranes  at  the  base 
of  the  telson  and  lift  the  abdominal  carapace  slightly.  The 
two  rows  of  depressions  seen  on  the  surface  of  the  latter  in- 
dicate the  position  of  chitinous  infoldings  of  the  exoskeleton, 
called  entapophyses.  The  heart  lies,  in  large  part,  between 
these  rows.  Slip  the  scalpel  (or  a  small  pair  of  bone 
forceps)  under  the  exoskeleton  and  cut  the  entapophyses  one 
at  a  time.  The  exoskeleton  may  now  be  separated  from  the 
soft  tissues  underneath  and  removed.  The  animal  should 
now  be  placed  in  a  large  crystallization  dish  and  the  rest  of 
the  dissection  carried  out  under  sea  water. 

The  Circulatory  System. — Remove  such  portions  of  the 
gonads  (orange  masses)  and  liver  tissue  (yellow  masses)  as 
may  cover  the  heart  and  major  blood  vessels.  The  heart 
will  now  be  seen  as  a  long  tubular  organ  lying  enclosed  in 


192  ARTHROPODA 

the  pericardium.  Locate  the  eight  pairs  of  ostia,  which  are 
transverse,  slitlike  valves  opening  from  the  pericardium  into 
the  heart.  Note  the  median  and  the  two  lateral  cardiac 
nerves  lying  on  the  pericardium.  From  the  anterior  end  of 
the  heart  extend  the  median  frontal  artery  and  the  two  lateral 
aortic  arches.  The  former  extends  forward  and  downward 
and  branches  into  two  marginal  arteries.  The  aortic  arches 
pass  down  on  either  side  of  the  proventriculus  and  follow 
the  esophagus  to  the  nerve  collar.  Here  the  vascular  system 
widens  to  enclose  the  collar,  then  extends  posteriorly,  en- 
closing the  ventral  cord  (vascular  ring  and  ventral  artery). 
Branches  from  the  ventral  artery  supply  the  telson. 

Along  the  sides  of  the  anterior  half  of  the  heart  may  be 
found  four  pairs  of  lateral  arteries.  These  are  valved  tubes 
leaving  the  heat  just  beneath  the  first  four  pairs  of  ostia. 
The  lateral  arteries  on  either  side  lead  into  a  collateral  ar- 
tery extending  in  a  posterior  direction.  Each  of  the  col- 
lateral arteries  gives  off  branches  going  to  the  muscles  and 
the  hemal  surfaces  of  the  body,  and  other  branches  (directed 
toward  the  median  line)  to  the  digestive  tube.  The  two  col- 
lateral arteries  unite  just  behind  the  heart  to  form  the 
superior  abdominal  artery.  Branches  of  this  artery  anas- 
tomose with  branches  of  the  ventral  aorta. 

Five  pairs  of  branchiocardiac  canals  or  sinuses  bring 
blood  from  the  gills  to  the  pericardial  sinus.  The  first  of 
these  receives  blood  from  the  operculum  and  the  first  gill; 
the  remaining  four  receive  blood  from  gills  2,  3,  4,  and  5 
respectively. 

The  remaining  portions  of  the  circulatory  system  are  not 
so  easily  seen,  but  will  be  mentioned  for  the  sake  of  com- 
pleteness. The  vascular  ring  supplies  blood  to  the  appen- 
dages of  the  cephalothorax.  The  ventral  artery  supplies  the 
gills.  Blood  from  all  parts  of  the  body  collects  in  a  pair  of 
longitudinal  sinuses  which  lead  to  the  gills. 

The  Digestive  System. — Remove  the  heart  and  such  gonad 
and  liver  tissues  as  lie  in  the  way.  Observe  the  large  sac- 
like proventriculus  or  stomach,  extending  into  the  anterior 


LIMULUS  193 

part  of  the  cephalothorax.  If  this  organ  be  pushed  to  one 
side  it  is  possible  to  see  the  esophagus  leading  from  the 
mouth  forward  to  the  under  side  of  the  stomach.  Turning 
now  to  the  more  posterior  parts  of  the  digestive  tube,  it  will 
be  seen  that  the  stomach  leads  directly  into  the  long,  straight 
intestine.  The  latter  ends  in  a  muscular  rectum,  which  opens 
to  the  exterior  through  the  anus.  If  the  esophagus,  stomach 
and  pyloric  valve  be  split  open,  the  strongly  ridged  chitinous 
lining  may  be  seen.  The  intestine,  on  the  other  hand,  has  a 
glandular  lining.  On  each  side  of  the  intestine  may  be  found 
a  pair  of  hepatic  ducts  which  convey  fluids  from  the  liver  to 
the  lumen  of  the  intestine. 

The  Nervous  System. — Sever  the  digestive  tube  at  the 
rectum  and  again  at  the  junction  of  the  esophagus  and 
stomach.  Carefully  remove  this  section  of  the  tube.  The 
endocranium  (a  cartilaginous  shelf  supposed  to  be  homol- 
ogous with  the  cartilaginous  brain  case  of  certain  verte- 
brates) is  in  clear  view.  This  should  be  removed  carefully 
to  expose  the  underlying  brain  or  nerve  collar.  The  esopha- 
gus is  completely  encircled  by  the  brain.  Note  an  anterior 
enlargement,  the  frontal  lobe  or  forebrain.  Three  olfactory 
nerves  and  a  nerve  to  the  median  eye  are  given  off  from  its 
anterior  end.  Arising  from  the  hemal  surface  of  the  fore- 
brain  are  a  pair  of  lateral  eye  nerves  and  a  pair  of  smaller 
lateral  or  first  hemal  nerves.  Behind  the  latter  are  seven 
pairs  of  hemal  nerves  radiating  from  the  nerve  ring.  A 
pair  of  stomodeal  nerves  arise  from  the  inner  anterior  edge 
of  the  nerve  ring. 

The  nerves  so  far  described  are  those  the  origins  of  which 
may  be  seen  when  the  brain  is  in  situ.  All  nerves  should  be 
fully  exposed  and  traced  to  the  organs  which  they  supply. 
Schaudinn's  fluid  may  be  used  to  whiten  the  nervous  tissue. 
(Note:    this  solution  is  poisonous.) 

It  is  desirable  to  draw  the  nervous  system-  in  situ. 

Further  study  of  the  nervous  system  may  be  made  by 
removing  the  brain  and  nerve  cord.  To  remove  the  brain  and 
13 


194  ARTHROPODA 

cord,  dissect  the  esophagus  from  the  nerve  ring;  free  the 
nerve  cord  from  the  cartilaginous  bridges  that  extend  across 
it  at  intervals;  sever  the  main  nerves  at  some  distance  from 
the  brain  and  cord;  lift  the  entire  central  nervous  system  out 
and  place  it  in  a  crystallization  dish. 

Before  this  system  is  further  studied  it  should  be  hardened 
and  whitened.  First  arrange  the  brain,  cord  and  nerves  in 
a  normal  position  and  cover  the  system  with  a  piece  of  dry 
newspaper.  Hold  the  paper  in  place  with  the  fingers  and 
slowly  pour  over  it  enough  5  per  cent  formalin  just  to  cover 
the  paper.  In  about  half  an  hour  the  nervous  tissue  will  be 
hard  and  white.  The  preparation  may  then  be  turned  to 
expose  the  neural  surface  of  the  brain  and  cord,  and  the 
origins  of  the  neural  nerves. 

Note  the  preoral  commissure  extending  across  the  nerve 
ring  anterior  to  the  position  occupied  by  the  esophagus. 
The  commissure  gives  off  three  rostral  nerves  directed 
caudad.  Find  four  postoral  commissures,  the  last  three  of 
which  are  fused.  Just  behind  the  forebrain  arises  a  pair  of 
cheliceral  nerves.  Five  pairs  of  large  nerves  are  given  off 
from  the  nerve  ring  to  the  next  five  thoracic  appendages. 
Each  of  these  gives  off  a  neural  mandibular  branch  and 
several  hemal  entocoxal  branches.  Two  pairs  of  small 
nerves  are  given  off  from  the  posterior  part  of  the  nerve  ring 
at  points  neural  to  the  origin  of  the  nerve  cord.  These  are 
the  chilarial  and  opercular  nerves. 

The  double  nerve  cord  extends  into  the  abdomen.  Here 
may  be  found  5  pairs  of  ganglia,  and  a  terminal  knot  con- 
sisting of  3  pairs  of  ganglia  closely  fused.  Each  of  the  first 
five  pairs  of  ganglia  gives  off  a  pair  of  hemal  nerves  directed 
cephalad,  and  a  pair  of  neural  nerves  directed  caudad. 
Usually  the  neural  nerves  are  lacking  in  the  last  3  pairs  of 
ganglia.  The  3  pairs  of  hemal  nerves  are  spread  fan-wise. 
The  pair  nearest  the  median  line  innervates  the  telson. 

Make  a  drawing  of  the  nervous  system  from  the  neural 
aspect. 


LIMULUS,    BUTHUS  195 

The  Excretory  System. — The  coxal  glands  lie  one  on  each 
side  of  the  endocranium.  They  may  be  recognized  by  their 
brick-red  color.  Lobes  extend  into  the  bases  of  the  second, 
third,  fourth  and  fifth  pairs  of  appendages.  A  duct  leads 
from  each  of  the  last  pair  of  lobes,  opening  on  the  posterior 
face  of  the  fifth  appendage. 

Cole:  Preliminary  Dissection  of  Limulus.  Collecting  Net,  9,  1934. 
Lankester:  Limulus  an  Arachnid.  Quart.  Jour.  Mic.  Sci.,  21,  1881. 
Packard:    The  Anatomy,  Histology,  and  Embryology  of  Limulus  poly- 

phemus.    Mem.  Bost.  Soc.  Nat.  Hist.,  1880. 
Patten  and  Redenbaugh:    Studies  on  Limulus,  Jour.  Morph.,  16,  1899. 
Zittel:     Text-book   of   Paleontology.     Macmillan   and   Co.,  Ltd.,   1913. 

BUTHUS  (Scorpion) 

Living  specimens  of  these  animals  are  not  usually  avail- 
able for  laboratory  study.  They  live  for  the  most  part  con- 
cealed during  the  day  under  old  bark  and  in  crevices  and 
holes  and  are  active  at  night.  Their  food  is  largely  spiders 
and  insects  which  are  seized  by  the  claws  and  killed  with 
the  abdominal  sting. 

1.  Into  what  parts  is  the  body  divided?  How  many  seg- 
ments are  recognizable?    Which  are  the  most  freely  movable? 

2.  Look  for  eyes.    Do  you  find  any  besides  the  large  pair? 

3.  Find  four  pairs  of  slitlike  openings  on  the  ventral  side 
of  the  pre-abdomen.  These  are  the  stigmata,  the  openings 
of  the  lung  books. 

4.  Find  the  following  appendages: 

(a)  The  chelicerae.  What  is  their  structure  and  where 
are  they  placed? 

(b)  The  pedipalpi.  Compare  them  with  the  chelicerae 
and  count  their  segments. 

(c)  Four  pairs  of  walking  legs.  Count  their  segments 
and  see  if  they  are  armed  with  claws. 

(d)  The  comb-shaped  pectines.  Are  they  on  the  thorax 
or  the  abdomen?    Their  function  is  doubtful. 

5.  Examine  the  mouth.  Are  there  any  jaws?  Is  a  labrum 
present? 


196  ARTHROPODA 

6.  Find  the  position  of  the  anus.  The  terminal  spine  is 
provided  with  a  poison  gland  and  serves  as  a  sting.  In  the 
living  animal,  the  postabdomen  is  habitually  carried  over  the 
back. 

Make  a  drawing  of  the  under  side  of  a  specimen. 

EPEIRA  (Round-web  Spider) 

Examine  the  webs  of  different  species  of  spiders  and  see 
how  they  are  constructed.  Do  all  of  the  webs  have  places 
for  the  concealment  of  the  owners?  Do  all  spiders  seem  to 
construct  definite  webs  for  the  capture  of  insects?  How  do 
spiders  entangle  insects  in  their  webs?  Do  different  kinds 
use  different  methods?    What  parts  of  insects  are  eaten? 

By  destroying  webs  that  are  occupied  by  spiders  that  are 
in  convenient  places  for  observation,  the  construction  of  new 
webs  may  be  observed.  Notice  how  the  framework  of  a  round 
web  is  laid  and  then  how  the  threads  are  attached  to  the 
framework.  Are  any  of  the  legs  used  in  handling  the  thread? 
Are  spiders  equally  active  at  all  times  of  the  day? 

Spiders'  webs  may  frequently  be  seen  floating  in  the  air, 
especially  in  the  late  summer  or  autumn.  By  watching 
spiders  that  are  on  fences  and  bushes  the  formation  of  these 
threads  may  be  observed.  Watch  such  a  spider  and  see  if  you 
can  determine  the  use  to  which  the  thread  is  put. 

Capture  a  spider  and  watch  it  descend  by  a  thread. 
Where  is  the  thread  formed?  Does  the  spider  hold  to  it  with 
its  legs?  Keep  taking  the  thread  up  so  that  the  spider  can- 
not reach  the  ground,  and  see  if  there  is  a  limit  to  the 
amount  that  can  be  formed.  When  the  spider  starts  to  climb 
the  thread  see  how  this  is  done,  and  whether  the  thread  is 
taken  up  as  the  animal  climbs  or  is  allowed  to  float  free. 

Find  where  spiders  lay  their  eggs.  Some  carry  them.  If 
you  can  find  a  specimen  with  an  egg  sac,  see  how  it  is  carried 
and  whether  it  will  drop  its  eggs  when  frightened.  Remove 
the  egg  sac  and  see  if  the  spider  will  accept  it  again.    Open 


EPEIRA 


197 


several  egg  sacs  and  see  if  the  eggs  all  appear  to  be  in  the 
same  stage  of  development. 

Study  the  movements  of  the  animal  and  see  how  many  of 
the  appendages  are  used  in  locomotion.  Are  any  of  the  ap- 
pendages used  sometimes  for  locomotion  and  sometimes  for 

feeling? 

Examine  the  external  structure  of  Epeira. 

1.  Into  what  parts  is  the  body  divided?  Do  both  parts 
bear  appendages? 

2.  Look  for  eyes  on  the  anterior  end  of  the  body.  How 
many  are  there?  Do  they  seem  to  be  simple  or  compound? 
Determine  whether  a  specimen  can  see. 

3.  The  following  appendages  should  be  found: 

(a)  The  chelicerae  or  mandibles.  Notice  their  structure 
and  see  that  each  ends  in  a  sharp  claw.  The  poison  gland  dis- 
charges at  the  tip  of  this  claw. 

(b)  The  pedipalpi  or  palpi.  How  many  segments  have 
they?  Examine  their  tips  for  claws.  What  are  they  appar- 
ently used  for? 

(c)  Four  pairs  of  legs.  Are  they  all  alike?  Count  the 
segments  and  examine  their  tips  for  claws. 

(d)  On  the  abdomen,  three  pairs  of  spinnerets.  Notice 
their  positions  and  see  if  they  are  segmented.  Understand 
their  function  and  whether  they  are  all  used  at  the  same 
time.    They  are  probably  true  abdominal  appendages. 

4.  On  the  lower  surface  of  the  abdomen,  near  its  anterior 
end,  are  two  slits,  the  openings  into  the  lung  sac  or  lung 
books.    They  are  respiratory  in  function. 

5.  Just  in  front  of  the  spinnerets  is  a  minute  median  pore, 
the  spiracle,  that  is  often  very  hard  to  find.  It  is  the  external 
opening  of  a  series  of  abdominal  tracheae. 

Make  a  drawing  of  a  ventral  view. 

Baerg:    The  Black  Widow;   Its  Life  History  and  the  Effects   of  the 

Poison.    Sci.  Mo.,  vol.  17,  1923. 
Comstock:    The  Spider  Book,  1913. 
Emerton:    New  England  Spiders.     Trans.  Conn.  Acad.     Many  papers, 

1882-1915. 


198  ARTHROPODA 

Montgomery :    Studies  on  the  Habits  of  Spiders,  Particularly  Those  of 
the  Mating  Period.    Proc.  Acad.  Nat.  Sci.,  Philadelphia,  1903. 

:    On  the  Spinnerets,  Cribellum,  Colulus,  Tracheae  and  Lung-books 

of  Araneads.    Proc.  Acad.  Nat.  Sci.,  Philadelphia,  1909. 

The  Development  of  Theridium,  an  Aranead,  up  to  the  Stage  of 


Reversion.     Jour.  Morph.,  20,  1909. 

The  Significance  of  the  Courtship  and  Secondary  Sexual  Charac- 


ters of  Araneads.    Am.  Nat.,  44,  1910. 
Peckham:    Observations  on  Sexual  Selection  in  Spiders  of  the  Family 

Attidae.     Occas.  Papers  Nat.  Hist.  Soc,  Wisconsin,  1  and  2. 
Wood:   Autotomy  in  Arachnida.     Jour.  Morph.,  vol.  42,  No.  1,  1926. 

PHOXICmLIDIUM 

The  exact  affinities  of  the  pycnogonids  to  other  forms  is 
not  known,  but  they  have  certain  characters  that  have  sug- 
gested a  possible  relationship  to  the  Arachnida.  They  are 
frequently  found  in  considerable  abundance  on  the  material 
that  is  attached  to  piles.  Notice  their  movements  and  see 
how  they  cling  to  the  material  on  which  they  are  moving. 

1.  The  body  is  very  slender  and  is  composed  of  a  number 
of  free  segments  that  form  the  head  and  thorax  and  a  small, 
vestigial  abdomen.  How  many  free  segments  are  there?  At 
the  anterior  end  is  a  rather  prominent  proboscis,  with  the 
mouth  at  its  end. 

2.  The  following  appendages  will  be  found: 

(a)  The  chelicerae.  What  is  their  structure?  Are  they 
armed  with  pincers? 

(£>)  Four  pairs  of  long  walking  legs.  How  many  seg- 
ments have  they?  The  viscera  extend  into  the  bases  of  these 
appendages. 

(c)  The  male  is  provided  with  a  pair  of  ventral  appen- 
dages called  the  ovigerous  legs,  by  means  of  which  the  eggs 
are  collected  as  they  are  laid  by  the  female.  These  appen- 
dages are  not  present  in  the  female. 

Make  a  drawing  of  the  under  side  of  a  specimen. 

Cole:    Pycnogonidia  of  the  West  Coast  of  North  America.    Harriman 
Alaska  Exped.,  10,  1904. 


PHOXICHILIDIUM,    LITHOBIUS,    JULUS  199 

MYRIAPODA 
LITHOBIUS  (Centipede,  Earwig) 

These  animals  may  frequently  be  found  under  stones,  logs 
or  boards,  or  about  rubbish  or  manure  heaps.  They  live 
largely  on  insects,  larvae,  and  small  worms,  and  are  very 

active. 

1.  Notice  the  shape  of  the  body  and  count  the  number  of 
segments.    Is  there  a  distinct  head?    Are  the  segments  very 

movable? 

2.  How  many  appendages  does  each  segment  possess? 
Are  all  of  the  segments  provided  with  appendages?  Allow 
the  animal  to  run  and  see  how  the  legs  are  used.  Do  those  of 
a  side  all  move  in  the  same  direction  at  the  same  time?  Are 
all  of  the  legs  alike?  Notice  the  pair  of  appendages  just 
behind  the  head  and  see  how  they  differ  from  the  others. 
These  appendages  are  organs  of  prehension  that  are  used  in 
grasping  the  prey.  They  are  provided  with  poison  glands 
that  open  on  their  inner  sides  near  their  free  ends. 

3.  Examine  the  head  and  find  the  eyes,  antennae,  and 
mouth  parts.  The  latter  consist  of  a  labrum,  a  pair  of  man- 
dibles, and  two  pairs  of  maxillae,  the  last  pair  of  which  is 
united  to  form  a  labium. 

4.  Understand  how  the  animal  breathes.  The  stigmata 
are  situated  near  the  bases  of  the  legs,  but  are  hard  to  see 
except  in  favorable  specimens. 

Make  a  drawing  of  the  animal. 

JULUS  (Thousand-legs) 

These  animals  are  frequently  very  abundant  under  the 
dead  bark  of  logs  or  stumps,  in  decaying  wood,  and  in  decay- 
ing heaps  of  grass.  In  the  autumn  they  frequently  congre- 
gate under  boards  and  in  corners.  They  feed  largely  on 
decaying  vegetable  matter,  but  may  become  pests  in  gardens, 
destroying  tomatoes  and  fallen  fruits  and  many  vegetables. 

1.  Disturb  a  specimen  and  see  how  its  rolls  up.    Can  this 


200  ARTHROPODA 

be  protective?    See  if  there  is  any  odor  when  it  is  disturbed. 
What  purpose  can  such  an  odor  serve? 

2.  What  is  the  shape  of  the  body?  Is  it  hard  or  soft? 
How  many  segments  are  there? 

3.  How  many  appendages  are  borne  on  a  segment?  Do  all 
of  the  segments  bear  appendages?  Does  the  animal  move 
rapidly?  Does  the  first  pair  of  appendages  behind  the  head 
show  modifications  for  prehension?  Does  this  animal  need 
such  an  organ? 

4.  Compare  the  organs  of  the  head  with  those  of  the  pre- 
ceding form. 

Make  a  drawing  of  the  under  side  of  one  segment. 

Williams:   Habits  and  Structure  of  Scutigerella  immaculata.    Proc.  Bost. 
Soc.  Nat.  Hist.,  33,  1907. 

INSECTA 
ACRIDIUM  (Grasshopper) 

Study  grasshoppers  as  they  occur  in  nature  and  determine 
as  far  as  possible  the  following  points: 

1.  Do  they  see  or  hear?  Are  they  equally  sensitive  to 
touch  on  all  parts  of  the  body?  Are  these  animals  well  pro- 
vided with  sense  organs? 

2.  What  is  their  food?  Are  all  plants  eaten  or  are  some 
avoided?    See  how  the  mouth  parts  are  used  in  feeding. 

3.  What  are  the  important  enemies  of  grasshoppers?  How 
do  they  escape  their  enemies?  Do  they  hide?  Are  they  pro- 
tectively colored?  How  does  jumping  serve  them  better  than 
crawling?  How  many  times  its  length  can  a  grasshopper 
jump? 

4.  During  late  summer  and  autumn  you  may  find  indi- 
viduals depositing  eggs.  See  if  you  can  determine  how  the 
end  of  the  body  is  worked  into  the  ground. 

For  study  it  is  desirable  to  use  a  rather  large,  freshly 
killed  or  alcoholic  specimen. 

The  body  is  divided  into  three  well-marked  regions. 


JULUS,    ACRIDIUM  201 

1.  The  Head.— Is  it  movable?  Does  it  need  to  be  as  mov- 
able as  your  own  head?    It  bears  several  organs. 

(a)  The  compound  eyes.  Examine  one  with  a  lens  or  re- 
move its  outer  covering  and  examine  it  with  a  compound 
microscope.  You  should  understand  the  structure  of  the 
whole  eye  and  how  it  gives  a  single  visual  image. 

(6)  The  ocelli,  three  in  number,  one  near  the  middle  of 
the  front  part  of  the  head  and  the  others  placed  near  the  bases 
of  the  antennae. 

(c)  The  antennae.  Why  are  they  so  flexible?  Examine 
one  with  a  microscope  and  notice  the  spines.    What  are  these 

for? 

{d)  Mouth  parts.    These  should  be  studied  later. 

2.  The  Thorax.— Why  should  it  be  large  and  comparatively 
firm?  This  portion  is  more  or  less  distinctly  divided  into 
three  parts,  each  of  which  carries  a  pair  of  legs. 

(a)  Compare  the  three  legs  on  one  side.  Do  they  have 
the  same  number  of  segments?  Do  all  of  the  joints  of  the  leg 
move  in  the  same  plane?  The  five  divisions  of  a  leg  are,  be- 
ginning with  the  basal  end:  coxa,  trochanter  (immovably 
joined  to  the  coxa  in  the  leaping  legs),  femur,  tibia,  and 
tarsus,  which  is  composed  of  four  movable  pieces.  Do  the 
femurs  of  the  leaping  legs  differ  from  the  femurs  of  the  other 
legs?  Account  for  this.  Determine  how  the  foot  is  arranged 
to  hold  to  objects.  Have  you  noticed  a  grasshopper  settle 
its  feet  preparatory  to  jumping?  Examine  the  joint  between 
the  femur  and  tibia. 

(£>)  Examine  the  wings  and  notice  their  size,  shape,  places 
of  attachment,  and  general  character.  Do  they  apparently 
have  different  functions  to  perform?  Notice  how  the  posterior 
wings  are  folded  so  that  they  may  be  covered  by  the  anterior. 
Does  this  seem  greatly  to  reduce  their  strength?1 

3.  The  Abdomen. — Count  the  number  of  segments.  Each 
one  is   covered   dorsally  by   a   tergum   and  ventrally  by   a 

1You  should  examine  the  posterior  wing  of  a  beetle  and  see  how 
it  is  folded. 


202  ARTHROPODA 

sternum.  Is  the  abdomen  more  movable  than  the  other  por- 
tions? Of  what  advantage  is  this  condition?  The  posterior 
ends  of  the  abdomens  of  male  and  female  differ.  This  portion 
of  the  female  is  modified  to  form  the  ovipositor,  which  con- 
sists of  two  large  pairs  of  plates  that  inclose  a  smaller  pair 
of  plates.  It  is  between  these  plates  that  the  oviduct  opens. 
What  advantage  lies  in  the  fact  that  the  larger  plates  possess 
hard  tips?  Along  the  sides  of  the  abdomen  notice  the 
stigmata,  the  external  openings  of  the  respiratory  system.  Do 
you  find  stigmata  on  other  parts  of  the  body? 

Draw  an  enlarged  side  view  of  a  grasshopper,  placing  the 
appendages  in  their  proper  positions. 

Mouth  Parts. — It  has  already  been  noticed  that  the  mouth 
parts  serve  to  cut  off  pieces  of  leaves,  which  are  then  passed 
directly  into  the  alimentary  canal.  For  such  a  purpose  there 
should  be  holding  as  well  as  cutting  parts. 

1.  Pass  a  needle  under  the  labrum,  which  forms  the  upper 
lip,  and  notice  that  it  is  hinged  and  that  the  end  is  lobed.  It 
is  not  supposed  to  be  homologous  with  usual  arthropod  appen- 
dages. With  fine  scissors  remove  it  and  place  it  in  a  watch 
glass  containing  water. 

2.  Immediately  behind  the  labrum  is  a  pair  of  hard,  dark- 
colored  organs,  the  mandibles,  that  are  used  in  cutting  the 
food.  Their  position  should  be  carefully  noted,  but  it  will 
be  better  to  leave  them  in  position  until  the  other  mouth 
appendages  have  been  removed. 

3.  Situated  by  the  side  of  the  mouth  and  just  behind  the 
mandibles  are  the  maxillae.  With  a  needle  push  one  to  one 
side  and  notice  that  it  consists  of  a  somewhat  flattened  por- 
tion with  a  jointed  maxillary  palp  at  one  side.  Carefully 
determine  the  positions  of  the  maxillae  with  relation  to  other 
parts.  What  possible  uses  are  served  by  the  two  parts?  Re- 
move them  with  scissors  and  place  them  in  the  watch  glass 
with  the  labrum,  in  approximately  their  relative  positions 
and  study  carefully. 

4.  Pass   a   needle   behind   the   remaining  appendage,   the 


ACRIDIUM  203 

labium,  and  see  that  it  is  hinged  and  forms  the  lower  lip. 
Remove  it  with  scissors  and  place  it  in  position  in  the  watch 
glass.  You  will  find  that  it  bears  a  pair  of  labial  palpi,  and 
that  there  is  a  deep  cleft  along  the  middle  line.  These  are 
indications  that  the  appendage  is  the  result  of  the  fusion  of  a 
pair  of  appendages  (the  second  maxillae). 

5.  Remove  the  mandibles  and  examine  their  cutting  mar- 
gins.   Place  them  in  position  in  the  watch  glass. 

Make  a  drawing  showing  the  structure  of  each  of  these 
appendages.  Arrange  your  figures  as  nearly  as  possible  in 
the  relative  positions  of  the  parts.1 

Internal  Structure. — Remove  the  wings,  and  before  open- 
ing the  body  notice  the  rather  large,  somewhat  transparent 
tympanum  on  each  side  of  the  first  abdominal  segment,  very 
near  the  base  of  the  leaping  leg.  The  structure  of  the  audit- 
ory organ  may  be  easily  studied  by  staining,  clearing,  and 
mounting  in  balsam.  (See  Packard's  "Text-Book  of  Entom- 
ology" or  Brooks's  "Hand-book  of  Invertebrate  Zoology.") 
Remove  the  dorsal  portion  of  the  wall  of  the  abdomen  and 
thorax,  and  notice: 

1.  The  heart,  which  will  be  found  attached  to  the  portion 
of  the  wall  of  the  abdomen  that  has  been  removed,  by  means 
of  numerous  radiating  muscle  fibers.  You  probably  will  not 
be  able  to  determine  the  structure  of  the  heart  in  the  dissec- 
tion. Read  this  up,  and  determine  what  the  radiating  muscle 
fibers  are  for. 

2.  The  space  between  the  muscles  and  the  viscera  is  filled 
more  or  less  completely  by  the  fat  body  and  the  tracheae. 
With  a  lens  notice  how  the  tracheae  connect  with  the  spiracles 
and  how  they  branch.  Remove  a  portion  of  the  tissue  in 
which  you  can  see  tracheae,  mount  it  in  water  under  a  cover, 
and    examine    it    microscopically.      Each    tracheal    tube    is 

1The  mouth  parts  of  insects  that  depend  on  biting  off  portions  of 
plants  for  food  are  similar.  Directions  for  the  study  of  the  mouth  parts 
of  the  honey-bee  are  given  further  on,  but  the  mouth  parts  of  other 
forms,  such  as  the  fly,  butterfly,  and  bug,  should  be  studied. 


204  ARTHROPODA 

marked  by  striations  wound  around  it.  Do  you  know  what 
causes  this  appearance  and  what  the  arrangement  is  for?  Do 
you  understand  how  the  tracheal  system  is  arranged?  What 
is  the  distribution  of  this  system  and  how  is  the  air  made  to 
go  in  and  out? 

3.  Near  the  dorsal  surface  of  the  posterior  part  of  the  ab- 
domen, surrounded  by  the  tissues  already  mentioned,  are  the 
gonads.  These  differ  in  size  and  shape  according  to  the  sex. 
In  the  male  the  vasa  deferentia  may  be  seen  leaving  the 
tabulated  testes.  In  the  female  the  oviducts  pass  around  the 
sides  of  the  intestine.    They  may  be  followed  later. 

4.  Loosen  the  anterior  ends  of  the  gonads  and  turn  them 
posteriorly  to  expose  the  hinder  part  of  the  alimentary  canal.1 

(a)  The  esophagus,  which  bends  backward  from  the 
mouth,  gradually  enlarges  as  it  enters  the  thorax. 

(b)  The  crop,  which  is  not  sharply  separated  from  the 
esophagus,  gradually  narrows  posteriorly. 

(c)  Following  the  constriction  posterior  to  the  crop  is  the 
elongated  stomach,  frequently  called  the  ventriculus.  Sur- 
rounding the  anterior  end  of  this  portion  is  a  series  of  rather 
large  diverticula,  the  gastric  caeca,  that  extend  both  ante- 
riorly and  posteriorly  from  the  points  where  they  open  into 
the  stomach. 

(d)  Some  distance  behind  the  posterior  ends  of  the  hepatic 
caeca,  quite  concealed  by  the  mass  of  small  uriniferous  tubes, 
is  a  slight  constriction  and  hardening  of  the  alimentary  canal 
that  marks  the  division  between  the  stomach  and  intestine. 
It  is  at  this  point  that  the  uriniferous  tubes  join  the  alimen- 
tary canal. 

(e)  Behind  the  intestine  the  alimentary  canal  becomes 
much  smaller  and  is  known  as  the  hind  intestine  or  colon. 

(/)  Behind  the  colon,  forming  the  hinder  portion  of  the 
alimentary  canal,  is  the  slightly  enlarged  rectum.    The  rectum 

1  There  is  great  diversity  in  the  parts  of  the  alimentary  canals  of 
different  insects.  This  is  correlated  with  the  great  differences  in  feed- 
ing habits. 


ACRIDIUM  205 

cannot  be  seen  until  the  ovary  is  removed,  which  should  be 
deferred  until  the  ducts  have  been  seen. 

Make  a  drawing  showing  the  position  of  the  parts  of  the 
alimentary  canal  in  side  view. 

Cut  the  intestine  and  turn  the  alimentary  canal  poste- 
riorly and  anteriorly. 

5.  Notice  the  muscles: 

(a)  That  move  the  abdominal  segments. 

(b)  That  move  the  legs  (those  that  supply  the  wings 
have  been  destroyed). 

(c)  That  move  the  jaws. 

Do  you  understand  now  why  the  thorax  needs  to  be 
comparatively  large  and  firm? 

6.  The  nervous  system  is  directly  comparable  to  that  of 
the  lobster,  but  the  connectives  between  the  ganglia  will  be 
found  to  be  distinctly  double  and  the  ganglia  to  be  somewhat 
differently  arranged.1 

The  ventral  chain  will  be  found  to  consist  of  a  pair  of 
sub  esophageal,  three  pairs  of  thoracic,  and  five  pairs  of  ab- 
dominal ganglia  with  the  connectives  between  them.  Which 
of  these  are  largest?  Why  is  this  the  case?  Trace  the  nerves 
from  them  and  see  what  organs  they  supply. 

Trace  the  connectives  forward  from  the  subesophageal  gan- 
glia and  see  that  they  pass  around  the  esophagus,  thus  form- 
ing the  circumesophageal  connectives.  Cut  away  the  dorsal 
portion  of  the  head  and  expose  the  cerebral  ganglia. 

Add  the  nervous  system  to  the  figure  that  shows  the  alim- 
entary canal. 

7.  Trace  the  oviducts  down  around  the  sides  of  the  body 
and  notice  that  they  unite  with  each  other  ventral  to  the  ner- 
vous system,  to  form  the  vagina.  This  may  be  traced  to  its 
opening  between  the  plates  of  the  ovipositor.  Dorsal  to  the 
vagina,  opening  to  the  exterior  very  near  it,  is  a  small  sac,  the 

xThe  arrangement  of  the  ganglia  in  insects  is  very  variable,  show- 
ing many  gradations  in  concentration. 


206  ARTHROPODA 

spermatheca,  which  serves  to  store  the  spermatozoa  received 
from  the  male  until  the  eggs  are  laid. 

The  reproductive  organs  may  also  be  added  to  your  figure 
showing  internal  anatomy. 

Lang:    Handbuch  der  Morphologie  der  wirbellosen  Tiere.    Bd.  4,  1921. 
Brooks:    Hand-book  of  Invertebrate  Zoology. 

APIS  MELLIFICA  (Honey-bee) 

The  life  of  this  form  is  so  different  from  that  of  the  grass- 
hopper that,  should  time  permit,  a  study  of  its  complete 
anatomy  would  be  profitable,  but  attention  will  here  be  con- 
fined to  a  few  of  the  more  general  adaptations  that  fit  it  for 

its  life. 

Bees  at  work  on  flowers  should  be  examined  and  the 
methods  of  getting  honey  and  pollen  noticed. 

1.  Catch  by  the  wings  a  bee  that  has  been  gorging  itself 
and  bend  the  abdomen  forward  with  your  thumbnail  until 
the  bee  disgorges.  Notice  where  the  fluid  comes  from  and  how 
much  there  is  of  it.  When  the  abdomen  is  released  watch  the 
bee  as  it  swallows  the  drop  it  has  disgorged. 

2.  Notice  where  the  pollen  is  carried,  and  see  if  you  can 
determine  how  it  is  attached.  Examine  bees  working  on  dif- 
ferent flowers,  or  watch  them  as  they  enter  their  hives,  and 
see  if  the  pollen  is  always  of  the  same  color.  Do  you  under- 
stand what  the  pollen  is  and  what  the  bees  use  it  for? 

3.  You  may  find  bees  gathering  pitch  from  buds,  knots, 
boards,  or  freshly  varnished  furniture,  and  fastening  it  on 
their  legs.    Do  you  know  what  this  is  used  for? 

4.  Watch  the  entrance  of  a  beehive  and  see  if  the  bees 
going  in  are  ever  challenged.  Perhaps  you  may  see  the 
method  of  defense.  If  so,  you  will  notice  that  the  stranger 
simply  tries  to  get  away.  You  may  also  see  how  dead  bees 
and  foreign  materials  are  removed. 

5.  It  is  desirable  to  see  something  of  the  activities  in  the 
hive.  This  can  be  most  satisfactorily  done  with  a  glass-walled 
observatory  hive,  by  means  of  which  comb-building,  honey- 


apis  207 

storing,  egg-laying,  brood-rearing,  etc.,  can  be  very  satis- 
factorily studied. 

Directions  for  the  study  of  the  mouth  parts  and  the  sting 
are  all  that  seem  necessary,  but  the  wings  should  be  exam- 
ined microscopically  to  see  how  those  of  a  side  are  joined 
together,  and  a  hind  leg  should  be  examined  to  see  how  the 
hairs  on  the  tibia  form  a  pollen  basket. 

Mouth  Parts. — 1.  With  a  lens  notice  the  pair  of  hard 
jaws,  the  mandibles,  situated  on  the  sides  of  the  head  at 
the  base  of  the  tongue.  These  mandibles  are  directly  homolo- 
gous with  the  mandibles  of  the  grasshopper.  Between  the 
bases  of  the  mandibles  is  a  labrum,  and  extending  from  be- 
neath the  end  of  the  labrum  is  a  small  epipharynx. 

2.  With  scissors  remove  the  tongue,  which  is  normally  car- 
ried against  the  lower  surface  of  the  thorax,  and  transfer  it 
to  a  watch  glass.  It  may  now  be  dehydrated,  passed  into 
oil  of  cloves,  placed  in  position  on  a  slide,  and  mounted  in 
balsam,  when  it  can  be  studied  best,  or  it  may  be  immediately 
spread  under  a  cover  or  between  slides  in  glycerin. 

3.  The   central   portion   is   the   hairy,   segmented   labium 
(the  hypopharynx  of  some  authors) ,  bearing  at  its  end  a  little 
pad  called  the  spoon.    The  labium  is  folded  lengthwise  so  as 
to  form  a  pair  of  fine  ducts  which  run  from  tip  to  base.  The 
arrangement  is  such  that  the  bee  may,  through  blood  pressure, 
unfold  the  labium.    This  probably  is  an  adaptation  for  clean- 
ing it.    Attached  to  a  median  rod,  the  mentum,  which  forms 
the  base  of  the  labium,  is  a  pair  of  flattened  appendages,  the 
labial  palps,  that  are  hinged  so  that  they  may  be  drawn  to- 
gether to  inclose  the  labium  and  thus  form  a  rather  large 
tube,  which  is  made  more  complete  by  means  of  the  remain- 
ing pair  of  flattened  appendages,  the  maxillae.    On  the  outer 
margin  of  each  maxilla  is  a  small  protuberance,  the  maxillary 
palp.     When  sipping  from  an  abundance  of  liquid  the  ex- 
temporized tube  formed  by  the  labial  palps   and  maxillae 
around  the  labium  is  used,  the   liquid  being  drawn  in   by 
means  of  the  sucking  stomach.    When  the  liquid  is  in  very 


208  ARTHROPODA 

small  quantities  it  is  apparently  lapped  up  by  the  spoon  and 
transferred  through  the  labium. 

A  figure  of  the  mouth  parts  is  desirable.1 

Sting. — The  sting  is  to  be  regarded  as  a  modified  ovipositor 
that  is  no  longer  concerned  in  depositing  eggs,  but  has  become 
a  weapon  of  offense  and  defense.  It  is  accordingly  present 
only  in  the  female.  The  queen  never  uses  her  sting  except 
on  other  queens. 

Remove  the  dorsal  integument  of  the  abdomen  of  either  a 
fresh  or  preserved  specimen,  and  find  the  dark  brown  shaft 
of  the  sting,  near  the  posterior  end.  Grasp  the  shaft  with  a 
pair  of  fine  forceps  and  forcibly  remove  it.  A  considerable 
mass  of  tissue  will  be  removed  adhering  to  the  base  of  the 
shaft,  but  this  consists  for  the  most  part  of  accessory  organs 
that  must  be  understood.  Spread  the  sting  upon  a  slide,  and 
either  dehydrate  and  mount  in  balsam,  or  mount  in  glycerin. 
The  balsam  mount  will  prove  more  satisfactory,  but  the  cover 
must  be  clamped  down  until  the  balsam  hardens. 

1.  The  shaft  consists  of  three  parts: 

(a)  A  heavy  support,  called  the  awl  or  sheath,  pointed  at 
its  extremity  and  sending  a  pair  of  arms  or  arches  from  its 
base,  which  normally  bend  ventrally,  but  are  here  forced  to 
the  sides.  At  its  extremity  each  of  these  arches  enlarges  to 
form  a  rather  large  flattened  plate,  the  sheath  plate,  to  which 
strong  muscles  are  attached. 

(b)  A  pair  of  lancets  which  are  fastened  to  the  dorsal 
surface  of  the  sheath  and  the  sheath  arches  by  tongue  and 
groove  joints  (each  tongue  is  enlarged  along  its  inner  margin 
so  that  it  is  held  firmly  in  the  groove) .  Each  lancet  is  pointed 
at  its  free  extremity,  and  its  sides  near  the  point  are  set  with 
barbs  that  point  toward  the  base  of  the  sting.  The  arch  of 
each  lancet  is  continued  past  the  end  of  the  corresponding 
sheath  arch,  and  is  there  articulated  to  one  corner  of  a  some- 
what triangular  plate.     The  remaining  corners  of  each  are 

1The  comparative  study  of  the  mouth  parts  of  a  butterfly,  horse 
fly,  house  fly,  and  mosquito  will  prove  valuable. 


apis  209 

articulated  respectively  to  the  large  sheath  plate  and  to  an- 
other plate,  the  oval  plate.  Determine  the  attachment  of  the 
muscles  to  the  plates  and  find  what  movements  of  the  lancet 
the  contraction  of  the  different  sets  of  muscles  would  cause. 
Note  that  the  lancets  are  elastic  and  bend  easily. 

The  large  muscles  attached  to  the  sheath  plates  were  at- 
tached to  the  wall  of  the  abdomen  and  function  to  give  the 
thrust  that  sets  the  sting.  After  the  sting  is  drawn  from  the 
body  of  the  bee  the  muscles  attached  to  the  plates  continue 
active,  and  the  sting  works  deeper  and  deeper  in.  Understand 
why  it  works  in  instead  of  out. 

2.  Lying  near  the  base  of  the  shaft  is  a  large  poison  sac 
or  reservoir,  which  is  very  muscular.  It  receives  its  poison 
from  the  poison  gland,  a  long  and  narrow  coiled  tube  that  is 
bifurcated  near  its  free  end.  It  discharges  the  poison  by 
means  of  the  contraction  of  the  muscles  of  its  walls  through  a 
rather  large,  short  duct  into  the  space  inclosed  by  the  sheath 
and  the  two  barbs.  Each  barb  bears  a  prominence  that 
serves  as  an  injector,  which  moves  backward  and  forward 
with  the  barb  to  which  it  is  attached,  in  an  enlargement  of 
the  basal  portion  of  the  sheath.  It  may  be  seen  in  the  prep- 
aration. In  this  way  poison  is  forced  into  the  wound.  Poison 
may  also  be  admitted  to  the  cavities  of  the  lancets,  which 
are  hollow,  and  escape  through  minute  pores  near  the  barbs. 

3.  Lying  near  the  base  of  the  shaft  of  the  sting,  some- 
times covered  by  the  poison  sac,  may  nearly  always  be  found 
the  last  pair  of  abdominal  ganglia,  from  which  nerves  may 
be  traced  to  the  muscles  that  are  attached  to  the  plates. 

Understand  the  whole  mechanism,  how  it  is  operated  and 
its  use. 

4.  Catch  a  living  bee  by  the  wings  and  press  the  end  of 
the  abdomen  against  a  piece  of  soft  leather,  such  as  a  leather- 
covered  book.  Pull  the  bee  away  and  with  a  lens  watch  the 
movements  of  the  sting,  which  will  remain  caught  in  the 
leather.  Observe  the  spasmodic  contractions  of  the  poison 
sac.    See  how  long  and  how  energetically  the  movements  are 

14 


210  ARTHROPODA 

continued  and  how  deep  the  sting  is  worked  in.  This  should 
remind  you  that  a  sting  should  be  removed  immediately,  and 
that  it  should  not  be  pulled  out,  as  grasping  the  poison  sac 
will  aid  in  injecting  the  poison,  but  scraped  off  with  a  finger- 
nail or  rubbed  off. 

A  drawing  showing  the  mechanism  of  the  sting  is  desir- 
able. 

Field:  A  Study  of  an  Ant.  Proc.  Acad.  Nat.  Sci.,  Philadelphia,  1901. 
Philips:  A  Review  of  Parthenogenesis.  Proc.  Am.  Phil.  Soc,  42,  1903. 
Root:    A,  B,  C  and  X,  Y,  Z  of  Bee  Culture. 


ECHINODERMATA 

Radially  symmetrical  animals,  with  calcareous  plates  in 
the  integument.    Water-vascular  system  always  present. 

Class  1.  Asteroidea. 

With  radiating  arms  not  sharply  defined  from 

the  central  disk.    Ambulacral  feet  in  grooves 

on  the  oral  side. 
Order  1.  Phanerozonia. 

With  large  marginal  ossicles.     (Astropecten.) 
Order  2.  Cryptozonia. 

Marginal  ossicles  inconspicuous.    (Asterias.) 

Class  2.  Ophiuroidea. 

With  slender  radiating  arms  sharply  defined 
from  the  central  disk.    No  ambulacral  grooves. 
Order  1.  Ophiurida. 

Arms  not  branched.     (Ophiura.) 
Order  2.  Euryalida. 

Arms  branched.     (Astrophyton.) 

Class  3.  Echinoidea. 

Globular,    or    somewhat    disk-shaped,    spiny 

bodies.    Shell  or  test  composed  of  close-fitting 

plates. 
Order  1.  Regularia. 

Nearly    globular    test.      Spines    rather    large. 

Mouth  and  anus  polar.     Jaws  present.     (Ar- 

bacia,  Strongylocentrotus.) 
Order  2.  Clypeastroidea. 

More  or  less  flattened  test.    Spines  very  small. 

Anus  not  polar.    Jaws  present.     (Echinarach- 

nius.) 
Order  3.  Spatangoidea. 

Somewhat  flattened  and  elongated,  bpmes 
very  small.    Neither  mouth  nor  anus  polar. 

Class  4.  Holothuroidea.  . 

Bodies  soft,  elongated  and  cylindrical.  Mouth 
and  anus  polar,  the  former  surrounded  by  a 
circlet  of  large  oral  tentacles. 

211 


212  ECHINODERMATA 

Order  1.  Elasipoda. 

Well-marked   bilateral   symmetry.    Tube   feet 

on    ventral    and    papillae    on    dorsal    surface. 

Deep  sea  only. 
Order  2.  Pedata. 

Ambulacral  feet  in  rows  or  scattered.     (Thy- 

one,  Cucumaria.) 
Order  3.  Apoda. 

Without  tube  feet.     Wormlike.     (Synaptula.) 

Class  5.  Crinoidea. 

Temporarily   or   permanently    attached   by   a 
stalk.     With    five   branching   arms    radiating 
from  a  small  disk. 
Order  1.  Neocrinoidea. 

Characters  as  above.     (Antedon,  Pentacrinus.) 

Berry :    Metamorphosis  of  Echinoderms.    Quart.  Jour.  Mic.  Sci.,  38,  1905. 
Coe:    Echinoderms  of  Connecticut.    State  Geol.  and  Nat.  Hist.  Surv., 

19,  1912. 
Grave:    Occurrence  among  Echinoderms  of  Larvae  with  Cilia  Arranged 

in  Transverse  Rings.    Biol.  Bull.,  5,  1903. 
Newman,  H.  H.:    Experimental  Analysis  of  Asymmetry  in  Starfish— 

Patiria  miniata.    Biol.  Bull.,  vol.  49. 

ASTEROIDEA 

ASTERIAS  (Starfish) 

Starfishes  are  rather  common  along  most  coasts  and  are 
among  the  worst  enemies  of  oysters,  mussels,  clams,  and  bar- 
nacles. They  occasionally  capture  fish  in  aquaria.  They 
can  generally  be  most  satisfactorily  examined  on  shallow- 
water  mussel-beds  or  on  rocks  covered  with  barnacles. 
Places  where  starfish  occur  should  be  visited,  and  the  con- 
ditions under  which  they  live  studied. 

1.  How  do  they  feed? 

2.  What  enemies  do  they  have? 

3.  How  are  their  arms  repaired  when  injured?  Do  you 
find  specimens  that  are  growing  new  tips  to  injured  arms  or 
are  such  arms  apparently  replaced?  When  an  arm  is  injured 
how  must  the  animal  proceed  to  repair  it? 

4.  Do  specimens  ever  conceal  themselves?     See  if  speci- 


ASTERIAS  213 

mens  can  be  found  with  pieces  of  grass  and  weeds  covering 
them.    Try  picking  these  pieces  off  to  see  if  they  adhere. 

5.  Do  the  animals  have  other  means  of  protection? 

Examine  a  specimen  and  notice  that: 

1.  The  surface  by  which  the  animal  clings,  the  oral  sur- 
face, is  different  from  the  other,  aboral  surface,  and  both 
surfaces  are  covered  with  short  spines.  What  is  the  use  of  the 
spines? 

2.  The  animal  consists  of  a  central  disk   and  radiating 

arms. 

3.  On  the  aboral  surface  of  the  disk,  near  the  junction  of 
the  two  arms,  is  a  small,  frequently  conspicuously  colored, 
circular  body,  the  madreporic  plate.  The  two  arms  adjacent 
to  this  plate  are  sometimes  referred  to  as  the  bivium,  and 
the  remaining  three  as  the  trivium.  The  radial  symmetry  of 
the  animal  is  disturbed  externally  only  by  the  madreporic 
plate.  Examine  this  plate  with  a  lens  and  determine  its 
structure. 

4.  Radiating  from  the  mouth  situated  on  the  oral  surface 
are  the  ambulacral  grooves,  one  on  each  arm.  In  these 
grooves  are  ambulacral  or  tube  feet.  Do  they  have  a  definite 
arrangement?  Along  the  sides  of  the  grooves  are  slender 
spines  that  differ  from  the  general  body  spines  in  being  mov- 
able. 

5.  Scrape  the  tube  feet  from  a  portion  of  an  ambulacral 
groove  of  a  dried  specimen  and  notice  the  pores  through  which 
the  feet  are  attached  to  organs  inside  the  arm.  Notice  also 
the  exposed  ambulacral  plates  and  determine  their  relation 
to  the  pores. 

Draw  figures  of  the  aboral  and  oral  surfaces  of  a  starfish, 
and  a  diagram  to  show  the  relation  of  the  ambulacral  plates 
and  pores. 

Place  a  living  starfish  in  a  dish  of  sea  water. 

1.  Study  its  method  of  locomotion.  How  are  the  tube 
feet  used?  Does  each  foot  act  independently,  or  is  there  any 
evidence  of  coordinated  movement? 


214  ECHINODERMATA 

2.  Place  the  starfish  on  its  aboral  surface  and  analyze  the 
method  of  righting. 

3.  Tear  the  starfish  quickly  from  the  substratum  upon 
which  it  is  crawling.  Are  any  of  the  feet  torn  from  the 
animal?  (See  Paine1  for  a  study  of  the  adhesive  power  of 
the  tube  feet.) 

4.  Find  the  threadlike  dermal  branchiae  projecting 
through  the  body  integument  on  the  aboral  surface.  They 
serve  as  respiratory  organs  and  probably  also  have  an  excre- 
tory function.  The  phagocytic  nature  of  the  cells  of  the 
coelomic  fluid  may  be  studied  by  simple  methods  reported  by 
Kindred.     (See  reference  below.) 

5.  Stroke  the  starfish  with  a  camel's-hair  brush  and  notice 
how  the  hairs  are  caught.  Can  you  determine  by  what  and 
how  they  are  held?  With  a  hand  lens  examine  around  the 
bases  of  the  spines,  and  see  the  arrangement  of  the  pedicel- 
lariae.  Their  function  is  obscure,  but  they  enable  the  star- 
fish to  hold  small  objects  firmly  and  they  may  be  of  service 
in  dealing  with  possible  surface  parasites. 

6.  Remove  some  of  the  pedicellariae  with  a  scalpel  and  ex- 
amine them  under  the  microscope.  Do  you  find  more  than 
one  kind? 

Draw  a  pedicellaria. 

Internal  Structure. — Make  the  dissection  under  water,  and 
in  cutting  through  the  integument  be  careful  not  to  injure  the 
underlying  soft  parts. 

With  strong  scissors  cut  through  the  aboral  body  wall  near 
the  tips  of  the  rays  of  the  trivium.  Carry  the  cuts  forward 
along  the  sides  of  the  rays  to  the  disk.  The  cavity  thus 
opened  is  the  coelom  or  body  cavity. 

Lift  up  the  integument  at  the  tip  of  each  arm  and  carefully 
snip  away  the  mesenteries  which  attach  the  organs  to  it.  Cut 
the  membranes  that  extend  into  the  disk  opposite  the  junc- 
tions of  the  arms,  and,  cutting  as  close  as  possible  to  the 

1  Paine,  V.  L.:  Adhesions  of  the  Tube-feet  in  Starfish.  Jour.  Exp. 
Zool.,  vol.  46,  No.  2,  1926. 


ASTERIAS  215 

madreporite,  but  leaving  this  in  place,  remove  the  three-rayed 
flap  of  integument  thus  freed. 

Irving,  L.:  Ciliary  Currents  in  the  Starfish.  Jour.  Exp.  Zool.,  vol.  41, 
1924. 

:  Regulation  of  the  pH  Concentration  and  Its  Relation  to  Metab- 
olism and  Respiration  in  the  Starfish.  Jour.  General  Physiology, 
November  20,  1926. 

Kindred,  J.  E.:  The  Cellular  Elements  of  the  Perivisceral  Fluid  of 
Echinoderms.    Biol.  Bull.,  vol.  46,  1924. 

Digestive  System. — In  studying  this  system  you  should 
constantly  bear  in  mind  the  peculiar  method  by  which  the 
animal  feeds,  as  the  digestive  system  is  highly  modified  to 
suit  this  method. 

1.  The  short,  cone-shaped  intestine  and  the  intestinal 
caeca  were  probably  removed  with  the  integument.  The  in- 
testine probably  does  not  function,  and  may  be  regarded  as 
a  vestige.  It  opens  near  the  center  of  the  disk,  on  the  aboral 
side,  by  a  very  minute  anus  that  is  very  hard  to  see. 

2.  The  stomach,  which  occupies  the  greater  part  of  the 
space  in  the  disk,  is  composed  of  a  small  aboral  portion,  the 
pyloric  division,  that  receives  the  ducts  from  the  hepatic 
caeca,  and  a  larger,  lobed,  cardiac  division,  into  which  the 
mouth  opens.  The  cardiac  portion  may  be  everted  through 
the  mouth,  thus  being  turned  wrong  side  out.  Five  pairs  of 
muscles,  which  draw  this  portion  of  the  stomach  back  into 
place,  may  be  seen  attached  to  the  ridges  formed  by  the  am- 
bulacral  plates  in  each  arm.  How  is  it  possible  for  the 
stomach  to  be  everted?  What  reason  is  there  for  two  divi- 
sions? 

3.  In  each  arm  is  a  pair  of  long,  glandular  organs,  the  so- 
called  hepatic  caeca.  The  ducts  of  each  pair  unite  and  join 
the  pyloric  division  of  the  stomach  by  a  common  duct.  These 
are  digestive  glands.  What  reason  is  there  for  having  ten 
enormous  digestive  glands?  Does  this  have  anything  to  do 
with  the  method  of  feeding? 

Make  a  drawing  of  the  digestive  system  of  the  disk  and 
one  arm. 


216  ECHINODERMATA 

Reproductive  System. — Turn  the  hepatic  caeca  to  one  side 
and  notice  the  ovaries  or  testes.  The  sexes  are  separate,  but 
the  organs  have  the  same  general  appearance  in  both  sexes. 
They  vary  in  size  according  to  the  season  of  the  year,  some- 
times being  so  small  that  they  are  not  easily  found,  and  again 
being  nearly  or  quite  as  large  as  the  hepatic  caeca.  With  a 
pair  of  forceps  lift  up  one  of  these  organs  and  see  where  it  is 
attached.  It  is  at  this  point  that  the  reproductive  cells  reach 
the  exterior.    How  many  gonads  are  there? 

Draw  the  gonads  into  another  arm  of  your  figure. 

Water-vascular  System.1 — 1.  Carefully  remove  the  side  of 
the  stomach  next  to  the  bivium,  being  very  careful  not  to  dis- 
turb the  stone  canal,  which  runs  from  the  madreporic  plate 
to  the  margin  of  the  membrane  around  the  mouth.  By  the 
side  of  the  stone  canal  is  a  thin  band  of  tissue  formerly  sup- 
posed to  be  a  heart.  It  is  generally  referred  to  as  the  axial 
organ  of  the  hemal  system.  See  Chadwick's  monograph  on 
Asterias  for  a  discussion  of  the  theories  concerning  the  nature 
of  the  hemal  system. 

2.  The  circular  canal,  which  is  joined  by  the  stone  canal 
at  the  outer  margin  of  the  peristomial  membrane,  follows  the 
margin  of  the  membrane  and  so  encircles  the  mouth.  Origin- 
ating from  it  at  points  very  near  the  ampullae  of  the  first 
tube  feet  are  nine  small  vesicles,  Tiedemann  bodies.  They 
are  smaller  than  the  ampullae  and  project  in  toward  the 
mouth.  The  position  where  the  tenth  Tiedemann  body  might 
be  expected,  is  taken  by  the  stone  canal. 

3.  Leaving  the  circular  canal  are  five  radial  water  tubes, 
one  for  each  arm.  These  tubes  lie  along  the  oral  surfaces  of 
the  ambulacral  plates,  and  are  accordingly  not  visible  on  the 
inside  of  the  animal.  The  position  of  the  tube  can  best  be 
understood  by  making  a  transverse  section  of  an  arm.  It  will 
then  be  seen  either  in  injected  or  uninfected  specimens,  lying 

1This  may  be  injected  in  fresh  specimens,  either  with  gelatin  or  fine 
starch  mass,  by  picking  up  one  of  the  radial  canals  with  a  hypodermic 
syringe  and  injecting  toward  the  disk. 


ASTERIAS  217 

immediately  below  the  ambulacral  plates.  In  injected  speci- 
mens it  may  be  followed  by  dissecting  from  the  oral  side, 
from  the  circular  canal  to  the  extremity  of  the  arm,  where  it 
ends  in  a  small  tentacle. 

4.  Along  the  sides  of  the  ambulacral  ridges,  within  the 
body  cavity,  are  rows  of  little  saclike  ampullae.  Determine 
their  relation  to  the  ambulacral  pores.  If  the  specimen  is 
fresh,  press  a  few  ampullae  and  see  if  the  corresponding  tube 
feet  are  affected.  Can  you  determine  their  function?  In  a 
dissection  it  is  hard  to  find  the  connecting  tubes  that  join 
the  radial  tubes  to  the  tube  feet,  but  they  can  sometimes  be 
seen  in  sections  of  arms  of  injected  specimens.  They  can 
readily  be  seen  in  microscopic  preparations. 

The  water-vascular  system  is  very  distinctive  for  the 
Echinodermata,  and  you  should  understand  perfectly: 

(a)   How  the  tube  feet  are  extended. 

(6)  What  causes  them  to  adhere. 

(c)  The  connection  between  tube  feet,  ampullae,  connect- 
ing canals,  radial  water  tubes,  circular  canal,  stone  canal,  and 
madreporic  plate. 

(d)  How  it  is  possible  to  extend  one  foot  without  extend- 
ing others. 

Make  a  drawing  showing  the  arrangement  of  the  water- 
vascular  system. 

Nervous  System. — This  is  not  easily  studied  by  dissection. 
It  consists  of  a  nerve  ring  which  encircles  the  mouth  and  lies 
just  ventral  to  the  circular  water  canal,  and  five  radial  nerves 
that  extend  down  the  arms  just  beneath  the  radial  water 
tubes,  to  end  at  the  tips  of  the  arms  in  pigment  spots,  the 
eye  spots.  The  whole  central  nervous  system  is  superficial 
and  forms  a  portion  of  the  outer  covering  of  the  body.  The 
radial  nerves  can  be  seen  by  separating  the  rows  of  ambu- 
lacral feet,  but  it  is  much  more  satisfactory  to  study  them  in 
prepared  sections. 

Muscular  System. — Examine  the  walls  of  the  starfish  for 
its  muscular  system.    If  time  permits,  it  will  be  desirable  to 


218  ECHINODERMATA 

macerate  a  portion  of  an  arm  to  see  the  skeleton  to  which 
these  muscles  are  attached. 

Study  prepared  sections  of  the  arm  of  a  small  starfish  and 
determine  the  relation  of  organs. 

1.  The  hepatic  caeca.  How  are  they  supported?  What 
is  their  structure? 

2.  The  radial  canal,  connecting  tubes,  tube  feet,  and  am- 
pullae. 

3.  The  thickened,  deeply  stained,  radial  nerve  between  the 
tube  feet  and  below  the  radial  water  tube. 

4.  The  perihemal  canal,  divided  by  a  thin  partition,  that 
lies  between  the  radial  water  tube  and  the  radial  nerve. 

Make  a  drawing  of  a  section  of  an  arm  that  will  show 
these  points. 

Understand  how  a  starfish  can  open  an  oyster  or  a  mussel 
and  how  it  digests  it  when  open.  How  can  it  digest  a  bar- 
nacle or  small  snail?    How  does  it  respire? 

Chadwick,  H.  C:    Memoir  No.  25.    Asterias.     Liverpool  Marine  Biol. 

Committee,  1923. 
Cole:   Experiments  on  Coordination  and  Righting  in  the  Starfish.    Biol. 

Bull.,  24,  1913. 
:     Direction    of   Locomotion    in   Starfish,   Asterias   forbesi.     Jour. 

Exp.  Zool.,  14,  1913. 
Field:    Larva  of  the  Asterias  vulgaris.    Quart.  Jour.  Mic.  Sci.,  34,  1892. 
Gemmill,  J.  F.:    The  Development  and  Certain  Points  in  the  Adult 

Structure  of  the  Starfish,  Asterias  rubens.     Phil.  Trans,  of  the  Roy. 

Soc,  London,  Series  B,  vol.  205,  1914. 
Hopkins,  A.  E.:   On  the  Physiology  of  the  Central  Nervous  System  in 

the  Starfish,  Asterias  tenuispina.    Jour.  Exp.  Zool.,  vol.  46,  No.  2,  1926. 
Jennings:    Behavior  of  the  Starfish  Asterias  forreri.    Univ.  Calif.  Pub. 

Zool.,  4,  1907. 
MacBride:    Development  of  Asterias  gibbosa.     Quart.  Jour.  Mic.  Sci., 

38,  1896. 
Mead:    The  Natural  History  of  the  Starfish.     Bull.  U.  S.  Fish  Com., 

1899. 
Tennent  and  Hogue:    Studies  on  the  Development  of  the  Starfish  Egg. 

Jour.  Exp.  Zool.,  3,  1906. 


ASTERIAS,    OPHIURA  219 

OPHIUROIDEA 

OPHIURA  (Serpent-star) 

These  animals  live  more  or  less  concealed  in  crevices, 
shells,  eel  grass,  etc.,  and  may  be  obtained  either  by  dredging 
or  by  pulling  a  dip  net  through  eel  grass.  They  are  not  con- 
spicuous objects  along  the  shore,  as  are  starfish,  and  they 
differ  essentially  from  starfish  in  their  method  of  locomotion 
and  their  method  of  feeding. 

Examine  a  specimen  and  notice: 

1.  The  appearance  of  the  disk  and  arms.  Are  the  spines 
similar  to  those  of  Asterias?  The  arms  are  more  flexible.  In 
what  direction  do  they  bend  easiest? 

2.  The  five  buccal  plates,  one  of  which  bears  a  madreporic 
opening  that  is  not  easily  seen. 

3.  The  size  and  shape  of  the  mouth. 

4.  The  ambulacral  grooves.    Are  they  distinct? 

5.  The  ambulacral  feet.  Do  they  have  suckers?  How 
are  they  arranged? 

6.  The  openings  to  the  bursae,  near  the  bases  of  the  arms. 
Most  ophiurans  have  five  pairs  of  these  openings,  one  for 
each  bursa,  but  Ophiura  has  ten  pairs,  two  for  each  bursa. 

Draw  an  oral  view  of  a  specimen. 

Place  a  living  specimen  in  a  dish  of  sea  water  and  watch 
its  movements. 

1.  Compare  the  rate  and  method  of  movement  with  As- 
terias. 

2.  Are  all  of  the  arms  used  in  progressing  in  the  same 

way? 

3.  See  if  the  arms  can  be  used  interchangeably  or  if  a 
certain  one  is  always  directed  forward. 

4.  Are  the  ambulacral  feet  of  any  service?  Do  they  ad- 
here? The  internal  structure  shows  that  the  stomach  is  not 
eversible  and  that  the  hepatic  caeca  do  not  extend  into  the 
arms.    Is  there  any  correlation  between  these  two  facts? 

The  nervous  and  water- vascular  systems  are  very  similar 
to  those  of  Asterias,  but  here  the  former  lies  within  instead  of 


220  ECHINODERMATA 

on  the  surface  of  the  arm,  the  entire  arm  being  encased  with 
four  or  more  rows  of  shields.  They  can  be  studied  best  in 
sections. 

Grave:    Ophiura  brevispina  I.    Mem.  Biol.  Lab.  Johns  Hopkins  Univ., 

4,  1900.    Mem.  Nat.  Acad.,  8,  1899. 
:   Ophiura  brevispina  II.   An  Embryological  Contribution  and  Study 

of  the  Effect  of  Yolk  Substance  upon  the  Developmental  Process. 

Jour.  Morph.,  27,  1916. 

ECHINOIDEA 

ARBACIA  OR  STRONGYLOCENTROTUSi  (Sea  Urchin) 

In  some  localities  sea  urchins  can  be  found  in  tide  pools 
or  near  low-tide  mark,  where  they  may  be  very  abundant. 
In  other  localities  they  can  be  obtained  only  by  dredging. 
When  possible  they  should  be  observed  in  their  native  places 
and  the  conditions  noted. 

1.  What  apparently  serves  as  food  for  the  animal?  Can 
you  determine  how  this  is  obtained? 

2.  Do  you  find  attempts  at  concealment? 

3.  Are  the  animals  able  to  climb? 

Put  a  living  sea  urchin  in  a  dish  of  sea  water  and  study 
its  movements. 

1.  When  placed  on  its  back,  how  does  it  turn  over? 

2.  What  is  the  normal  method  of  progression? 

3.  How  are  the  spines  arranged  when  the  animal  is  creep- 
ing on  the  bottom? 

4.  What  difference  do  you  note  between  the  spines  on  the 
lower  and  upper  surfaces? 

5.  How  long  are  the  tube  feet?  Are  they  used  with  the 
spines  in  moving  or  do  both  sets  of  organs  act  independently? 

6.  Grasp  a  spine  with  your  forceps  and  see  if  neighboring 
spines  respond.    Do  they  form  defensive  armor? 

7.  In  what  directions  may  a  spine  be  moved?  Remove  a 
spine  from  a  preserved  specimen  and  determine  how  it  was 
attached  and  how  the  muscles  that  moved  it  were  attached 
to  the  spine  and  to  the  test. 

Make  a  diagram  showing  the  arrangement. 

1  These  directions  will  serve  for  any  of  our  common  sea  urchins. 


ARBACIA   OR   STRONGYLOCENTROTUS  221 

8.  Do  the  spines  have  any  definite  arrangement? 

9.  By  means  of  the  lube  feet,  notice  that  there  are  five 
ambulacral   areas,   between   which   are   five   inter  ambulacra! 

areas. 

10.  Notice  an  area  on  the  aboral  surface  which  is  free 
from  spines.    This  is  the  periproct. 

11.  Notice  the  membrane  around  the  mouth,  the  peris- 
tome. 

12.  Look  for  pedicellariae  on  the  peristome.  In  what 
other  places  are  pedicellariae  found?  Do  they  differ  from 
those  of  the  starfish? 

Draw  one. 

13.  Notice  the  tentacles  (modified  tube  feet)  on  the  peris- 
tome. 

14.  The  dermal  branchiae  are  shrublike  appendages  at  the 
outer  edge  of  the  peristome.  They  are  situated  opposite  each 
interambulacral  area. 

Skeleton.1 — Examine  the  aboral  surface  of  a  cleaned 
"test." 

1.  The  periproct  has  scattered  plates  which  cover  the 
anal  opening.     (Four  triangular  ones  in  Arbacia.) 

2.  Around  these  anal  plates  are  five  large  ones,  that  form 
the  apices  of  the  interambulacral  series  of  plates.  These  are 
the  genital  plates,  and  each  is  perforated  by  a  small  opening, 
the  genital  pore. 

3.  One  of  the  genital  plates  is  larger  than  the  others  and 
is  full  of  very  minute  pores.  This  is  the  madreporite,  which 
is  homologous  with  the  madreporite  of  the  starfish.  Deter- 
mine its  structure  with  a  lens. 

4.  Between  the  genital  plates1  are  five  smaller  ocular 
plates,  also  perforated,  which  form  the  apices  of  the  ambu- 

1  If  a  preserved  specimen  of  Strongylocent'rotus  be  placed  in  a  solu- 
tion of  nitric  acid  (about  15  per  cent)  from  five  to  ten  minutes,  the 
plates  of  the  test  can  be  more  easily  seen,  especially  after  drying.  This 
is  apparently  due  to  the  coloring  matter  in  the  animal  itself.  "Arbacia 
is  not  helped  by  the  treatment. 


222  ECHINODERMATA 

lacral  series  of  plates.     These  plates  and  the  genital  plates 
together  form  what  is  known  as  the  apical  system. 

5.  In  the  ambulacral  series  of  plates,  note  the  arrangement 
of  the  openings  (ambulacral  pores)  through  which  the  tube 
feet  protrude. 

6.  Do  all  of  the  plates  bear  balls  to  which  spines  were 
articulated?  Are  the  balls  of  equal  size?  Do  they  have  a 
definite  arrangement? 

Can  you  homologize  the  positions  of  the  ambulacral,  inter- 
ambulacral,  ocular,  and  genital  plates  in  the  sea  urchin  and 
starfish?  What  portion  of  the  starfish  is  represented  by  the 
periproct  of  the  sea  urchin? 

Make  a  drawing  of  the  test,  showing  the  ambulacral,  inter- 
ambulacral,  and  apical  systems  of  plates. 

7.  Around  the  peristome,  on  the  inside  of  the  test,  note 
the  five  auricles  forming  arches  or  bridges  over  the  bases  of 
the  ambulacral  areas.    Their  purpose  will  be  seen  later. 

Cut  around  the  equatorial  region  of  an  alcoholic  specimen, 
taking  care  to  cut  through  the  test  only.  Break  the  aboral 
portion  away  bit  by  bit  with  forceps  until  near  the  genital 
plates,  freeing  the  fragments  from  the  internal  organs  with- 
out disturbing  their  positions. 

Reproductive  System. — How  were  the  gonads  (their  ap- 
pearance is  the  same  in  both  sexes)  attached  to  the  test? 
How  many  are  there?  Opposite  what  areas  of  the  test  are 
they  placed?  Where  do  they  open  to  the  exterior?  Without 
mutilating,  find  the  narrow  strip  of  tissue  that  connects  the 
gonads  to  each  other  near  their  aboral  ends.  This  is  the 
genital  rachis.  Connected  with  the  genital  rachis  and  lying 
alongside  the  stone  canal,  which  leads  from  the  madreporite, 
is  the  genital  stolon. 

Digestive  System. — Remove  the  gonads  from  the  three 
areas  farthest  from  the  madreporic  plate,  lift  the  remaining 
aboral  portion  of  the  test  slightly,  examine  the  alimentary 
canal,  and  note: 

1.  The  large  and  conspicuous  jaws,  frequently  called  the 
lantern.    They  will  be  studied  later. 


ARBACIA  OR   STRONGYLOCENTROTUS  223 

2.  The  esophagus,  passing  between  the  jaws,  and  bending 
over  to  one  side  to  join  the  intestine. 

3.  The  intestine.  Notice  its  size  and  its  shape.  Do  its 
loops  have  any  relation  to  the  positions  of  the  gonads? 

4.  The  intestinal  siphon,  lying  along  the  intestine  and 
attached  to  it  at  both  ends. 

5.  The  rectum,  running  from  the  end  of  the  intestine  to 
the  anus. 

6.  The  mesenteries  which  hold  the  various  organs  in  place. 
Make  a  drawing  to  show  the  reproductive  and  digestive 

organs. 

Water-vascular  System. — 1.  The  stone  canal  leads  from 
the  madreporite  to  the  circular  canal,  which  encircles  the 
esophagus  at  a  point  just  above  the  lantern. 

2.  From  the  circular  canal  radial  tubes  pass  over  the  top 
and  down  the  sides  of  the  lantern,  to  pass  through  the  auricles 
and  up  the  ambulacral  tracts,  to  the  ocular  plates.  They  can 
easily  be  seen  along  the  sides  of  the  test,  but  are  difficult  to 
see  before  they  leave  the  lantern. 

3.  Along  the  course  of  each  radial  canal,  the  ampullae, 
which  supply  the  tube  feet,  are  to  be  seen.  The  relations  of 
the  tube  feet  and  radial  canals  are  practically  the  same  as  in 
the  starfish  except  that  the  removal  of  the  radial  tubes  to  the 
inner  sides  of  the  ambulacral  plates  causes  two  perforations 
for  each  foot  here,  while  the  starfish  has  only  one.  One  of 
these  perforations  is  for  the  connection  between  the  ampulla 
an»d  the  foot,  the  other  is  for  the  connecting  tube  between 
the  radial  canal  and  the  foot.  The  connecting  tube  joins 
the  foot  outside  of  the  plates  (as  in  the  starfish),  while  it 
joins  the  radial  canal  inside  of  the  plates  (different  from  the 
starfish) . 

Remove  the  intestine  and  study  the  lantern  and  its  at- 
tachments. 

1.  The  whole  lantern  is  inclosed  in  a  delicate  membrane, 
the  peripharyngeal  or  lantern  membrane  which  contains  the 


224  ECHINODERMATA 

lantern  coelom.  This  space  communicates  with  the  five  radial 
perihemal  canals,  which  run  along  the  ambulacral  areas  be- 
tween the  radial  canals  and  radial  nerves,  and  with  the  der- 
mal branchiae.     It  is  important  in  respiration. 

2.  The  tip  of  the  lantern  is  attached  to  the  flexible  per- 
istoma, and  muscles  extending  from  various  parts  of  it  are 
attached  to  the  hard  parts  of  the  surrounding  test. 

In  shape  the  lantern  is  a  five-sided,  radially  symmetrical 
pyramid.  Each  of  the  sides  consists  of  a  massive  calcareous 
structure,  the  alveolus,  which  supports  an  elongated  tooth  the 
tip  of  which  projects  through  the  peristome.  The  base  of 
the  pyramid  may  be  compared  with  a  wheel,  in  which  the  ten 
epiphyses,1  two  of  which  are  attached  to  each  alveolus,  are 
the  tire,  and  the  five  radially  directed  rotulae  are  the  spokes. 
Each  rotula  has  a  more  slender  bar,  forked  at  the  free  ex- 
tremity, the  compass  or  radius,  lying  over  it.  Each  of  the 
five  segments  represents  a  jaw  that  is  articulated  to  its 
neighbors  at  its  base,  near  the  esophagus.  The  points  of 
the  teeth  can  thus  be  separated  and  closed,  and  the  jaws 
protruded  and  retracted  by  means  of  muscles. 

3.  Connecting  adjacent  alveoli  from  top  to  bottom  are  the 
commutator  muscles,  that  by  their  combined  action  close  the 
jaws. 

4.  To  each  of  the  arms  of  the  radius  fork  a  muscle  is 
attached.    Where  is  it  attached  at  the  other  end? 

5.  A  pair  of  protractor  muscles  pass  down  from  each  epi- 
physis. To  what  are  they  attached?  They  are  used  in  pro- 
truding the  jaws. 

6.  A  pair  of  retractor  muscles  is  attached  to  the  tip  of 
each  alveolus.  They  can  be  used  in  opening  the  jaws  or  in 
retracting  the  jaws.    Do  you  see  how? 

7.  There  are  also  internal  and  external  rotula  muscles 
that  connect  the  epiphyses  with  the  rotulae.  Their  contrac- 
tion moves  these  plates  upon  one  another  and  thus  causes 
a  rocking  motion  of  the  jaws. 

1In  Arbacia  the  epiphyses  form  small  hooks  that  do  not  unite 
across  the  base  of  an  alveolus. 


ARBACIA   OR   STRONGYLOCENTROTUS  225 

Understand  how  the  jaws  may  be  protruded,  opened, 
closed,  and  retracted  by  means  of  these  muscles. 

8.  The  compasses  are  attached  one  to  the  other  by  the 
elevator  muscles.  Their  contraction  elevates  all  of  the  com- 
passes and  thus  enlarges  the  lantern  coelom. 

9.  Attached  to  the  forked  end  of  each  compass  is  a  pair 
of  depressor  muscles.  By  their  contraction  the  lantern 
coelom  is  compressed. 

Understand  the  action  of  this  mechanism  in  respiration. 
(See  Von  Uexhull  or  the  Cambridge  Natural  History,  Echino- 
derms,  p.  527.) 

Make  a  drawing  to  illustrate  the  arrangement  of  the  mus- 
cles. 

10.  Remove  the  lantern  by  cutting  the  peristome,  clear 
away  the  external  tissues,  and  examine  the  construction  of 
the  lantern.  With  a  scalpel  cut  the  interalveolar  muscles  so 
the  jaws  may  be  separated.     Find: 

(a)  The  large  V-shaped  alveoli  (a  straight  suture  in- 
dicates that  each  is  formed  by  the  fusion  of  two  parts). 
Notice  the  roughenings  on  their  esophageal  sides.  What  pur- 
pose can  they  serve?  Why  should  the  alveoli  be  so  large 
and  the  interalveolar  (comminator)  muscles  be  so  strong? 

(6)  The  epiphyses,  which  are  fused  with  the  upper  corners 
of  each  alveolus  and  extend  in  to  form  a  bar  over  its  base, 
thus  being  functionally  a  part  of  the  alveolus  itself.  The 
sutures  between  them  and  the  alveolus  proper  can  usually  be 
seen. 

(c)  The  rotulae,  one  of  which  joins  the  ends  of  each  ep- 
iphysis and  extends  to  the  position  of  the  esophagus.  The 
five  rotulae  of  the  lantern  articulate  with  each  other  around 
the  esophagus,  and  each  rotula  articulates  with  the  epiphyses 
of  two  adjacent  jaws.  Do  you  understand  how  the  jaws  move 
on  the  rotulae? 

(d)  The  compasses,  lying  over  the  rotulae,  are  slender  and 
bifurcated  at  their  outer  ends. 

(e)  The  teeth,  one  enclosed  in  each  alveolus.     Examine 
15 


226  ECHINODERMATA 

both  extremities  of  a  tooth  and  determine  why  the  inner  end 

is  soft. 

Understand  thoroughly  how  the  jaws  are  used  and  why 
the  animal  needs  them.  Why  does  the  sea  urchin  not  need 
large  hepatic  caeca? 

Gemmill,  J.  F.:  The  Locomotor  Function  of  the  Lantern  in  Echinus 
with  Observations  of  the  Allied  Lantern  Activities.  Proc.  Roy.  Soc, 
London,  vol.  No.  85,  1912. 

The  Nervous  System. — The  nervous  system  is  difficult  to 
demonstrate  in  dissections,  but  is  easy  to  trace  in  sections. 
It  consists  of: 

1.  A  nerve  ring  that  encircles  the  esophagus  at  a  point 
just  above  the  mouth. 

2.  Five  radial  nerves  that  pass  from  the  ring,  along  the 
insides  of  the  ambulacral  areas  of  the  test,  to  the  ocular 

plates. 

The  radial  water  tubes  will  be  found  in  sections  adjacent 
to  the  radial  nerves.  The  two  are  separated  only  by  a  nar- 
row space,  the  pseudohemal  canal.  Between  the  radial 
nerves  and  the  tissue  of  the  test  there  is  another  narrow 
cavity,  the  epineural  sinus. 

If  time  permits,  students  will  find  a  dissection  of  the  sand 
dollar,  Echinarachnius,  valuable  for  purposes  of  comparison. 
Special  notes  will  not  be  necessary.  Its  shape  and  restricted 
ambulacral  areas  should  be  studied  in  the  light  of  its  habits 
and  food  supply.    How  does  the  animal  move? 

Chadwick,  H.  C:    Memoir  No.  3,  Echinus.     Liverpool  Marine  Biol. 

Committee,  1900. 
MacBride:    Cambridge  Natural  History,  Echinodermata. 
Tennent:    Variation  in  Echinoid  Plutei.    Jour.  Exp.  Zool.,  9,  1910. 
von  Uexhull:    Die  Physiologie  des  Seeigelstachels.     Zeit.  f.  Biol.,  39. 
:    TJeber  die  Function  der  Polischen  Blasen  am  Kauapparat  der 

regularen  Seeigel.    Mitth.  Zool.  Stat.  Neapel,  12,  1897. 

HOLOTHUROIDEA 

THYONE  (Sea  Cucumber) 

These  animals  may  be  found  in  protected  and  usually 
muddy  places,  concealed  in  eel  grass.     They  are  generally 


ARBACIA   OR    STRONGYLOCENTROTUS,   THYONE  227 

so  well  concealed  that  they  cannot  be  satisfactorily  studied 
in  their  native  places.  It  is  desirable  to  visit  places  where 
they  occur  and  to  observe  the  parts  visible  above  the  mud. 
It  is  then  possible  to  realize  the  life  for  which  they  are 

adapted. 

Examine  a  living  expanded  specimen  in  an  aquarium 
(taking  care  not  to  disturb  it)   and  note: 

1.  How  the  tentacles  are  used.  What  kind  of  food  would 
it  get  by  this  means?  Compare  the  method  of  food-getting 
with  the  starfish  and  sea  urchin.  How  many  tentacles? 
Arrangement?  To  what  structures  in  the  sea  urchin  do  they 
probably  correspond? 

2.  The  respiratory  movements  of  the  body.  Notice  the 
strength  of  the  current  of  water  ejected. 

3.  The  general  shape  of  the  body  when  expanded.  Does 
it  seem  to  rest  on  a  particular  side? 

Kill  the  specimen  by  catching  it  with  strong  forceps  be- 
hind the  mouth,  when  the  tentacles  are  expanded,  and  holding 
it  in  hot  water.1    Note  that: 

1.  The  body  is  covered  with  papilliform  ambulacral  feet. 
It  is  possible  in  some  cases  to  see  that  they  are  arranged  in 
five  broad,  longitudinal  bands. 

2.  The  suckers  are  less  abundant  on  the  dorsal  (upper) 
surface  than  on  the  ventral. 

3.  A  small  papilla  is  to  be  found  on  the  dorsal  surface, 
between  the  tentacles.  On  it  is  the  genital  opening.  This 
will  be  referred  to  again. 

Make  a  drawing  of  the  animal  as  seen  from  the  side,  in- 
dicating all  of  the  points  of  structure  that  have  been  seen. 

With  a  pair  of  scissors,  open  the  animal  longitudinally 
along  the  middle  of  the  ventral  (lower)  surface. 

Digestive    System. — Note:     1.    The    delicate,    perforated 

mesentery,  which  attaches  digestive  tract  to  body  wall. 

1  Specimens  that  do  not  expand  may  be  injected  with  a  saturated 
solution  of  chloretone  (saturated  by  heating).  After  the  animal  re- 
laxes the  tentacles  may  be  pushed  out.  Then  kill  in  hot  water  or  dis- 
sect immediately. 


228  ECHINODERMATA 

2.  The  esophagus,  leading  from  the  mouth  through  a  cal- 
careous structure,  which  recalls  the  lantern  of  the  sea  urchin. 
Examine  and  see  if  the  arrangement  is  similar  to  that  of  the 
sea  urchin  lantern.  The  muscles  for  the  retraction  of  the 
lantern  are  frequently  torn  from  their  attachments  at  one 
end. 

3.  The  thin-walled  and  enlarged  stomach. 

4.  The  coiled  intestine,  which  leads  to  the  cloaca. 
Draw  the  alimentary  canal  in  'position. 

Cut  the  alimentary  canal  just  in  front  of  the  stomach, 
and  close  to  the  cloaca,  and  as  you  remove  it  notice  the 
blood  vessel  that  runs  along  the  intestine. 

Respiratory  and  Excretory  System. — Arising  laterally 
from  either  side  of  the  cloaca  are  the  two  respiratory  trees. 
They  are  branched  and  project  far  forward  into  the  body 
cavity.  Can  you  determine  how  they  are  filled  with  water 
and  how  the  matter  is  expelled?  With  a  pipette  inject  them 
with  starch  mass.  The  strong  jets  of  water  ejected  by  the 
living  specimen  were  thrown  from  these  tubes.  Can  you 
understand  how  they  serve  for  respiration?  The  walls  of 
the  tubes  composing  the  trees  are  glandular  and  may  thus 
serve  to  excrete  wastes.  Notice  the  muscles  that  radiate 
from  the  walls  of  the  cloaca  to  the  body  wall.  What  is  their 
function? 

Make  a  drawing  of  the  cloaca  and  respiratory  trees. 

Reproductive  System. — The  single  gonad  (ovary  or  tes- 
tis) occupies  a  median  dorsal  position  in  the  anterior  part  of 
the  body  cavity.  It  is  composed  of  a  multitude  of  filaments, 
which  join  to  make  a  brush.  This  brush  projects  backward 
into  the  body  cavity.  The  duct  of  the  organ  lies  along  the 
dorsal  midline,  between  the  right  and  left  dorsal  muscle 
bands,  and  leads  to  the  opening  upon  the  small  papilla  near 
the  mouth  that  has  already  been  noticed. 

Water-vascular  System. — 1.  The  circular  canal  can  be 
found  in  favorable  specimens,  surrounding  the  deeper  portions 
of  the  esophagus.  It  gives  rise  to  one  or  two  Polian  vesicles, 
which  are  very  large  and  hang  down  into  the  body  cavity. 


THYONE  229 

2.  The  five  radial  canals  (homologous  with  the  radial 
canals  of  the  starfish  and  sea  urchin)  originate  from  the  cir- 
cular canal,  pass  forward  and  then  backward,  and  end  near 
the  cloaca.  The  radial  canals  take  the  general  course  of  the 
longitudinal  muscle  bands  and  lie  between  this  muscle  band 
and  the  body  wall.  The  radial  canal  may  be  seen  if  the 
muscle  band  is  carefully  removed. 

3.  Ten  forwardly  directed  canals,  the  tentacular  canals, 
leave  the  radial  canals  near  the  circular  canal  and  pass  into 
the  tentacles,  which  may  be  homologized  with  tube  feet. 

4.  The  stone  canal  and  madreporite  are  much  reduced  in 
holothurians.  The  madreporite,  except  in  larvae  and  very 
young  specimens,  is  not  found  on  the  outer  surface.  The 
stone  canal  leads  obliquely  backward  from  the  circular  canal, 
toward  the  dorsal  body  wall,  to  join  a  small  calcareous  body, 
the  madreporite,  which  lies  in  the  body  cavity  and  is  not 
perforated.  Does  this  give  you  a  reason  for  the  presence  of 
large  Polian  vesicles?  The  liquid  in  the  water- vascular  sys- 
tem is  not  sea  water.  Notice  its  color.  Are  there  cells  in 
it?     Examine  under  microscope. 

Make  a  diagram  of  the  water-vascular  system. 

Muscular  System. — Besides  the  special  muscles  radiating 
from  the  cloaca  which  have  been  referred  to  in  connection 
with  the  respiratory  system,  and  the  muscles  of  the  lantern, 
there  are  five  strong  longitudinal  bands,  really  pairs.  In 
which  areas  do  they  lie?  What  function  do  they  perform? 
Look  for  smaller  circular  bands.  Are  there  many  of  them? 
What  is  their  function?  Can  you  explain  the  varied  worm- 
like motions  of  the  body  by  the  action  of  these  muscles? 

Nervous  System. — This  cannot  be  satisfactorily  studied  in 
dissections.  There  are  five  radial  nerves  and  a  circular  ring. 
The  nerves  are  embedded  in  the  body  wall  and  are  hard  to 
find 

The  classes  of  the  Echinodermata  show  exceptionally  well 
how  a  general  type  of  structure  may  be  retained  and  still 


230  ECHINODERMATA 

modified  in  certain  regards  for  special  habits.  Compare,  for 
instance,  the  feeding  habits  of  the  starfish,  sea  urchin,  and 
sea  cucumber. 

Crozier,  W.  J.:  The  Orientation  of  a  Holothurian  by  Light.  Am.  Jour. 
Physiology,  vol.  37,  1921. 

Kille,  F.  R.:  Regeneration  in  Thyone  briareus  Lesueur  following  in- 
duced autotomy.     Biol.  Bull.,  69,  1935. 

van  der  Heyde:  Hemoglobin  in  Thyone  briareus  lesueur.  Biol.  Bull., 
vol.  42,  1922. 


CHORDATA 

Bilaterally  symmetrical  coelomate  animals  with  a  noto- 
chord, dorsal  and  tubular  central  nervous  system,  and  a 
pharynx  perforated  by  branchial  clefts   (gill  slits). 

Subphylum  1.  Protochordata. 
Class  1.  Hemichorda. 

The  notochord  is  poorly  developed  and  re- 
stricted to  the  anterior  end  of  the  body. 

Order  1.  Enteropneusta. 

Wormlike,  with  numerous  branchial  clefts,  a 
straight  intestine,  and  a  terminal  anus.  Body 
divided  into  three  regions — proboscis,  collar, 
and  trunk.  Development  usually  with  a  met- 
amorphosis, the  larva  being  known  as  a 
tornaria.     (Balanoglossus  and  Dolichoglossus.) 

Order  2.  Pterobranchia. 

Tubicolous,  with  one  pair  of  branchial  clefts  or 
none,  a  U-shaped  alimentary  canal,  and  a  dor- 
sal anus  situated  near  the  mouth.  Proboscis 
flattened  ventrally  into  a  large  "buccal  disk," 
its  base  covered  dorsally  by  the  collar  which  is 
produced  into  two  or  more  tentaculiferous 
arms.  Trunk  short,  prolonged  into  a  stalk. 
Reproduction  by  budding  occurs.  (Cephalo- 
discus,  Rhabdopleura.) 

Order  3.  Phoronidea  (doubtfully  placed  with  the  chor- 
dates) . 
Tubicolous  with  gregarious  habits.  The  body 
ends  in  a  plume  of  ciliated  tentacles ;  the 
alimentary  canal  is  U-shaped.  There  is  a 
larva  known  as  actinotrocha.  (Phoronis.) 
Class  2.  Urochorda. 

The  adult  body  is  enclosed  in  a  tunic  or  test, 
and  usually  lacks  a  notochord;  the  central 
nervous  system  is  reduced  to  a  simple  ganglion. 
With  an  atrial  cavity  and  a  pharynx  perfor- 
ated by  from  two  to  many  gill  clefts.  There 
is  usually  a  tadpole-shaped  motile  larva  which 
possesses  a  tubular  dorsal  central  nervous  sys- 
tem and  a  notochord  restricted  to  the  caudal 
region. 

231 


232 


CHORDATA 


Order  1.  Larvacea. 

Small  pelagic  tunicates  swimming  throughout 
life  by  means  of  a  tail.  With  a  persistent 
notochord  and  a  single  pair  of  gill  slits.  (Ap- 
pendicularia,  Oikopleura.) 

Order  2.  Ascidiacea. 

Mostly  fixed,  solitary  or  colonial  tunicates, 
which  in  the  adult  are  never  provided  with  a 
tail  and  have  no  trace  of  a  notochord.  The 
test  is  well  developed,  the  pharynx  large  and 
perforated  by  many  gill  slits.  In  most  ascidi- 
ans  the  sexually  produced  embryo  develops 
into  a  tailed  larva;  many  ascidians  reproduce 
by  budding  to  form  colonies.  (Ciona,  Mol- 
gula,  Styela,  Perophora,  Botryllus,  Ama- 
roucium,  Leptoclinum.) 

Order  3.  Thaliacea. 

Pelagic  tunicates  which  swim  by  forming  cur- 
rents in  the  water.  The  adult  is  never  pro- 
vided with  a  tail  or  a  notochord.  The  phar- 
ynx has  two  or  more  gill  slits.  Alternation  of 
generations  occurs,  and  may  be  complicated 
by  polymorphism.  (Salpa,  Doliolum.) 
Class  3.  Cephalochorda. 

The  notochord  extends  the  entire  length  of  the 
body  including  the  head.    The  body  is  meta- 
merically  segmented.     (Amphioxus.) 
Subphylum  2.  Vertebrata. 

A  brain  is  developed  as  an  enlargement  of  the 
anterior  end  of  the  central  nervous  system ;  the 
notochord  extends  no  further  forward  than  the 
middle  of  the  brain,  and  a  vertebral  column 
and  cranium  are  present.  (Cyclostomes,  fishes, 
amphibians,  reptiles,  birds,  mammals.) 

Conklin:    Organization  and  Cell  Lineage  of  the  Ascidian  Egg.     Jour. 

Acad.  Nat.  Sci.,  Philadelphia,  2nd  Ser.,  13,  1905. 
:    Does  Half  of  an  Ascidian  Egg  Give  Rise  to  a  Whole  Larva? 

Arch.  f.  Entwicklungsm.  d.  Org.,  21,  1906. 
Metcalf:    Notes  on  the  Morphology  of  the  Tunicata.    Zool.  Jahrb.,  13, 

1900. 


dolichoglossus   (balanoglossus)  233 

ENTEROPNEUSTA 

DOLICHOGLOSSUS  (BALANOGLOSSUS)  KOWALEVSKII 

In  the  natural  habitat,  note  the  character  of  the  bottom 
where  Dolichoglossus  is  found.  Is  the  sand  clean  or  is  here 
an  admixture  of  organic  material?  Note  the  frail  tube  of 
sand  particles  fastened  together  with  mucus,  and  the  numer- 
ous "castings."  The  animal  has  a  characteristic  and  un- 
pleasant odor. 

Note  the  division  of  the  body  into  three  general  regions: 
(1)  a  yellowish-white  conical  proboscis;  (2)  the  collar,  which 
is  brilliant  orange-red,  especially  in  males,  with  a  white  ring 
posteriorly;  and  (3)  the  trunk,  which  is  mainly  orange- 
yellow,  shading  to  a  greenish-yellow  in  the  transparent  pos- 
terior region,  which  is  often  broken  off  when  the  animal  is 
collected. 

The  trunk  may  be  divided  into  the  following  regions, 
which  overlap:  (a)  an  anterior  branchial  region,  bearing  on 
each  side  not  far  from  the  dorsal  median  line  a  row  of  trans- 
verse gill  slits;  (b)  a  genital  region,  bearing  on  each  side  of 
the  body  an  irregular  and  broken  fold  or  ridge  containing  the 
reproductive  organs,  which  are  gray  in  the  female  and  yellow 
in  the  male;  (c)  a  posterior  abdominal  region,  of  much 
smaller  diameter  than  the  rest  of  the  body. 

The  mouth  is  situated  on  the  ventral  side  at  the  base  of 
the  proboscis,  and  is  concealed  by  the  free  anterior  edge  of 
the  collar.  The  animal  is  unable  to  close  its  mouth,  and  in 
burrowing  a  continuous  stream  of  sand  passes  through  the 
alimentary  canal,  forming  the  "castings"  which  are  abundant 
in  the  natural  habitat  of  the  animal.  What  must  be  the  na- 
ture of  its  food? 

Burrowing  is  effected  partly  by  muscular  contractions  of 
the  body  wall,  but  mainly  through  the  power  of  the  proboscis 
and  collar  to  become  turgid.  In  burrowing  and  feeding,  of 
what  use  to  the  animal  is  the  collar? 

Note  the  characteristic  coiling  of  the  genital  region  in 
this  species.     The  anterior  end,  including  the  branchial  re- 


234  CHORDATA 

gion,  is  normally  maintained  in  a  vertical  position.  The 
posterior  end  is  also  kept  upright,  and  can  be  moved  up  and 
down  in  a  vertical  shaft  opening  on  the  surface,  thus  en- 
abling the  animal  to  eject  the  residue  of  sand  from  the  anus. 
For  the  internal  anatomy,  the  account  in  the  Cambridge 
Natural  History  may  be  consulted.  Important  chordate 
characters  are  the  notochord,  the  dorsal  central  nervous  sys- 
tem, and  the  branchial  clefts. 

Agassiz:    The  History   of   Balanoglossus   and  Tornaria.     Amer.  Acad. 

Arts  and  Sci.,  9,  1873. 
Bateson:    The  Early  Stages  of  Balanoglossus.     Quart.  Jour.  Mic.  Sci., 

24,  1884. 
:    The  Late  Stages  of  the  Development  of  Balanoglossus.     Quart. 

Jour.  Mic.  Sci.,  25,  1885. 
Morgan:    The  Growth  and  Metamorphosis  of  Tomaria.    Jour.  Morph., 

5,  1891. 

■ :    The  Development  of  Balanoglossus.    Jour.  Morph.,  9,  1894. 

Ritter  and  Davis:    Studies  on  the  Ecology,  Morphology  and  Speciology 

of  the  Young   of  Some  Enteropneusta  of   Western  North  America. 

Univ.  Calif.  Pub.  Zool.,  1,  1904. 

UROCHORDA 

MOLGULA  MANHATTENSIS 

Specimens  of  this  simple  ascidian  may  be  found  attached 
to  old  piles,  associated  with  many  other  forms.  In  some 
localities  they  may  be  so  abundant  as  practically  to  incrust 
the  piles,  and  crowd  each  other  out  of  shape.  Examine  such 
a  mass  and  see  how  different  sized  individuals  are  associated. 
Pull  them  apart  and  see  if  there  is  any  tissue  connection  be- 
tween them  that  would  indicate  a  definite  relation  between 
neighbors.  Do  you  understand  how  the  individuals  get 
started  in  the  places  where  they  are  attached?  With  a  glass- 
bottomed  pail  you  can  see  the  expanded  individuals  on  the 
piles,  but  they  can  be  more  satisfactorily  studied  in  small 
dishes  of  sea  water. 

1.  Observe  the  contraction  and  closure  of  the  two  siphons 
when  the  animal  is  irritated. 

2.  Add  a  little  powdered  carmine  to  the  water  to  deter- 
mine which  is  the  incurrent  or  oral  and  which  is  the  excur- 
rent  or  atrial  siphon. 


MOLGULA  235 

3.  Ascertain  the  number  of  lobes  at  the  extremity  of  each 
siphon.    Are  pigment  spots  present  on  the  siphonal  lobes? 

Certain  organs  are  distinguishable  through  the  tough  tunic 
which  incloses  the  body.  The  endostyle,  a  ciliated  groove 
looking  like  a  white  thread  along  the  midventral  line  of  the 
pharynx  or  branchial  basket,  will  serve  as  a  guide  in  orient- 
ing the  animal.  Determine  dorsal,  ventral,  anterior,  posterior, 
right,  and  left  aspects. 

Make  a  drawing  of  an  expanded  animal. 

4.  The  tunic  or  test  can  be  removed  by  cutting  through  it 
with  scissors,  taking  care  not  to  injure  the  mantle  or  body 
wall.  Enlarge  the  opening  made  in  the  tunic  and  strip  it 
from  the  body.  Where  is  the  tunic  most  firmly  attached? 
Examine  a  small  piece  of  the  tunic  microscopically.  Are 
blood  vessels  visible  in  it?    Does  it  contain  any  cells? 

5.  For  further  study  use  both  fresh  and  preserved  material 
from  which  the  tunic  has  been  removed.  Identify  as  many 
organs  as  possible  through  the  mantle.  In  a  living  specimen 
note  the  beating  of  the  heart  (the  heart  is  on  the  right  side) 
and  the  frequent  reversal  of  the  direction  of  the  pulsations. 
The  endostyle,  longitudinal  pharyngeal  folds,  intestine,  gon- 
ads, gonoducts,  renal  organ,  and  subneural  glands  are  also 
visible  through  the  mantle. 

6.  Note  the  muscle  bands  of  the  mantle  which  serve  to 
contract  the  body  and  especially  the  siphons.  Where  are 
the  muscles  best  developed?  Is  there  any  definite  arrange- 
ment of  the  muscle  bands? 


Fix  a  large  specimen  by  pins  through  the  siphons,  and 
with  scissors  and  fine  forceps  remove  a  large  section  of  the 
mantle  from  the  left  side,  between  the  digestive  tract  and 
the  siphons,  injuring  the  underlying  pharynx  as  little  as  pos- 
sible. The  large  space  between  the  pharynx  and  the  mantle, 
laterally  and  dorsally,  is  the  atrium,  or  peribranchial  cham- 
ber, which  is  formed  as  an  ectodermal  involution.    Into  this 


236  CHORDATA 

atrial  cavity  open  the  intestine  and  the  gonoducts,  and  also 
the  numerous  stigmata  of  the  pharynx.  Ventrally  the 
pharynx  is  fused  with  the  mantle  in  the  region  of  the  endo- 
style. 

1.  On  each  side  of  the  upper  part  of  the  pharynx  six 
longitudinal  pharyngeal  folds  will  be  seen. 

2.  The  endostyle  is  a  ciliated  groove  along  the  midventral 
wall  of  the  pharynx.  In  a  very  fresh  specimen,  cut  out  a 
large  piece  of  the  ventral  and  left  lateral  wall  of  the  pharynx, 
preferably  near  the  siphon,  mount  it  inside  up  in  sea  water 
and  examine  with  a  microscope.  Note  the  structure  of  the 
endostyle.  At  some  distance  from  the  endostyle,  on  each  side 
of  it,  note  the  meshwork  of  blood  vessels,  and  the  curved 
openings  or  stigmata  lined  with  cilia.  Of  what  use  are  the 
cilia? 

3.  Anteriorly  the  endostyle  is  continuous  with  the  peri- 
pharyngeal ciliated  bands,  which  encircle  the  oral  end  of  the 
pharynx.  From  the  point  where  they  unite  dorsally  the 
dorsal  lamina  extends  backward  along  the  mid-dorsal  line  of 
the  pharynx.  At  its  posterior  end  will  be  seen  the  small 
opening  into  the  esophagus. 

Do  you  understand  how  the  animal  captures  its  food  and 
how  the  endostyle,  peripharyngeal  bands,  and  dorsal  lamina 
are  used? 

4.  In  front  of  the  anterior  end  of  the  dorsal  lamina  note 
the  small,  volute-shaped  dorsal  tubercle.  This  is  the  ex- 
tremity of  the  hypophysis,  a  tuhe  connecting  the  subneural 
gland  with  the  oral  cavity. 

5.  A  ring  of  oral  tentacles  will  be  seen  in  the  mouth,  an- 
terior to  the  peripharyngeal  bands.  Of  what  use  are  ten- 
tacles in  the  mouth?    How  many  tentacles  are  there? 

6.  The  very  short  esophagus  opens  into  the  stomach, 
which  will  be  recognized  by  the  brown  digestive  glands  that 
cover  it.  From  the  stomach  the  intestine  forms  a  loop  on 
the  left  side,  and  is  easily  traced  to  the  anus,  which  opens 
dorsal  to  the  pharynx  in  the  atrial  chamber.    A  longitudinal 


MOLGULA  237 

fold,  the  typhlosole,  extends  throughout  the  intestine.  What 
is  the  use  of  such  a  fold? 

Reproductive  System. — On  each  side  of  the  body,  adherent 
to  the  inside  of  the  mantle,  is  an  elongate  hermaphrodite 
gland.  Each  gland  consists  of  a  lighter  part,  the  testis,  and 
a  darker  part,  the  ovary.  The  gonoducts  open  on  the  outer 
wall  of  the  atrial  cavity  near  the  base  of  the  atrial  siphon. 
Each  consists  of  two  ducts,  oviduct  and  vas  deferens.  Micro- 
scopic examination  of  the  oviduct  may  show  the  presence  of 
eggs. 

Excretory  System. — The  renal  organ  is  a  conspicuous, 
elongated  sac  on  the  right  side.  It  contains  a  brownish  fluid 
and  usually  some  solid  matter.    It  does  not  possess  a  duct. 

Nervous  System. — The  cerebral  ganglion,  which  in  Mol- 
gula  is  almost  completely  surrounded  by  the  subneural  gland, 
lies  close  to  the  mantle,  between  the  two  siphons,  and  is  thus 
dorsal  to  the  mouth.  Nerves  can  be  seen  passing  from  the 
ganglion  to  the  two  siphons.  The  hypophysis,  a  tube  leading 
from  the  subneural  gland,  opens  as  the  dorsal  tubercle  men- 
tioned earlier. 

Circulatory  System. — 1.  The  heart,  which  lies  on  the  right 
side  between  the  hermaphrodite  gland  and  the  renal  organ, 
is  inclosed  within  a  pericardium  which  is  a  portion  of  the 
coelom.  It  should  be  studied  in  a  living  specimen,  with  the 
aid  of  a  hand  lens. 

2.  If  a  very  small  Molgula  (%  of  an  inch  in  length)  is 
studied  alive  in  a  watch  glass  with  the  microscope,  the  course 
of  the  circulation,  and  the  frequent  reversal  of  its  direction, 
can  be  observed. 

3.  From  the  dorsal  end  of  the  heart,  a  cardiovisceral 
vessel  runs  to  the  visceral  mass,  where  it  divides  into  smaller 
vessels.  These,  reuniting,  form  the  viscerobranchial  vessel 
which  extends  along  the  dorsal  surface  of  the  pharynx  above 
the  dorsal  lamina.  Numerous  small  branchial  vessels  in  the 
pharyngeal  wall  connect  this  vessel  with  the  branchio- 
cardiac,  which  lies  ventral  to  the  endostyle  and  unites  with 


238  CHORDATA 

the  ventral  end  of  the  heart.  The  frequent  reversal  of  the 
current  can  be  readily  seen  both  in  the  heart  and  in  the  ves- 
sels. 

The  relation  of  the  parts  will  be  more  clearly  understood 
if  a  second  large  specimen  is  dissected  as  follows:  with 
scissors  cut  off  the  atrial  siphon,  thus  exposing  the  atrium; 
then  similarly  remove  by  a  single  cut  the  oral  siphon,  to- 
gether with  the  anterior  end  of  the  pharynx  (the  piece  thus 
cut  off  should  contain  the  ganglion,  dorsal  tubercle,  peri- 
pharyngeal bands,  oral  tentacles,  anterior  portion  of  the  en- 
dostyle,  dorsal  lamina,  etc.). 

Make  drawings  that  will  show  the  structure. 

Hunter:    Notes  on  the  Heart  Action  of  Molgula  manhattensis.     Am. 

Jour.  Physiol.,  10,  1903. 
Kingsley:    Some  Points  in  the  Development  of  Molgula.     Proc.  Roy. 

Soc.  Nat.  Hist.,  21,  1883. 
van  Name:    Simple  Ascidians.     Proc.  Bost.  Soc.  Nat.  Hist.,  34,  1912, 

PEROPHORA 

This  ascidian  occurs  on  piles  and  other  submerged  mate- 
rials, and  is  commonly  attached  by  branching  stolons  to 
seaweeds,  simple  tunicates,  or  other  sessile  animals.  Material 
should  be  quite  fresh  for  satisfactory  study,  and  should  be 
carefully  handled  to  avoid  crushing.  Study  in  a  watch  glass 
of  sea  water  (or  support  the  cover  glass)  with  a  low  power 
of  the  microscope. 

1.  Notice  that  the  individuals  are  very  much  like  minia- 
ture Molgulas.  Identify  as  many  of  the  organs  that  were 
seen  in  Molgula  as  possible,  noting  the  differences. 

2.  The  form  illustrates  the  type  (Clavelinidae)  in  which 
a  colony  is  formed  by  budding  from  a  stolon,  but  in  which 
the  individuals  retain  their  identity  to  a  great  degree  and 
have  separate  tunics. 

3.  Study  the  stolon  with  its  flattened  epicardiac  tube. 
This  tube  is  derived  from  the  branchial  sac  and  is  accord- 
ingly endodermic. 


PEROPHORA,  BOTRYLLUS  239 

4.  Study  buds  of  various  sizes  and  see  how  the  inner  ves- 
icles arise  from  the  epicardiac  tube. 

5.  Try  to  make  out  the  entire  course  of  the  circulation  of 
the  blood.  Notice  especially  the  heart,  branchial  vessels, 
vessels  of  the  mantle,  and  the  circulation  of  the  stolon. 
Watch  the  pulsations  of  the  heart  and  see  the  reversal  of  the 
blood  current.  Is  the  heart  beat  synchronous  in  different 
individuals?    What  part  of  the  blood  is  colored? 

6.  Study  the  action  of  the  cilia  in  the  gill  clefts. 
Drawings  of  a  colony  and  of  an  individual  are  desirable. 

Lefevre:    Budding  in  Perophora.    Jour.  Morph.,  14,  1898. 

BOTRYLLUS 

The  small,  radially  arranged  colonies  of  this  composite 
ascidian  are  common  on  eel  grass,  from  which  they  may  be 
separated  by  means  of  a  knife,  and  studied  alive  in  a  watch 
glass  with  a  lower  power  of  the  microscope.  The  cleaner  and 
more  transparent  colonies  should  be  selected. 

1.  Note  the  character  which  makes  the  form  a  "compo- 
site" ascidian — the  common  tunic  or  test.  Find  the  mouths 
and  the  common  cloacal  cavity.  Would  it  be  correct  to  say 
that  a  common  atrium  is  present? 

2.  Find  the  annular  blood  vessel  and  its  numerous  am- 
pullae. Do  you  observe  any  striking  facts  regarding  the  cir- 
culation?   What  functions  have  the  ampullae? 

3.  With  your  knowledge  of  Molgula  as  a  guide,  identify 
as  many  of  the  organs  as  possible.  (This  is  sometimes  diffi- 
cult because  of  pigment.) 

4.  Very  young  colonies,  with  only  the  first  one  or  two 
generations  of  buds,  may  also  be  found  on  eel  grass,  appear- 
ing as  transparent  hemispherical  lumps  about  a  millimeter  in 
diameter.  These  should  be  fixed  and  stained  on  the  eel  grass, 
and  later  mounted  (either  still  attached  or  removed)  in  bal- 
sam. These  will  show  very  clearly  the  formation  of  buds  of 
the  "parietal"  or  "peribranchial"  type.  (In  this  type  the 
outer  vesicle  arises  from  the  integument,  and  the  inner  vesicle 


240  CHORDATA 

from  the  parietal  wall  of  the  atrial  cavity.)  The  inner  vesicle 
may  be  seen  partly  constricted  into  three  divisions — the 
pharynx  and  the  two  atrial  sacs.  From  which  "germ  layer" 
then  are  these  parts  in  the  bud  derived? 

5.  Look  for  the  tailed  larvae  or  "tadpoles"  near  the  sur- 
face and  on  the  side  turned  toward  the  light,  in  a  dish  in 
which  Botryllus  has  been  kept  for  an  hour  or  two.  Is  this 
positive  phototropism  advantageous?  Examine  a  larva  under 
a  microscope. 

Drawings  of  the  adult,  the  young  colony,  and  the  larva 

are  desirable. 

Grave  and  Woodbridge:   Botryllus  schlosseri,  Pallas:   The  Behavior  and 
Morphology  of  the  Free-swimming  Larva.    Jour.  Morph.,  39,  p.  207, 

1924. 
Herdman,  E.  C:    Botryllus.     Liverpool  Marine  Biol.  Com.  Memoirs, 

xxvi,  1924. 

AMAROUCIUM    (Sea  Pork) 

Different  species  of  this  composite  ascidian  live  at  differ- 
ent depths  and  show  minor  structural  differences,  especially 
in  the  tests.  Colonies  may  be  found  abundantly  on  piles  and 
they  are  frequently  brought  up  with  a  dredge. 

1.  Compare  the  grouping  of  the  individual  in  the  colony 
with  Botryllus.  Is  there  any  regularity  in  the  number  of  a 
group  connected  with  a  common  cloacal  cavity? 

2  With  a  sharp  knife,  cut  a  section  vertical  to  the  surface 
of  the  mass,  and  2  or  3  mm.  thick,  and  study  it  with  a  low 
power  of  the  microscope.  Other  pieces  should  be  squeezed 
in  a  fingerbowl  half  full  of  sea  water,  the  expressed  material 
(adult  animals,  fragments,  embryos,  etc.)  allowed  to  settle, 
and  then  rinsed  with  clean  sea  water.  A  few  entire  adults 
may  be  picked  out  with  a  pipette. 

In  the  adult  animal  you  may  find: 

(a)  Oral  and  atrial  openings. 

(b)  Pharynx,  with  the  peripharyngeal  bands  and  en- 
dostyle,  esophagus,  the  orange-brown  corrugated  stomach, 
and  intestine. 


BOTRYLLUS,    AMAROUCIUM  241 

(c)  The  cerebral  ganglia. 

(d)  The  long  postabdomen,  with  its  hollow  epicardium 
connected  with  the  pharynx.  (The  postabdomen  is  really  a 
stolon.  Recall  Perophora.)  If  complete,  the  red-pigmented 
tip  will  be  seen. 

(e)  The  slowly  pulsating  U-shaped  heart,  situated  very 
near  the  tip  of  the  postabdomen. 

3.  In  the  atrium,  which  serves  as  a  brood  pouch,  embryos 
in  all  stages  may  be  found.  How  do  the  eggs  compare  in  size 
with  those  of  Molgula? 

4.  Look  for  buds  formed  by  segmentation  of  the  post- 
abdomen (stolon) .  The  "inner  vesicle"  of  these  buds,  which 
gives  rise  to  the  alimentary  canal  and  atrial  sacs,  comes  from 
the  endodermic  epicardium,  as  in  Perophora.  Compare  this 
with  Botryllus. 

5.  If  the  material  squeezed  in  the  fingerbowl  was  quite 
fresh,  living  embryos  in  all  stages  of  development  can  be 
found.  Fresh  specimens  kept  in  a  large  jar  of  sea  water  dur- 
ing the  summer  will  discharge  larvae.  These  swim  rapidly, 
and  usually  swim  away  from  the  light.  Does  this  correspond 
with  Botryllus?    Is  this  negative  phototropism  adaptive? 

The  tailed  larvae  may  be  picked  up  with  a  pipette  while 
swimming,  dropped  into  fixing  fluid,  and  finally  stained  and 
mounted.  Others  may  be  transferred  to  watch  glasses  and 
studied.  If  the  larvae  are  kept  in  watch  glasses  of  sea  water 
for  some  hours  some  will  attach.  The  dishes  may  be  kept 
in  a  cage  under  a  wharf  submerged  in  sea  water,  or  in  a  dish 
where  pure  sea  water  can  be  conducted  to  it.  Under  these 
conditions  they  will  develop  readily,  but  they  must  be  kept 
clean  from  sediment  by  washing  them  with  a  gentle  current 
at  least  twice  a  day. 

In  larvae  that  have  been  previously  stained  and  mounted 
observe : 

(a)  The  shape  of  the  animal  and  its  division  into  body 
and  tail. 

(b)  The  thick  test,  and  the  oral  and  atrial  openings. 
16 


242  CHORDATA 

(c)  The  adhesive  organs.    How  many  are  there? 

(d)  The  notochord.    How  far  does  it  extend? 

(e)  The  tail  muscles. 

(/)   The   pharynx,   with   as   yet   few   gill   clefts,   the   en- 
dostyle,  esophagus,  stomach,  intestine,  and  yolk  mass, 
(g)  The  cerebral  vesicle  with  the  eye  spot  and  otolith. 

If  young  individuals  that  have  been  attached  but  a  short 
time,  but  have  lost  their  tails,  are  stained  and  mounted,  they 
will  be  found  very  instructive  when  compared  with  the  larva. 
The  complete  degeneration  of  the  tail  and  the  final  rotation 
into  the  position  of  the  adult  can  be  traced  in  a  series  of  in- 
dividuals. 

Drawings  of  an  adult  individual,  of  a  larva,  and  of  a 
young  individual  are  desirable. 

van  Name:    Compound  Ascidians  of  the  Coasts  of  New  England  and 
Neighboring  Provinces.    Proc.  Bost.  Soc.  Nat.  Hist.,  34,  1910. 

SALPA  CORDIFORMIS 

Examine  a  specimen  in  a  bowl  of  water  without  dissect- 
ing.   Use  a  hand  lens. 

Sexual  form  (occurring  in  chains) : 

1.  Note  the  transverse  muscle  bands.  How  many  bands 
are  there?  Are  they  complete  or  interrupted?  Do  you  know 
what  they  are  for? 

2.  The  oral  aperture  is  dorsal  and  far  forward.  Are  there 
any  muscles  for  opening  and  closing  it? 

3.  What  is  the  form  and  position  of  the  cloacal  aperture? 
Is  it  provided  with  muscles? 

4.  Observe  the  processes  of  the  tunic,  one  anterior,  one 
midventral  and  two  posterior.  These  processes  (except  the 
dorsal  posterior)  serve  to  unite  the  individuals  of  the  chain. 

5.  Does  the  animal  show  perfect  bilateral  symmetry? 

6.  Posterior  to  the  mouth,  the  ganglion  and  the  pigmented 
eye  spot  may  be  found.  Immediately  anterior  to  these  is 
the  elongate  hypophysis. 


SALPA,    AMPHIOXUS  243 

7.  Note  the  endostyle  in  the  floor  of  the  pharynx,  and  the 
dorsal  lamina  between  the  pharynx  and  atrial  cavity.  From 
the  anterior  end  of  the  dorsal  lamina  the  peripharyngeal 
bands  extend  to  the  anterior  end  of  the  endostyle. 

8.  The  pharynx  communicates  laterally  with  the  atrium 
by  means  of  two  very  large  stigmata.  These  are  probably 
homologous  with  the  numerous  stigmata  of  Molgula. 

9.  The  "nucleus"  the  large  mass  in  the  posterior  end  of 
the  body,  contains  the  stomach  and  intestine. 

The  ova  are  fertilized  by  spermatozoa  from  individuals 
of  another  chain,  since  in  the  same  chain  the  spermatozoa 
mature  much  later  than  the  ova.  The  fertilized  ova  migrate 
to  a  spot  in  the  right  wall  of  the  atrium,  where  they  develop 
into  the  solitary,  nonsexual  Salpa. 

In  this  species  as  many  as  three  or  four  embryos  may  be 
seen  attached  by  "placentae"  to  the  cloacal  wall  on  the  right 
side.  The  placental  connection  finally  separates,  and  the 
embryo  passes  out  through  the  cloacal  aperture. 

Make  an  enlarged  drawing  (a  laterodorsal  view  is  best). 

Brooks:    The  Genus  Salpa.    Mem.  Biol.  Lab.  Johns  Hopkins  Univ.,  2, 

1893. 
Grobben:     Doliolum    und    sein    Generationswechsel.     Arb.  Zool.    Inst. 

Wien,  4,  1882. 
Metcalf:    The  Salpidse:    A  Taxonomic  Study.    Bull.  U.  S.  Nat.  Mus., 

100,  1918. 

CEPHALOCHORDA 

AMPHIOXUS  LANCEOLATUS 

While  living  material  is  not  easily  provided  for  labora- 
tory work,  it  should  be  understood  that  this  form  spends 
most  of  its  time  in  the  sand  in  rather  shallow  water  and  that 
it  burrows  with  great  ease  by  movements  of  the  body. 

1.  In  an  alcoholic  specimen  note  the  dorsal,  ventral,  and 
caudal  regions,  and  also  the  median  fin,  metapleural  folds, 
muscle  plates  or  myotomes,  buccal  cavity  fringed  with  cirri, 
atriopore,  and  anus. 

2.  Using  a  specimen  that  has  been  macerated  in  20  per 
cent  nitric  acid,  remove  the  skin  and  myotomes  from  the 


244  CHORDATA 

right  side  very  carefully,  by  means  of  needles,  exposing  the 
notochord,  nerve  cord,  gonads,  and  the  entire  alimentary 
canal  (pharynx,  intestine,  and  digestive  diverticulum  or 
"liver,"  which  lies  along  the  right  side  of  the  pharynx) . 

3.  Examine  microscopically  and  notice: 

(a)  The  nerve  cord,  cerebral  vesicle,  cerebral  nerves,  eye 
spot,  and  pigment  cells.  Note  also  the  alternate  metamerism 
of  the  spinal  nerves. 

(6)  The  buccal  skeleton. 

(c)  A  large  piece  of  the  pharyngeal  wall. 

4.  Examine  an  Amphioxus  1  cm.  in  length,  stained  and 

mounted. 

Identify  as  many  as  possible  of  the  structures  mentioned 
above,  and  in  addition  note:  the  olfactory  pit,  oral  velum 
with  velar  tentacles,  and  ataste  organ"  in  the  buccal  cavity. 

A  drawing  showing  the  general  structure  is  desirable. 
5.  Make  thick  free-hand  sections  of  various  regions  and 
study  with  a  low  power  in  a  watch  glass,  to  supplement  the 
study  of  stained  sections. 

6.  Prepared  sections  should  be  studied  that  show  the  fol- 
lowing five  regions:  (a)  buccal  cavity;  (b)  anterior  part 
of  pharynx;  (c)  posterior  part  of  pharynx  with  gonads  and 
liver;   (d)  atriopore;   (e)   anus. 

The  five  sections  should  be  studied  with  a  low  power  and 
drawn.  In  (b)  (anterior  part  of  pharynx),  note  especially 
the  limits  of  the  coelom  and  atrium,  the  lymph  spaces  in  the 
metapleural  folds,  the  two  dorsal  aortae,  the  ventral  aorta, 
the  epibranchial  groove,  the  endostyle,  the  subendostylar 
coelom,  and  the  two  kinds  of  gill  bars,  primary  and  tongue 

bars. 

With  a  high  power  study  the  nerve  cord  (best  shown  in 
region  a)  and  the  gill  bars  and  endostyle  (best  shown  in  re- 
gion b). 

Drawings  of  these  regions  are  desirable. 

Willey:    Amphioxus  and  the  Ancestry  of  Vertebrates.    Columbia  Univ. 
Press. 


NOTES  FOR  GUIDANCE  IN  MAKING  PERMANENT 

PREPARATIONS 

Only  very  simple  directions  are  here  given,  such  as  will 
serve  to  aid  students  who  have  had  no  experience  in  prepar- 
ing objects  for  microscopic  examination  to  make  preparations 
when  this  is  desirable  for  proper  laboratory  study.  The  best 
simple  directions  for  technique  of  this  type  may  be  found  in 
Guyer's  Animal  Micrology.  Another  excellent  guide  is 
Galigher's  Practical  Microtechnique. 

For  more  elaborate  work  McClung's  Microscopical 
Technique  or  Lee's  Microtomist's  Vade  Mecum  are  valuable. 

The  steps  taken  in  preparing  total  mounts  include: 

1.  Narcotizing  or  anesthetizing. 

2.  Fixing  or  killing. 

3.  Washing. 

4.  Dehydrating  and  staining. 

5.  Clearing. 

6.  Mounting. 

Narcotizing. — A  great  many  animals  or  animal  parts  may 
be  more  easily  fixed  if  first  anesthetized.  Many  invertebrates 
can  be  anesthetized  by  placing  in  a  dish  with  an  ample  sup- 
ply of  water  to  which  crystals  of  magnesium  sulphate  are 
then  added.  As  the  crystals  dissolve  add  more  until  anes- 
thetization is  complete.  This  method  is  especially  good  for 
delicate  hydroids.  Other  narcotizing  agents  which  may  be 
used  include  the  following:  (l)  chloretone,  which  may  be 
used  similarly  to  the  method  given  for  magnesium  sulphate. 
Many  small  invertebrates  may  be  transferred  directly  to 
dilute  solutions  of  chloretone,  e.  g.,  annelids  (one  part  satu- 
rated aqueous  solution  of  chloretone  to  four  to  nine  parts  of 
water) .  For  marine  animals  this  solution  should  be  made  up 
in  sea  water. 

245 


246        GUIDANCE   IN   MAKING   PERMANENT   PREPARATIONS 

(2)  Ethyl  alcohol.  Animals  may  be  transferred  gradually 
or  directly  to  concentrations  of  alcohol  varying  from  1  to  8 
per  cent. 

For  finer  cytological  work  it  is  well  to  avoid  any  use  of 
anesthetics. 

Fixing. — This  is  necessary  in  order  to  keep  the  cells  and 
tissues  as  nearly  as  possible  in  their  natural  position,  shape, 
and  structure,  and  in  order  that  the  protoplasm  composing 
them  may  be  kept  in  condition  to  stain  satisfactorily. 

In  selecting  a  fixing  agent  remember: 

1.  If  the  material  is  highly  irritable  and  contractile,  it 
will  have  to  be  killed  practically  instantly  with  hot  solutions, 
or  be  previously  narcotized. 

2.  If  there  is  much  lime,  an  agent  that  contains  much 
acid  should  not  be  used,  as  the  lime  will  be  dissolved  and 
the  bubbles  of  gas  are  likely  to  tear  or  distort  tissues. 

3.  Where  rapid  fixation  is  desirable,  as  in  expanded  hy- 
droids  and  the  like,  hot  Bouin's  picroformol  or  hot  sublimate- 
acetic  is  preferable.  Where  the  tissue,  or  the  animal,  is  not 
especially  muscular,  or  liable  to  contraction,  any  of  the  fluids 
may  be  used.  The  time  that  objects  should  be  left  in  the 
killing  solution  varies,  approximately,  directly  as  their  size. 
Three  minutes  will  suffice  for  killing  hydroids  in  Bouin's 
picroformol  or  sublimate-acetic. 

Washing. — All  objects  must  be  thoroughly  washed,  after 
using  most  killing  agents.  With  most  small  objects  alcohol 
is  preferable,  but  if  the  object  is  large  this  is  too  expensive. 
In  general  the  material  used  for  washing  will  depend  on  the 
fixative  employed.    See  Guyer. 

Dehydrating  and  Staining. — From  water,  all  objects 
should  be  placed  successively  in  35  per  cent,  50  per  cent,  and 
70  per  cent  alcohol,  five  to  fifteen  minutes  in  each  for  small 
objects,  such  as  protozoa  or  individual  hydroids.  In  subse- 
quent changes  from  one  grade  to  another  allow  about  the 
same  time.  All  tissues  killed  in  a  corrosive  sublimate  mix- 
ture should  now  be  treated  with  a  weak  solution  of  iodine, 


DEHYDRATING   AND   STAINING 


247 


to  dissolve  the  corrosive  sublimate  that  still  remains,  and 
thus  prevent  the  later  formation  of  crystals  of  that  substance. 
Such  crystals  would  not  appear  immediately,  but  ever  in- 
creasingly, as  the  preparation  is  kept.  Put  a  few  drops  of 
iodine  into  the  70  per  cent  alcohol  containing  the  object, 
leave  a  few  minutes,  and,  if  the  yellow  color  caused  by  the 
iodine  has  disappeared,  pour  off  the  alcohol  and  use  more 
70  per  cent  alcohol  with  iodine,  as  before.  The  bleaching  in- 
dicates that  some  corrosive  sublimate  remains.  Repeat  until 
the  yellow  color  does  not  fade.  Then  transfer  to  clear  70 
per  cent  alcohol.  At  this  point  either  staining,  or  prepara- 
tion for  so  doing,  begins. 

In  case  the  stain  you  wish  to  use  is  a  70  per  cent  alcoholic 
solution,  it  may  be  used  immediately.  Otherwise,  the  object 
must  be  run  through  the  grades  of  alcohol,  up  or  down  as  the 
case  may  be,  to  that  medium  in  which  the  stain  to  be  used  is 
dissolved.  If  an  aqueous  stain  such  as  alum  carmine  is  to 
be  used,  pass  through  50  per  cent  and  35  per  cent  alcohol  to 
water.  If  a  95  per  cent  alcoholic  stain  is  to  be  used,  pass 
through  80  per  cent  and  95  per  cent  alcohol. 

The  time  an  object  should  be  treated  with  stain  varies 
with  the  stain  and  the  size  of  the  object.  Alum  carmine 
should  be  used  from  six  to  twenty  hours,  according  to  cir- 
cumstances. Borax  carmine  should  be  used  for  from  five 
minutes  to  half  an  hour.  Aceto-carmine,  used  for  killing  and 
staining,  acts  very  rapidly.  Delafield's  hematoxylin  (a  dark 
wine-colored  solution  in  water)  requires  ten  minutes  to  half 
an  hour.  In  all  these  cases,  examination  of  the  objects  them- 
selves is  the  only  means  of  deciding  when  staining  is  suffi- 
cient. It  is  usually  best  to  overstain  slightly  and  then  to 
bleach  out,  as  certain  parts  of  the  protoplasmic  structure 
will  retain  the  stain  better  than  others,  and  thus  better  dif- 
ferentiation will  be  secured.  After  staining,  bring  the  tissues 
gradually  into  70  per  cent  alcohol,  and  then  treat  with  acidu- 
lated alcohol  to  remove  excess  of  stain.  After  this,  every 
trace  of  the  acid  must  be  removed  by  washing  in  clean  al- 


248        GUIDANCE   IN    MAKING   PERMANENT   PREPARATIONS 

cohol,  or  the  tissues  will  continue  to  bleach  after  they  are 
mounted.  The  specimen  is  now  ready  for  final  dehydration. 
In  damp  climates,  as  at  the  seashore,  your  stronger  alcohols 
must  be  kept  closely  covered  all  of  the  time  or  they  will  take 
water  from  the  atmosphere  and  be  unfit  for  the  purpose. 
Absolute  alcohol  may  be  kept  from  excessive  dilution  under 
these  conditions  by  placing  in  it  a  fine-mesh  cloth  bag  con- 
taining anhydrous  copper  sulphate  which  must  be  renewed 
from  time  to  time.  Run  through  80  per  cent,  95  per  cent, 
and  100  per  cent  alcohol,  thus  completing  dehydration. 
Every  trace  of  water  must  be  removed  and  then  kept  out. 

Clearing  and  Mounting.1 — From  absolute  alcohol,  place 
objects  in  some  clearing  fluid  (clove  oil,  cedar  oil,  or  xylol) 
and  leave  till  they  have  a  clear,  translucent  appearance,  after 
which  place  on  a  clean  slide,  with  some  Canada  balsam  or 
damar,  and  cover  with  a  cover  glass. 

If  the  object  turns  cloudy  or  milky  when  placed  in  the 
cleaning  fluid,  it  is  evidence  that  all  of  the  water  has  not  been 
removed,  and  it  should  be  returned  to  absolute  alcohol  for 
complete  dehydration.  Tissues  left  in  the  clove  oil  or  xylol 
for  any  great  length  of  time  will  become  hard  and  brittle. 
In  case  tissues  in  the  process  of  preparation  must  neces- 
sarily be  left  untreated  for  several  days,  they  should  be  left 
in  a  70  per  cent  or  80  per  cent  alcoholic  medium. 

Sectioned  Material. — In  a  few  cases  sectioned  material, 

previously  stained  in  toto,  may  be  distributed  to  the  class.  Be 

sure  that  the  slide  on  which  you  intend  mounting  the  sections 

is  thoroughly  clean.    Remove  any  greasy  substance  with  95 

per  cent  alcohol.     On  a  cleaned  slide,  smear  a  very  little 

albumen  fixative  with  your  fingertip  and  remove  all  except 

the  thinnest  film.    On  water  placed  over  this  film  of  albumen 

float  the  sections.    Very  gently  heat  the  water  until  the  sec- 

1  Specimens  may  be  successfully  mounted  in  euparal  from  95  per 
cent  alcohol.  This  avoids  labor  of  dehydration  and  clearing  and  gives 
permanent  mounts.  For  total  mounts  of  parapodia,  etc.,  methyl  salic- 
ylate (synthetic  oil  of  wintergreen)  may  be  used  to  clear  directly 
from  95  per  cent  alcohol. 


APPLICATION   OF   ABOVE   DIRECTIONS   IN    CASE   OF  HYDROID     249 

tions  stretch  out  flat,  but  do  not  melt  the  paraffin.  Carefully 
drain  off  excess  water  and  set  slides  aside  to  dry.  If  the  air 
is  dry,  the  slides  should  be  ready  for  further  treatment  in 
about  twelve  hours.  The  value  of  this  method  is  that  it  gives 
perfectly  flat  sections.  At  the  end  of  this  time  the  slides 
may  be  placed  in  xylol  to  dissolve  the  paraffin.  When  the 
paraffin  is  completely  dissolved  (this  will  take  a  few  minutes) , 
drain  off  the  xylol,  apply  a  drop  of  balsam,  and  cover  as  in 
total  mounts.  The  preparation  is  now  ready  for  use,  and  is 
permanent,  but  must  be  handled  carefully  while  fresh. 

Application  of  Above  Directions  in  the  Case  of  a  Hydroid : 
Hot  Bouin's  picroformol,  fifteen  seconds. 
Cold  Bouin's  picroformol,  five  to  fifteen  minutes. 
Fifty  per  cent  alcohol,  four  changes,  three  or  four  min- 
utes each. 
Seventy  per  cent  alcohol,  five  minutes. 
One  half  of  your  material  may  now  be  placed  in  borax  car- 
mine.   Leave  the  material  in  this  till  objects  have  taken  on 
a  good  color.     (Ask  an  instructor  about  this.)     When  suffi- 
ciently stained,  put  into  acidulated  alcohol  till  the  color  as- 
sumes a  brilliant  appearance,  but  do  not  allow  it  to  fade  too 
far.    Wash  in  70  per  cent  and  then  run  through  80  per  cent 
and  95  per  cent  alcohol,  five  minutes  each,  and  mount  directly 
in  euparal. 

If  balsam  is  to  be  used,  continue  from  the  95  per  cent 
alcohol  to  100  per  cent  alcohol,  five  minutes,  thence  into 
clove  oil,  or  cedar  oil,  keeping  all  reagents  carefully  covered, 
and  leave  till  the  object  is  thoroughly  penetrated.  This  lat- 
ter process  may  take  five  to  ten  minutes. 

If,  on  putting  your  objects  into  the  clearing  medium,  the 
latter  exhibits  a  milky-white  appearance,  the  material  is  not 
sufficiently  dehydrated,  and  must  be  returned  to  100  per  cent 
alcohol. 

After  clearing  is  completed,  put  the  object  on  a  clean 
slide  with  a  little  balsam  and  cover. 

The  material  not  treated  with  borax  carmine  may  be  run 


250        GUIDANCE   IN   MAKING   PERMANENT   PREPARATIONS 

back  through  50  per  cent  and  35  per  cent  alcohol  to  water, 
to  which  a  few  drops  of  hematoxylin  has  been  added,  or  put 
from  water  into  alum  carmine.  The  former  stain,  if  dense, 
should  not  require  over  twenty  to  thirty  minutes,  but  objects 
must  be  left  in  alum  carmine  ten  to  twenty  hours.  When  a 
good  color  is  obtained,  run  the  material  through  the  grades 
of  alcohol,  from  the  lowest  to  the  highest  (five  minutes  in 
each),  and  mount  as  in  the  case  of  the  borax  carmine  objects. 
Objects  stained  in  alum  carmine  will  probably  not  over- 
stain;  but  excess  of  hematoxylin  should  be  extracted  with 
acidulated  alcohol  when  the  70  per  cent  grade  is  reached, 
after  which  it  is  very  essential  that  all  of  the  acid  be  re- 
moved by  repeated  changes  of  70  per  cent  alcohol.  Other- 
wise the  objects  will  fade. 


GLOSSARY 


Note:  The  definitions  given  below  are,  of  course,  intended  pri- 
marily to  apply  to  the  invertebrates.  With  a  few  exceptions  no  attempt 
has  been  made  to  supply  the  meanings  which  apply  to  the  vertebrates. 

Abdomen.     In  invertebrates,  the  posterior  division  of  the  body. 
Aboral  surface.     The  surface  of  the  body  opposite  the  oral  or  mouth 

surface. 
Aciculum.     A  supporting  rod  in  an  annelid  parapodium. 
Acinous.     Saccular  or  granular. 

Acontium.  In  sea  anemones,  a  threadlike  organ  containing  nettle  cells. 
Acraspedote  medusa.  A  medusa  without  velum.  Typical  of  Scyphozoa. 
Acrocyst.     An  extracapsular  brood  chamber  attached  to  distal  end  of 

gonosome  in  certain  calyptoblastic  hydroids. 
Actinopharynx.      Tube    leading    from    mouth    to    coelenteron    in   sea 

anemones. 
Actinule  or  actinula.    A  specialized  larval  form,  having  aboral  and  oral 

tentacles   and    developed   in   the    medusa    of   tubularian   hydroids. 

Ultimately  gives  rise  to  a  new  colony. 
Adductor   muscle.     A    closing    or   withdrawing    muscle. 
Adhesive  organ.    A  sucker  or  sticky  pad  that  will  adhere. 
Adnate.    Said  of  hydranths  growing  with  one  side  adherent  to  a  stem. 
Adradial  canal.    In  a  medusa,  a  canal  lying  between  adjacent  per-  and 

inter-radial  canals. 
Afferent.    Carrying  toward,  as  a  vessel  which  leads  to  an  organ. 
Alga.     A  simple  cholorphyl-bearing  plant. 
Alimentary  canal.    Digestive  tube. 

Alternation  of  generations.     Alternation  of  sexual  and  asexual  genera- 
tions in  the  life  cycle  of  an  organism. 
Alveolus.    A  little  sac  or  cavity;  also  one  of  the  plates  that  bears  the 

teeth  in  an  echinoid. 
Ambulacral  area.     The  region  bearing  the  tube  feet  of  an  echinoderm. 
Ambulacral  foot.    A  tube  foot  of  an  echinoderm. 
Ambulacral  groove.     One  of  the  depressions  in  which  the  tube  feet  of 

a  starfish  are  placed. 
Ambulacral  plate.     One  of  the  plates  of  an  ambulacral  area. 

251 


252  GLOSSARY 

Ambulacral  pore.    The  opening  through  which  a  tube  foot  projects. 

Ambulacral  ridge.  The  elevation  in  the  coleom  of  starfish  arm,  caused 
by  the  ambulacral  plates. 

Ambulacral  sucker.     The  sucker  at  the  end  of  a  tube  foot. 

Amphiblastula.     A  characteristic  embryonic  stage  of  a  sponge. 

Ampulla.    A  reservoir  connected  with  the  tube  foot  of  an  echinoderm. 

Anal  plate.  In  the  periproct  of  an  echinoid,  the  plate  in  which  the 
anus  lies. 

Analogous.     Similar  in  function. 

Anastomosis.  In  the  simplest  form,  a  cross  connection  between  two 
adjacent  blood  vessels  or  nerves.  Frequently  many  such  cross  con- 
nections among  several  related  vessels  or  nerves  result  in  the  forma- 
tion of  a  network, 

Annulation.  A  ringlike  part  or  annulus  as  in  the  ringed  stem  of  cer- 
tain hydroids. 

Annulus.    A  ring  or  ringlike  part  or  structure. 

Antenna.    A  sensory  head  appendage  of  an  arthropod. 

Antennule.  A  sensory  paired  head  appendage  of  an  arthropod,  placed 
just  anterior  to  the  antenna  when  present.  Usually  designated  as 
first  antenna. 

Anterior.    Front  or  head  end. 

Anteroposterior.    Lengthwise  of  the  body. 

Anus.  The  opening  (usually  posterior)  of  the  alimentary  canal  through 
which  the  feces  are  discharged. 

Apical  plate.  An  ectodermal  thickening  at  the  anterior  end  of  trocho- 
phore  larva. 

Apical  system.  A  group  of  plates  surrounding  the  periproct  of  an 
echinoid. 

Apical  tuft.    A  group  of  large  cilia  on  the  apical  plate. 

Apopyle.  The  opening  of  a  radial  canal  of  a  sponge  into  the  gastric 
cavity  or  cloaca. 

Arthrobranch.  A  gill  of  a  crustacean,  borne  by  the  articular  membrane 
at  the  base  of  an  appendage.     A  joint  gill. 

Asexual  reproduction.  Keproduction  without  sexual  phenomena,  e.  g., 
binary  fission,  multiple  fission   (sporulation),  budding,  etc. 

Atriopore.    External  opening  of  the  atrium. 

Atrium.     In  tunicates  and  Amphioxus,  a  chamber  partly  enclosing  the 
pharynx  and  receiving'  water  from  the  latter  through  the  pharyngeal 
slits.    Genital  products  and,  in  adult  tunicates,  feces  also  pass  into 
the  atrium. 
Auricle.    A  receiving  chamber  of  the  heart. 

Avicularium.  A  structure  shaped  like  a  bird's  head,  present  in  some 
Bryozoa. 


GLOSSARY 


253 


Axial  organ.  A  structure  near  the  stone  canal  of  echinoderms  which  is 
apparently  connected  with  genital  organs. 

Basipod.  Second  segment  from  proximal  end  of  protopod  in  a  crus- 
tacean appendage. 

Beak.  Horny  mouth  parts;  the  point  from  which  growth  has  proceeded 
in  a  clam  shell.     Cf.  Umbo. 

Bilateral  symmetry.  Body  plan  such  that  the  organism  may  be  cut 
in  but  one  plane  to  produce  equivalent  or  mirror-image  halves 
(right  and  left). 

Biramous.  Composed  of  two  branches,  as  a  typical  crustacean  appen- 
dage. 

Bivalve.    Having  two  valves  or  pieces,  as  a  clam  shell. 

Bivium.  The  two  rays  of  a  starfish  which  are  nearest  the  madreporic 
plate. 

Blastostyle.  The  reproductive  zooid  (probably  a  degenerate  hydranth) 
in  certain  hydroids.  The  gonophores  (sporosacs  and  medusae)  are 
developed  on  the  blastostyle. 

Body  cavity.    See  Coelom. 

Body  wall.    The  outer  wall  of  the  body. 

Brain.    In  invertebrates,  frequently  applied  to  the  cerebral  ganglia. 

Branchiae.    Gills;  organs  adapted  for  aquatic  respiration. 

Branchial  heart.  An  accessory  heart  placed  at  the  base  of  a  gill,  as  in 
the  squid. 

Brood  sac.    A  cavity  or  pouch  in  which  developing  embryos  are  carried. 

Bud.     An  outgrowth  or  ingrowth  which  will  become  a  new  individual. 

Byssal  gland.  A  gland  in  the  reduced  foot  of  certain  pelecypods,  e.  g., 
Mytilus.  It  produces  the  byssal  threads,  collectively  known  as  the 
byssus. 

Byssal  thread.     One  of  the  threads  by  which  certain  pelecypods  attach 

themselves. 

Caecum.    A  blind  saclike  outgrowth  of  the  alimentary  canal. 

Calciferous  glands.    Esophageal  glands  of  some  annelids. 

Calyptoblastic.     Possessing  hydrothecae  and  gonothecae. 

Capitate  tentacle.     One  which  is  enlarged  or  globose  at  its  distal  end. 

Carapace.     The  covering  of  the  head  and  thorax  in  some  crustaceans. 

Cardiac  stomach.    Anterior  or  first  division  of  the  stomach. 

Caudal  cirrus.    A  cirrus  found  on  the  caudal  end,  especially  of  nemer- 

tines  and  annelids. 
Carpopod.    Third  segment  from  proximal  end  of  endopod  in  Crustacea. 
Cellulose.     The  most  important  material  in  the  walls  of  plant  cells.    A 

cellulose-like   substance    (tunicin)    is  found  in  the   tunic  of  many 

Urochorda. 


254  GLOSSARY 

Cephalont.    Attached  stage  in  the  life  history  of  Gregarina. 
Cephalothorax.     Fused  head  and  thorax  in  many  crustaceans. 
Cervical  groove.    A  groove,  in  the  carapace,  which  marks  the  boundary 

between  the  head  and  the  thorax. 
Chela.    Large  claw  of  many  crustaceans ;  also  applied  to  pincer-like  claws 

on  other  appendages. 
Chelate.    Bearing  pincer-like  claws. 

Chelicera.    One  of  the  anterior  pair  of  mouth  appendages  of  Arachnida. 
Chitin.     The  material  which  forms  the  outer  covering  of  insects  and 

many  other  invertebrates. 
Chlorogogue.    Modified  cells  of  the  peritoneal  covering  of  the  intestine 

in  annelids. 
Chlorophyl.     The  green  coloring  matter  of  plants. 
Chloroplastid.     One  of  the  chlorophyl-containing  bodies  within  certain 

cells  of  green  plants. 
Choanocyte.     A  "collar  cell."     e.  g.,  Choanoflagellates  and  the  gastric 

layer  in  sponges. 
Chromatophore.     In  zoology,  a  pigment-bearing  tissue  element  or  cell; 

in  botany,  a  colored  body  or  plastid  found  commonly  in  plant  cells, 

e.  g.,  a  chloroplastid. 
Cilia   (sing.,  Cilium).     Minute,  hairlike,  motile,  protoplasmic  processes 

of  cells,   e.  g.,  ciliate   protozoa.     Also   widespread  throughout  the 

animal  kingdom. 
Cinclides    (sing.,   Cinclis).     Minute   openings  in   the   body  wall   of  sea 

anemones. 
Circular  canal.    Marginal  canal  of  a  medusa;  also  applied  to  the  water 

canal  which  surrounds  the  mouth  of  an  echinoderm. 
Circumferential  canal.     Circular  canal  of  a  medusa. 
Cirrus.     A   soft,   elongate   outgrowth   or   appendage;    in   protozoa,  an 

organelle  composed  of  a  cluster  of  fused  cilia. 
Cleavage.    Eapid  cell  division  not  accompanied  by  growth. 
Clitellum.     The  thickened,  glandular  region  which  secretes  the  cocoon 

of  an  earthworm. 
Cloaca.     The  modified  posterior  part  of  the  alimentary  canal  which 

receives  products  from  the  excretory  organs  and  frequently  from 

other  organs. 
Cnidoblast.     Stinging  cell  in  coelenterates.     Contains  the  nematocyst. 
CnidociL     Slender  process  of  a  cnidoblast,  stimulation  of  which  may 

cause  the  ejection  of  the  nematocyst. 
Coelenteron.    The  digestive  cavity  of  a  coelenterate. 
Coelom  or  true  body  cavity.    The  cavity  between  the  alimentary  canal 

and  the  body  wall.    Lined  with  mesoderm. 
Coenosarc.     The  living  part  of  the  stalk  of  a  coelenterate.     It  is  con- 
tinuous with  the  polyps. 


GLOSSARY  255 

Collar  cell.     A  cell  provided  with  a  protoplasmic  collar;   choanocyte. 

Colon.    Variously  applied  to  a  portion  of  last  part  of  digestive  tract. 

Columella.    Axis  around  which  the  spire  of  a  gastropod  shell  is  wound. 

Commensal.  Organisms  living  together  and  usually  partaking  of  the 
same  food. 

Commissure.    In  invertebrates,  a  nerve  connecting  two  ganglia  of  a  pair. 

Compound  eye.  An  arthropod  eye  which  is  composed  of  many  similar 
units,  called  ommatidia. 

Connecting  canal.  The  canal  which  joins  the  tube  foot  to  the  radial 
canal  of  an  echinoderm. 

Connective.  In  invertebrates,  a  nerve  connecting  two  ganglia  not  of  a 
pair. 

Contractile  vacuole.  Pulsating  ectoplasmic  organelle  present  in  fresh- 
water protozoa  and  commonly  absent  in  marine  forms.  It  dis- 
charges water  and  possibly  excretory  material. 

Copulation.  Union  for  the  purpose  of  transferring  spermatozoa  from 
male  to  female. 

Cormidium.  An  assemblage  of  structures  of  a  siphonophoran  colony 
consisting  of  a  hydrophyllium,  a  gastrozooid,  a  dactylozooid  and  a 
gonozooid. 

Coxa.    Basal  segment  of  the  leg  of  an  insect. 

Coxopod.     Basal  segment  of  the  protopod  in  Crustacea. 

Craspedote  medusa.    A  medusa  possessing  a  velum. 

Crop.    An  enlargement  of  the  alimentary  canal  for  storage  of  food. 

Crystalline  style.  A  transparent  rod  found  in  the  alimentary  canal  of 
many  polecypods. 

Ctenophoral  row.     A  row  of  swimming  plates  on  a  ctenophore. 

Cuticle.    Nonliving  external  layer  or  protective  covering. 

Cyst.  A  sac  or  pouch,  e.  g.,  as  in  the  larval  stage  of  tapeworms  or 
resting  condition  in  protozoa. 

Cysticercus.    A  stage  in  the  development  of  many  tapeworms. 

Dactylopod.    Terminal  segment  of  endopod  in  Crustacea. 

Dactylozooid.     Elongated  tentacle-like  zooid  of  a  coelenterate,  e.  g.,  a 

siphonophore. 
Denticle.    Small,  toothlike  protuberance,  as  in  the  buccal  cavity  of  some 

annelids. 
Dermal  branchiae.    Epithelial  projections  from  the  surface  of  the  body 

which  are  used  for  respiration  in  echinoderms. 
Development,  embryonic.     The  series  of  changes  which  lead  from  the 

fertilized  egg  to  the  mature  animal. 
Digestive  gland.     Any  gland  which  secretes  a  digestive  fluid. 
Dimorphism.    Two  distinct  forms  of  individuals  in  the  colony  or  species. 


256  GLOSSARY 

Dioecious.    Said  of  species  in  which  the  male  and  female  gonads  are  in 

separate  individuals. 
Directive  septa.    Those  placed  opposite  the  siphonoglyphs  of  an  actino- 

zoan. 
Disk.     In  a  starfish,  the  central  portion  from  which  the  arms  radiate. 
Dissepiment.     Septum. 
Distal.    Eemote  from  the  point  of  origin  or  attachment.     Converse  of 

proximal. 
Diverticulum.    An  outpocketing  from  a  tube,  a  caecum. 
Dorsal.    Pertaining  to  the  back. 
Dorsal  lamina.    A  ciliated  ridge  on  the  dorsal  side  of  the  pharynx  of 

an  ascidian. 
Dorsoventrally.    From  the  dorsal  to  the  ventral  position. 

Ectoderm.     The  outer  embryonic  or  germ  layer. 

Ectoparasite.    A  parasite  on  the  outside  of  the  body. 

Ectoplasm.     Outer  protoplasmic  layer  of  a  protozoan. 

Efferent.    Carrying  away,  as  a  vessel  which  leads  away  from  an  organ. 

Elytra.  The  modified  forewings  of  a  beetle;  the  scales  of  a  scale- 
worm. 

Embryo.    An  immature  organism. 

Encyst.     To  enclose  in  a  cyst. 

Endoderm.    The  inner  embryonic  or  germ  layer. 

Endoparasite.    A  parasite  inside  the  body. 

Endophragmal  skeleton.  Chitinous  plates  which  cover  the  nerve  chain 
and  ventral  blood  sinus  in  the  thorax  of  certain  crustaceans. 

Endoplasm.     Inner  protoplasmic  portion  of  a  protozoan. 

Endopod.  In  a  biramous  appendage  of  an  arthropod,  the  branch  which 
is  nearer  the  midline  of  the  body. 

Endoskeleton.    An  internal  skeleton. 

Endostyle.  A  ciliated  groove  in  the  ventral  wall  of  the  pharynx  of 
certain  primitive  chordates.    . 

Ephyra.  The  stage  which  follows  the  scyphistoma  in  the  development 
of  a  scyphomedusan.  It  consists  of  a  disklike  body  with  8  marginal 
notched  lobes. 

Epicardium.    A  hollow  process  from  the  pharynx  of  some  ascidians. 

Epipharynx.    In  some  insects,  a  projection  from  the  roof  of  the  mouth. 

Epiphysis.  A  plate  joined  to  the  base  of  the  alveolus  in  the  mouth 
parts  of  an  echinoid. 

Epipod.  A  membranous  projection  from  the  basipod  of  certain  crus- 
tacean appendages.    It  extends  into  the  gill  chamber. 

Episternum.  Among  invertebrates,  a  lateral  piece  next  to  the  sternum, 
as  in  arthropods. 


GLOSSARY 


257 


Epistome.    A  projection  above  the  mouth  as  in  Pectinatella. 
Esophagus.    The  portion  of  the  alimentary  canal  which  leads  back  from 

the  buccal  cavity  or  pharynx. 
Euglenoid.     Similar  to  Euglena,  especially  in  movements. 
Exopod.    The  branch  of  the  biramous  appendage  of  an  arthropod  which 

is  away  from  the  midline  of  the  body. 
Exoskeleton.    An  outer  covering,  as  a  shell. 
Exumbrella.     The  convex  or  aboral  side  of  a  medusa. 
Eye  spot.    A  pigment  spot  generally  supposed  to  be  photoreceptive. 

Femur.  In  an  insect  appendage,  the  third  segment  from  the  body  of 
the  animal. 

Fission.    Eeproduction  by  division. 

Flagellum.     An  elongated,  protoplasmic,  motile  process  of  a  cell. 

Flame  cell.  An  excretory  cell  characteristic  of  certain  invertebrates, 
e.  g.,  platyhelminthes,  nemertines,  rotifers  and  certain  polychaetes. 
It  possesses  a  cavity  continuous  with  the  lumen  of  the  excretory 
duct.    This  cavity  may  contain  a  bundle  of  cilia  or  a  flagellum. 

Food  vacuole.  In  Protozoa,  a  temporary  space  in  which  food  is  di- 
gested. 

Foot.  Among  invertebrates,  a  locomotor  organ  characteristic  of  mol- 
luscs. 

Funiculus.  A  strand  of  tissue  which  connects  the  stomach  with  the 
body  wall  in  Bryozoa. 

Funnel.  The  tube  through  which  water  is  expelled  from  the  mantle 
chamber  by  cephalopods. 

Ganglion.    A  group  of  nerve  cells. 

Gastric  filament.     One  of  the  filaments  in  the  digestive  cavity  of  Scy- 

phozoa. 
Gastrovascular.     Digestive  and  circulatory  in  function,  as  the  gastro- 

vascular  cavity  or  coelenteron  of  coelenterates. 
Gastrozooid.    Feeding  individual  in  a  hydrozoan  colony. 
Genital  atrium.     A  cavity  receiving  the  genital  ducts,  as  in  Bdelloura. 
Genital  gland.     A  gonad. 
Genital  plate.     One  of  the  plates  bearing  the  external  openings  of  the 

genital  ducts  in  echinoderms. 
Genital  pore.     The  external  opening  of  a  genital  duct  as  in  the  genital 

plate. 
Gill.     Aquatic  respiratory  organ. 

Gizzard.    A  heavy,  muscular,  grinding  division  of  the  alimentary  canal. 
Gonad.     A  gland  which  produces  sex  cells. 
Gonangium.    See  Gonotheca. 

17 


258  GLOSSARY 

Gonophore.  In  coelenterates,  the  specialized  form  which  produces  the 
sex  cells;  whether  a  free-swimming  medusa  or  any  of  the  various 
intermediate  stages  between  it  and  the  sporosac. 

Gonosome.  The  assemblage  of  structures  directly  connected  with  sexual 
reproduction  in  hydroids.  The  comprehensive  term  which  includes 
gonophores,  blastostyles,  ovaries,  gonangia,  etc. 

Gonotheca.  The  chitinous  covering  of  a  gonozooid  in  calyptoblastic 
hydroids. 

Gonozooid.     The  reproductive  zooid  in  coelenterates. 

Green  gland.  In  certain  crustaceans,  a  paired  excretory  gland,  the  duct 
of  which  opens  to  the  outside  at  the  base  of  the  second  antenna. 

Gullet.     Esophagus. 

Gut.     Digestive  tube. 

Gymnoblastic.     Lacking  hydrothecae  and  gonothecae. 

Head.  The  more  or  less  differentiated  anterior  end  in  bilaterally  sym- 
metrical animals. 

Hepatic  caeca.  Digestive  glands  opening  in  the  stomach  in  certain 
echinoderms. 

Hermaphrodite.  An  individual  in  which  both  male  and  female  gonads 
are  present. 

Holophytic.     The  nutrition  characteristic  of  green  plants. 

Holozoic.     The  nutrition  characteristic  of  animals. 

Homologous.     Of  similar  structure  or  origin. 

Host.     The  organism  which  harbors  a  parasite. 

Hyaline.     Transparent,  glassy. 

Hydranth.     An  individual  of  a  hydroid  colony. 

Hydrocaulus.     The  stem  of  a  hydroid  colony. 

Hydrophyllium.  A  disk-shaped  protective  structure  covering  other 
parts  of  the  cormidium  in  a  siphonophore. 

Hydrorhiza.     The  rootlike  attachment  of  a  hydroid  colony. 

Hydrotheca.  The  chitinous  covering  of  a  vegetative  hydranth  in 
calyptoblastic  hydroids. 

Hypodermis.  The  single-layered  integument  in  invertebrates  possess- 
ing a  cuticle. 

Hypopharynx.  A  projection  borne  on  the  lower  side  of  the  pharynx  of 
some  insects. 

Hypostome.    In  a  rrydranth,  the  projection  which  bears  the  mouth. 

Incurrent  canal.    A  canal  that  admits  water  to  a  sponge. 
Integument.     Outer  covering  of  an  animal. 

Interambulacral  area.  One  of  the  areas  of  an  echinoderm  which  lies 
between  adjacent  ambulacral  areas. 


GLOSSARY  259 

Interfilamentar    junction.      A    connection    between    adjacent    filaments 

in  a  pelecypod  gill. 
Interlamellar  junction.     A  connection  between  adjacent  lamellae  in  a 

pelecypod  gill. 
Internode.    In  hydroids,  that  portion  of  a  stem  or  branch  between  two 

branches. 
Inter-radial    canals.      In    a    medusa,   the    canals   which   run   from    the 

stomach  to  the  circular  canal  and  which  lie  midway  between  the 

per-radial  canals. 
Introvert.    A  portion  which  may  be  drawn  in,  as  the  anterior  end  of 

Phascolosoma. 
Ischiopod.     The  first  segment  of  a  crustacean  endopod. 

Kidney.  Frequently  but  improperly  applied  to  the  excretory  organ  of 
an  invertebrate. 

Labrum.  The  fused  pair  of  appendages  which  forms  the  lower  lip  of 
insects  and  some  other  arthropods. 

Lamella.  One  of  the  two  sides  which  form  a  pelecypod  gill;  a  flat 
structure. 

Lamelliform.    Like  a  lamella;  thin  and  flat. 

Lamina.    A  thin  plate  or  a  scale. 

Lancet.    A  sharp  structure;  a  portion  of  the  sting  of  a  bee. 

Larva.    An  embryo;  a  stage  in  the  development  of  an  animal. 

Lateral.    At  or  toward  the  side. 

Ligament.    In  pelecypods,  the  elastic  structure  which  unites  the  valves. 

Lithite.    One  of  the  concretions  in  a  tentaculocyst  of  a  medusa. 

Liver.  Frequently  but  improperly  applied  to  the  largest  digestive 
gland  of  many  invertebrates. 

Lophophore.  The  disk  which  surrounds  the  mouth  and  bears  the  ten- 
tacles in  the  Molluscoida. 

Lorica.     The  transparent  covering  of  a  rotifer. 

Macronucleus.  In  general,  the  larger  of  the  two  nuclei  of  ciliate  Pro- 
tozoa. 

Madreporic  plate.  The  perforated  plate  through  which  the  water- 
vascular  system  of  an  echinoderm  communicates  with  the  outside. 

Mandible.    One  of  a  pair  of  mouth  appendages  in  arthropods. 

Mandibulate.    Possessing  mandibles. 

Mantle.  The  outer  fold  of  the  body  of  many  molluscs;  the  entire  body 
wall  in  tunicates.    In  both  groups  it  secretes  a  protective  covering. 

Manubrium.    The  hollow  outgrowth  supporting  the  mouth  of  a  medusa. 


260  GLOSSARY 

Marginal  lappets.  Small  flaps  of  tissue  near  the  sense  organs  of  Dis- 
comedusae. 

Mastax.  In  rotifers,  the  very  active  muscular  grinding  part  of  the  di- 
gestive tract. 

Maxilla.     One  of  the  mouth  appendages  of  arthropods. 

Medusa.    Jelly  fish;  the  sexual  stage  of  certain  coelenterates. 

Membranelles.  Organelles  formed  of  a  double  row  of  fused  cilia  found 
in  some  cilates. 

Meropod.  The  second  segment  from  the  base  of  the  endopod  of  a 
crustacean. 

Mesenteric  filament.  In  Actinozoa,  the  thickened  free  edge  of  certain 
mesenteries.     Gland  cells  and  nettle  cells  are  present  here. 

Mesentery.  A  membrane  which  supports  the  intestine.  In  Actinozoa, 
a  membranous  lamella  or  sheetlike  portion  having  mesoglea  for 
its  middle  layer  and  covered  on  either  face  by  endoderm. 

Mesoglea.  The  jelly-like  substance  which  separates  the  ectoderm  and 
endoderm  of  a  coelenterate. 

Metagenesis.     In  animals,  alternation  of  generations. 

Metamere.  One  of  the  serial  body  segments  of  an  animal,  as  in  an- 
nelids. 

Metamorphosis.  In  animals,  a  change  in  structure,  as  from  larval  to 
adult  stage. 

Metapleural  fold.     One  of  a  pair  of  folds  on  the  sides  of  Amphioxus. 

Micronucleus.    In  general,  the  smaller  of  the  two  nuclei  in  ciliates. 

Moniliform.    Resembling  a  string  of  beads. 

Monoecious.  Said  of  species  in  which  the  male  and  female  gonads  are 
present  in  the  same  individual. 

Mouth.     The  opening  through  which  food  is  taken. 

Myoneme.    A  contractile  fiber,  as  in  Vorticella. 

Nacre.    The  innermost  layer  of  a  mollusc  shell. 

Nematocyst.     The  stinging  organ  contained  in  the  cnidoblast. 

Nephridiopore.     The  external  opening  of  a  nephridium. 

Nephridium.     Excretory  tubule. 

Nephrostome.     The  opening  from  the  coelom  into  a  nephridium. 

Nerve  connective.  In  invertebrates,  a  nerve  connecting  two  ganglia 
not  of  a  pair. 

Nettle  cell.    Cnidoblast. 

Neuropodium.     The  ventral  division  of  a  parapodium  of  an  annelid. 

Nidamental  gland.  In  certain  molluscs,  an  accessory  reproductive 
gland  possessed  by  females. 

Notochord.  A  dorsal,  living,  internal,  supporting  structure  characteris- 
tic of  Chordata. 

Notopodium.    The  dorsal  division  of  a  parapodium  of  an  annelid. 


GLOSSARY  261 

Odontophore.  A  special  structure  in  the  mouth  of  most  mollusca  ex- 
cept pelecypods.  The  name  is  applied  to  the  whole  structure,  car- 
tilage, radula  and  muscles.  (It  is  used  by  some  authors  as  the 
equivalent  of  radula.) 

Ocellus.    A  simple  eye  of  an  arthropod. 

Ocular  plate.  In  echinoderms,  a  plate  at  the  end  of  an  ambulacral 
area. 

Olfactory  organ.     An  organ  to  distinguish  odors. 

Ooecium.    A  structure  in  Bryozoa  in  which  the  embryo  develops. 

Ootype.  The  region  in  flat  worms  where  the  eggs  are  supplied  with 
shells. 

Operculum.  The  horny  lid  which  fits  into  the  aperture  of  the  shell  of 
some  gastropods.  A  chitinous  protective  structure  on  the  hydro- 
theca  of  certain  hydroids  which  closes  the  hydrothecal  aperture 
when  the  hydranth  is  retracted. 

Oral.    Pertaining  to  the  mouth. 

Organelle.  A  specialized  part  of  a  cell,  as  a  cirrus,  performing  func- 
tions analogous  to  those  of  the  organs  of  metazoa. 

Osculum.    The  opening  of  a  sponge  through  which  water  escapes. 

Osphradium.  A  structure  in  the  gill  region  of  aquatic  molluscs  and 
supposedly  of  sensory  function. 

Ossicle.    A  small  hard  plate. 

Ostium.  A  small  pore;  in  pelecypod  gills,  one  of  the  pores  through 
which  water  is  passed.  In  sponges,  the  opening  through  which 
water  enters  an  incurrent  canal. 

Otocyst.     A  statocyst. 

Otolith.     Statolith. 

Ovary.    A  gonad  which  produces  eggs. 

Oviducal  gland.     A  glandular  portion  of  an  oviduct,  as  in  the  squid. 

Oviduct.  In  a  female,  a  duct  which  carries  eggs  to  the  uterus  or  the 
exterior. 

Ovipositor.     In  some  insects,  an  elongate  structure  used  in  depositing 

eggs. 
Ovum.     Egg. 

Pallial  line.     The  depression  in  the  shell  of  a  pelecypod  at  the  point 

of  attachment  of  pallial  muscles. 
Pallial  sinus.     The  indentation  in  the  pallial  line  of  some  pelecypods 

at  the  point  of  insertion  of  the  retractor  muscles  of  the  siphons. 
Palp.     A  process  near  the  mouth.     It  occurs  in  several  invertebrate 

groups:    e.  g.,  in  polychaete  annelids,  one  of  a  pair  of  processes  on 

the   ventral   side   of   the   prostomium;    in   pelecypods,  one   of   four 

fleshy  processes  around  the  mouth. 


262  GLOSSARY 

Papilla.     A  small  projection. 

Paragnatha.    Lamellae  behind  the  mandibles  of  some  Crustacea. 

Parapodium.  Typical  annelid  appendage.  Usually  one  pair  per  seg- 
ment. 

Parenchyma.  Any  soft  tissue;  specifically,  the  tissue  occupying  much 
of  the  space  between  the  body  wall  and  digestive  tract  in  a  flat 
worm . 

Pectine.    One  of  a  pair  of  appendages  of  scorpions. 

Pedicel.     The  stalk  supporting  a  hydranth  or  gonozooid. 

Pedicellaria.  A  minute  pincer-like  organ  which  is  present  on  As- 
teroidea  and  Echinoidea. 

Pedipalpi.  The  second  pair  of  appendages  in  arachnids.  They  lie 
on  each  side  of  the  mouth. 

Peduncle.    A  short  stalk. 

Pelagic.  Said  of  organisms  which  live  at  or  near  the  surface  of  the 
water. 

Pen.    Vestigial  internal  shell  of  a  cephalopod,  as  in  the  squid. 

Penis.    Male  intromittent  organ. 

Pericardium.     The  membrane  surrounding  the  heart. 

Pereiopod.     The  walking  leg  of  a  crustacean. 

Peripharyngeal  bands.  The  ciliated  bands  situated  in  the  anterior 
region  of  the  pharynx  and  connecting  the  endostyle  with  the  dorsal 
lamina  in  many  protochordates. 

Periproct.  The  region  around  the  anus  (especially  applied  to  the 
echinoderms). 

Perisarc.     The  chitinous  covering  of  the  coenosarc  in  hydroids. 

Peristalsis.  The  motion  caused  by  the  relaxation  and  contraction  of 
the  muscle  fibers  in  the  walls  of  a  tube. 

Peristome.  The  region  around  the  mouth  (especially  applied  to  echino- 
derms) . 

Peristomium.     The  first  somite  of  an  annelid.    In  it  the  mouth  lies. 

Peritoneum.     The  membrane  which  lines  the  coelom. 

Per-radial  canals.  In  a  medusa,  the  canals  which  run  from  the  stomach 
to  the  circular  canal  and  which  lie  opposite  the  corners  of  the 
mouth. 

Pharynx.     An  anterior  division  of  the  alimentaiy  canal. 

Planula.  A  young  ciliated,  free-swimming  coelenterate  embryo  con- 
sisting of  two  cell  layers. 

Pleopod.    Any  abdominal  appendage  of  a  crustacean. 

Pleurobranch.     A  crustacean  gill  which  is  borne  on  the  body  wall. 

Pleuron.  One  of  the  lateral  pieces  or  processes  of  a  somite  of  an  ar- 
thropod. 

Podobranch.  A  crustacean  gill  which  is  borne  on  the  basal  joint  of  an 
appendage. 


GLOSSARY 


263 


Polymorphism.  Many  distinct  forms  of  individuals  within  a  single 
species. 

Polyp.    An  individual  of  a  hydroid  stage  of  a  coelenterate. 

Postcava.  In  some  invertebrates,  a  blood  vessel  which  leads  to  the 
heart  from  the  posterior  portion  of  the  body,  as  in  the  squid. 

Posterior.     Hinder;  anal  end. 

Precava.  In  some  invertebrates,  a  blood  vessel  which  leads  to  the 
heart  from  the  anterior  end  of  the  body. 

Primary  mesentery.  A  mesentery  which  extends  from  the  body  wall 
to  the  actinopharynx  in  Actinozoa. 

Proboscis.  Applied  to  various  tubelike  organs  around  the  head  some- 
times capable  of  being  everted  or  protruded. 

Proglottid.  One  of  the  numerous  "segments"  which  are  formed  by  the 
scolex  and  which,  together  with  the  scolex,  make  up  a  tapeworm. 

Propod.  The  next  to  the  last  segment,  fourth,  of  a  typical  crustacean 
endopod. 

Prosopyle.  One  of  the  pores  through  which  water  passes  from  an  in- 
current  to  a  radial  canal  in  most  sponges. 

Prostomium.  The  anterior  process  which  overhangs  the  mouth  of  an 
annelid. 

Prothorax.    Anterior  division  of  the  thorax  of  an  insect. 

Protomerite.     The  anterior  part  of  a  eugregarine,  e.  g.,  Gregarina. 

Protopod.  The  basal  portion  of  a  crustacean  appendage.  It  consists 
of  two  segments,  a  basal  coxopod  and  a  distal  basipod.  The  latter 
frequently  bears  both  an  exopod  and  an  endopod.  In  some  cases 
it  also  bears  an  epipod  or  bract  and  a  gill. 

Proximal.  Nearest  to  the  point  of  origin  or  attachment.  Converse  of 
distal. 

Pseudopodium.  A  temporary  protrusion  of  the  protoplasm  of  a  cell. 
Found  in  all  Sarcodina  and  in  certain  tissue  cells  of  higher  animals. 

Pyloric  stomach.     Posterior  or  second  division  of  the  stomach. 

Radially  symmetrical.     The  condition  of  having  similar  parts  radially 

arranged  about  a  central  axis;  as  in  a  jelly  fish. 
Radius.     One  of  the  parts  of  the  jaw  apparatus  of  an  echinoid;  from 

center  to  periphery. 
Radula.     The  flexible,  tooth-bearing,  ribbon-like  membrane  of  an  odon- 

tophore. 
Ray.    One  of  the  arms  of  a  starfish  or  a  brittle  star. 
Rectum.     The  posterior  division  of  the  alimentary  canal. 
Renal  organ.     An  organ  which  excretes  nitrogenous  wastes  and  other 

materials. 
Reservoir.    The  place  where  anything  is  stored;  the  poison  sac  of  a  bee. 


264  GLOSSARY 

Respiratory   tree.     The   respiratory   mechanism   of   some   holothurians, 

opening  into  the  cloaca. 
Retractor  muscle.     A  muscle  that  withdraws  an  organ  or  part  of  an 

animal. 
Root  stalk.    A  creeping  stem  from  which  the  hydrocauli  originate. 
Rostrum.    The  anterior  spine  of  a  lobster  and  of  other  crustaceans. 
Rotula.     One  of  the  calcareous  pieces  of  the  jaw  of  an  echinoid. 
Rudimentary.      When    applied    to    adult    animals,    means   permanently 

undeveloped;  vestigial. 

Sagittal  plane.  The  median  plane,  i.  e.,  that  which  divides  a  bi- 
laterally symmetrical  animal  into  two  equivalent  halves. 

Salivary  gland.  In  invertebrates,  any  gland  which  opens  into  the 
mouth  cavity. 

Scaphognathite.  The  flattened  structure  composed  of  the  fused  endo- 
pod  and  epipod  of  the  second  maxilla  of  certain  Crustacea.  It  is 
used  to  expel  water  from  the  branchial  cavity. 

Schizogony.     Spore  formation  of  the  type  characteristic  of  schizonts. 

Schizonts.  In  Sporozoa  a  cell,  formed  by  the  growth  of  a  sporozoite 
(merozoite)  in  a  cell  or  corpuscle  of  the  host,  which  forms  mero- 
zoites  by  sporulation  (multiple  fission). 

Schizopod.     A  biramous  arthropod  appendage. 

Scolex.  Anterior  or  attaching  portion  of  the  tapeworm  from  the  pos- 
terior end  of  which  the  proglottids  are  formed. 

Scyphistoma.  The  attached,  hydra-like  larval  stage  of  many  Scy- 
phozoa. 

Segment.  One  of  a  series  of  divisions  of  an  animal's  body  or  appendage. 
In  the  former  case  it  is  synonj^mous  with  somite. 

Segmentation,     (a)   Cleavage;    (6)   division  of  body  into  segments. 

Seminal  receptacle.     A  sac  in  which  spermatozoa  are  stored. 

Seminal  vesicles.     The  sacs  which  inclose  the  testes  of  an  earthworm. 

Septum.  A  plate  which  divides  two  spaces.  In  annelids  the  partition 
which  separates  the  coelomic  cavities  of  adjacent  segments. 

Sessile.  Attached;  without  the  power  of  locomotion.  Also  applied  to 
hydranths  without  a  stalk. 

Seta.  A  stiff,  slender,  bristle-like  structure.  Most  commonly  applied 
to  one  of  the  chitinous  bristles  imbedded  in  the  body  wall  or 
parapodium  of  an  annelid. 

Setigerous  gland.  An  integumentary  gland  which  forms  setae.  Typi- 
cally two  pairs  per  segment. 

Shell  gland.  A  gland  which  secretes  the  egg  shell;  sometimes  applied 
to  the  excretory  organs  of  Entomostraca. 


GLOSSARY 


265 


Siphon.  One  of  the  two  tubes  concerned  with  the  passage  of  water 
through  a  mollusc  or  a  tunicate.  Water  enters  through  the  in- 
current  siphon  and  flows  out  through  the  excurrent  siphon. 

Siphonoglyph.  The  ciliated  groove  leading  into  the  actinopharynx 
from  a  corner  of  the  mouth. 

Somite.    Metamere;  one  of  the  serial  body  segments  of  an  animal. 

Sperm.     Spermatozoon;  male  reproductive  cell. 

Spermary.     A  temporary  sperm-producing  organ;  a  testis. 

Spermatheca.  A  seminal  receptacle,  used  for  storing  spermatozoa  in 
the  female. 

Spermatophore.     A  specially  formed  packet  of  spermatozoa. 

Spermatozoon.     Male  reproductive  cell. 

Sperm  sphere.    A  mass  of  spermatozoa  in  the  earthworm. 

Spicules.    Minute  skeletal  bodies  characteristic  of  sponges. 

Spinneret.  One  of  the  organs  by  means  of  which  a  spider  spins  its 
thread. 

Spiracle.    Breathing  pore;  external  opening  of  the  tracheal  system. 

Spiral  valve.  The  spirally  wound  internal  fold  of  the  wall  of  the  in- 
testine in  elasmobranchs  and  certain  other  fishes. 

Spongin.  The  specialized  spicule  material  of  which  the  fibers  of  the 
commercial  sponges  are  composed. 

Spore.  In  animals,  especially  Protozoa,  a  cell,  the  product  of  multiple 
fission,  which  is  capable  of  developing  into  a  new  organism. 

Sporoblasts.     In  sporozoa,  a  cell  which  divides  into  sporozoites. 

Sporogony.  Eeproduction  by  multiple  fission  (sporulation).  Specifi- 
cally, in  Sporozoa,  spore  formation  by  a  zygote  after  encystment. 

Sporont.     The  detached  stage  of  Gregarina. 

Sporosac.  In  coelenterates,  a  sac  which  contains  the  generative  cells— 
an  undeveloped,  possibly  degenerate  medusa. 

Sporozoite.  In  Sporozoa,  a  small,  usually  elongate,  sickle-shaped  or 
ameboid  spore  produced  after  zygote  formation. 

Sporulation.     The  act  of  forming  spores;  multiple  fission. 

Stalk.     A  stem  or  a  peduncle. 

Statoblast.     Asexual  reproductive  body  of  certain  Bryozoa. 

Statocyst.    An  organ  of  equilibrium  present  in  many  invertebrates. 

Statolith.    The  body  or  bodies  present  within  the  cavity  of  a  statocyst. 

Sternum.    The  ventral  covering  of  a  segment  of  an  arthropod. 

Stigma.  In  insects,  one  of  the  external  openings  of  the  trachea;  one 
of  the  apertures  in  the  pharynx  of  an  ascidian. 

Stolon.    An  extension  of  the  body  wall  from  which  buds  are  developed. 

Stomach.     In  invertebrates,  the  storage  (food)  division  of  the  alimen- 
tary canal. 
Stomach-intestine.    A  division  of  the  alimentary  canal  which  functions 
as  both  stomach  and  intestine,  as  in  the  earthworm. 


266  GLOSSARY 

Stomodaeum.     The  anterior  portion  of  the  alimentary  canal  which  is 

ectodermal  in  origin. 
Stone  canal.     The  tube  which  leads  from  the  madreporic  plate  to  the 

circular  water  canal  in  echinoderms. 
Stylet.    A  small,  sharp  instrument. 
Subgenital   Pits.      The    pouches  adjacent   to   the    gonads   of   the   Dis- 

comedusae,  on  the  subumbrellar  side. 
Subumbrella.     The  concave  or  oral  side  of  a  medusa. 
Sulcus.     A  furrow  or  groove. 

Suture.    An  immovable  union  between  plates  or  ossicles. 
Swimmeret.     Pleopod;  any  abdominal  appendage  of  a  crustacean. 
Swimming  plate.    One  of  the  ciliated  swimming  organs  of  a  ctenophore. 
Synchronous.     Happening  at  the  same  time. 

Tactile.    Capable  of  feeling. 

Tarsus.     The  segmented  foot  of  an  insect. 

Telson.  Hinder  division  of  a  crustacean,  usually  not  considered  a  seg- 
ment. 

Tentacle.  An  elongated,  tactile  organ,  usually  unsegmented.  In  poly- 
chaetes,  a  prostomial  structure  usually  arising  from  the  anterior 
end  and  more  dorsal  than  the  palps. 

Tentaculocyst.    A  marginal  sense  organ  in  certain  medusae. 

Tergum.    The  dorsal  covering  of  a  segment  of  an  arthropod. 

Test.  Hard  or  firm  outer  covering  as  the  shells  of  many  protozoa, 
echinoderms,  molluscs,  etc.,  and  the  tunics  of  Urochorda. 

Testis.     Sperm-producing  organ. 

Thorax.  The  body  division  of  arthropods  between  the  head  and  ab- 
domen. 

Tibia.  In  an  insect  leg,  the  segment  lying  between  the  femur  and  the 
tarsus. 

Trachea.     One  of  the  respiratory  tubes  of  certain  arthropods. 

Trichocyst.  An  ectoplasmic  organelle,  often  considered  as  offensive  or 
defensive  in  function,  formed  in  many  holotrichous  ciliates. 

Trivium.  The  three  rays  of  a  starfish  which  are  farthest  from  the 
madreporic  plate. 

Trochal  disk.     The  ciliated  disk  of  a  rotifer. 

Trochanter.  In  an  insect  leg,  the  second  segment  from  the  body  of 
the  animal. 

Trochophore.  The  free-swimming  larva,  with  bands  of  cilia,  especially 
typical  of  the  annelids  and  Mollusca. 

Trochosphere.     Trochophore. 

Tubercle.    A  small  knoblike  prominence. 

Tunic.     The  outer  covering  of  an  ascidian. 


GLOSSARY  267 

Tunicin.     A    cellulose-like   substance   found    in   the   tunics   of    certain 

Urochorda. 
Typhlosole.     A  longitudinal  internal  fold  in  the  wall  of  the  intestines 

of  some  invertebrates,  e.  g.,  the  earthworm. 

Umbo.  In  the  valve  of  a  clam  shell,  the  raised  portion  which  ends 
in  the  beak.    It  is  the  first  part  of  the  shell  to  be  formed. 

Umbrella.  The  umbrella-shaped  major  portion  of  the  body  of  a  jelly 
fish. 

Uriniferous  tube.     One  of  the  tubes  of  an  excretory  organ. 

Uropod.     One   of   the   pair  of  broad,   leaflike   appendages   of  the   last 

abdominal  segment  of  a  crustacean. 

Uterus.    A  female  organ  in  which  young  develop. 

f 

Vagina.     In  invertebrates,  the  terminal  division  of  the  female  repro- 
ductive duct. 
Vas  deferens.    The  duct  which  leads  away  from  the  testis. 
Velum.     The  ledgelike,  delicate,  muscular  membrane  extending  inward 

from  the  subumbrellar  margin  of  certain  jelly  fishes. 
Ventral.     Under  surface;  belly. 

Ventricle.    A  division  of  the  heart  which  forces  blood  to  the  body. 
Ventriculus.     In   insects,   the  division   of  the   alimentary   canal  which 

leads  into  the  stomach. 
Vestibule.     A   depression   near  the   mouth   in   certain   Protozoa   as  in 

Vorticella. 
Vestigial.    An  organ  which  remains  undeveloped  and  has  no  function; 

rudimentary  as  applied  in  anatomy. 
Viscera   (sing.,  Viscus).     Internal  organs  taken  collectively. 
Visceral  mass.     Applied  to  the   portion  of   a  mollusc  which   contains 

stomach,  intestine,  liver,  gonads,  etc. 
Vitellarium.     A  female  reproductive  gland  which  supplies  cells  to  be 

used  as  food  for  developing  embryos,  as  in  Bdelloura. 
Vitelline  glands.    Same  as  vitellarium. 

Water  tube.     One  of  the  tubes  between  the  lamellae  of  a  pelecypod 

gill. 
Whorl.     One  of  the  turns  of  a  gastropod  shell. 

Yolk  mass.     A  mass  of  food  material  for  the  nourishment  of  an  em- 
bryo. 

Zoophyte.     An  animal  which  is  somewhat  plantlike  in  appearance. 
Zooid.     One  of  the  more  or  less  independent  individuals  which  go  to 

make  up  an  animal  colony  as  in  Obelia  and  Bugula.    Zooids  may 

be  nutritive,  reproductive,  defensive,  or  sensory. 


INDEX 


References  to  directions  for  the  study  of  forms  are  indicated  by  the  use  of 

bold-faced  type  for  the  page  number. 


ACANTHOCEPHALA,  79 

Acarina,  166 
Acineta,  19 
Acinetaria,  19 
Acmaea,  123 
Acnidosporidia,  20 
Acridium,  200 
Actiniaria,  42 
Actinomyxida,  20 
Actinophrys,  18,  24 
Actinopoda,  18 
Actinosphaerium,  18,  24 
Actinotrocha,  231 
Actinozoa,  42,  59 
Adelea,  20 
Adeleida,  20 
Aeginopsis,  41 
Aeolis,  123 
Agalena,  166 
Alcyonacea,  42 
Alcyonaria,  42,  61 
Alcyonium,  42 
Alectrion,  143 
Algae,  21 

Amaroucium,  232,  240 
Amoeba,  18,  22 
Amoebaea,  18 
Amphineura,  122,  142 
Amphioxus,  232,  243 
Amphipoda,  166 
Amphitrite,  90,  100 
Annelida,  90 
Anoplodactylus,  166 
Anostraca,  165 


Antedon,  212 
Anthomedusae,  41 
Antipatharia,  42 
Apis,  206 
Aplacophora,  123 
Aplysina,  36 
Apoda,  212 
Appendicular  a,  232 
Appendix,  245 
Apus,  165 

Arachnida,  166,  189 
Araneida,  166 
Arbacia,  211,  220 
Arcella,  18,  23 
Archi-annelida,  90 
Archi-chaetopoda,  90 
Arenicola,  90,  102 
Argonauta,  124 
Argulus,  187 
Armata,  90 
Artemia,  165 
Arthropoda,  165 
Articulata,  86 
Ascaris,  79 
.Ascidiacea,  232 
Ascidian,  234 
Aspidobranchia,  123 
Asterias,  211,  212 
Asteroidea,  211,  212 
Astrangia,  42,  61 
Astropecten,  211 
Astrophyton,  211 
Aurelia,  42,  55 
Autolytus,  90,  95 

269 


270 


INDEX 


Babesia,  20 

Babesiina,  20 

Balanoglossus,  231,  233 

Balanus,  165 

Barnacle,  188 

Bdelloura,  66,  68 

Beach-flea,  182 

Bee,  206 

Beetle,  201 

Beroe,  63 

Beroida,  63 

Blue  crab,  175 

Bodo,  17 

Botryllus,  232,  239 

Bougainvillia,  41,  52 

Brachionus,  84 

Brachiopoda,  86,  89 

Branchiopoda,  165 

Branchipus,  185 

Bryozoa,  86 

Buccinum,  123 

Bug,  203 

Bugula,  86 

Bulla,  123 

Busycon,  70,  123,  143,  157 

Buthus,  166,  195 

Butterfly,  203,  208 


Calcakea,  36 
Callinectes,  166,  175 
Calyptoblastea,  41 
Cambarus,  165 
Campanularia,  41,  47 
Cancer,  166 
Caprella,  166,  184 
Carchesium,  19 
Caryophyllaeus,  66 
Centipede,  199 
Cephalochorda,  232,  243 
Cephalodiscus,  231 
Cephalopoda,  123,  153 
Ceratium,  21,  34 
Cercomonas,  17 


Cerebratulus,  66,  77 
Cestida,  63 
Cestoda,  66,  73 
Cestus,  63 
Chaetognatha,  79 
Chaetopleura,  122,  142 
Chaetopoda,  90,  91 
Chaetopterus,  90,  99 
Chalina,  36,  40 
Charybdea,  42 
Chelifer,  166 
Chilopoda,  166 
Chiton,  122,  142 
Chloridella,  165,  181 
Chonotricha,  19 
Chordata,  231 
Chthamalus,  165 
Ciliata,  18 
Ciona,  232 
Cirripathes,  42 
Cirripedia,  165 
Cistenides,  101 
Cladocera,  165 
Clam,  137,  138 
Clam-worm,  91 
Clathrulina,  18,  25 
Clava,  41 
Clearing,  248 
Clepsine,  91 
Cliona,  36,  40 
Clymenella,  90,  101 
Clypeastroidea,  211 
Cnidosporidia,  20 
Coccidiida,  20 
Coccidiomorpha,  20 
Coelenterata,  41 
Coleoptera,  167 
Coleps,  18 
Colpidium,  18 
Copepoda,  165 
Corticella,  36 
Crab,  175,  179 

horseshoe,  189 
Crago,  166 


INDEX 


271 


Craspedota,  49 
Crayfish,  167 
Crepidula,  123 
Crinoidea,  212 
Crisia,  86 

Crossobothrium,  66,  74 
Crustacea,  165,  167 
Cryptocotyle,  73 
Cryptozonia,  211 
Ctenophora,  63 
Cubomedusae,  42 
Cucumaria,  212 
Cumingia,  141 
Cuspidaria,  122 
Cyanea,  42,  59 
Cyclops,  165,  186 
Cydippida,  63 
Cypris,  165 

Dactylometra,  59 
Daphnia,  165,  186 
Decapoda  (Arthropoda),  165 

(Mollusca),  123 
Dehydrating,  246 
Deiopea,  63 
Demospongiae,  36 
Dentalium,  123 
Dermacentor,  166 
Dibranchiata,  123 
Dictyonina,  36 
Didinium,  18 
Difflugia,  18,  23 
Digenetica,  66 
Dinoflagellida,  21 
Dinophilea,  84 
Dinophyceae,  21 
Diopatra,  90,  98 
Diplopoda,  167 
Diptera,  167 
Discomedusae,  42 
Distomum,  66 
Dolichoglossus,  231,  233 
Doliolum,  232 
Dondersia,  123 


Earthworm,  109 
Earwig,  199 
Echinarachnius,  211 
Echinodermata,  211 
Echinoidea,  211,  220 
Echinorhynchus,  79 
Echiurus,  90 
Ectoprocta,  86 
Eimeria,  20 
Eimeriina,  20 
Elasipoda,  212 
Emerita,  166,  180 
Ensis,  140 

Enteropneusta,  231,  233 
Entoprocta,  86 
Epeira,  166,  196 
Ephelota,  19,  30 
Epistylis,  19 
Erichsonella,  166 
Eudendrium,  41 
Euglena,  21,  32 
Euglenida,  21 
Eugleninae,  21 
Eugregarinida,  19 
Eulamellibranchia,  122 
Euplectella,  36 
Euplotes,  19,  29 
Eurete,  36 
Euryalida,  211 
Euspongia,  36 
Euthyneura,  123 

Fairy  shrimp,  185 
Favia,  61 
Filibranchia,  122 
Fish-louse,  187 
Fixing,  246 
Flustrella,  86,  88 
Fly,  203 

Foraminifera,  18,  23 
Fresh-water  mussel,  124 

polyp,  43 
Frontonia,  18 
Fulgur  (Busycon),  143 


272 


INDEX 


Galeodes,  166 
Gammarus,  166 
Gastropoda,  123,  143 
Gastrotricha,  84 
Gephyrea,  90,  119 
Giardia,  17 
Globigerina,  18 
Glossary,  251 
Glossiphonia,  91 
Gnathobdellida,  91 
Goat  shrimp,  184 
Gonionemus,  41,  48 
Goose  barnacle,  188 
Gordius,  79 
Gorgonacea,  42 
Gorgonia,  42,  61 
Grantia,  37 
Grasshopper,  200 
Gregarina,  19,  31 
Gregarinina,  19 
Gymnoblastea,  41 
Gymnolaemata,  86 


Haliotus,  123 
Halteria,  19 
Heliozoa,  18 
Helix,  123 
Hemichorda,  231 
Hemiptera,  167 
Hemosporidia,  20 
Hermit  crab,  179 
Heterocoela,  36 
Heteromysis,  182 
Heterotrichida,  19 
Hexactinellida,  36 
Hirudinea,  90 
Hirudo,  91 

Holothuroidea,  211,  226 
Holptricha,  18 
Homarus,  165,  167 
Homocoela,  36 
Honey-bee,  206 
Hoplocarida,  165 


Horseshoe  crab,  189 
Hydra,  41,  43 
Hydractinia,  41,  53 
Hydrocorallina,  41,  54 
Hydroides,  90,  108 
Hydrozoa,  41,  43 
Hymenoptera,  167 
Hypermastigida,  17 
Hypotrichida,  19 


Idothea,  166 
Inarticulata,  86 
Inermia,  90 
Infusoria,  18,  25 
Insecta,  200 
Isokontae,  21 
Isopoda,  166 


Joenia,  17 
Julus,  167,  199 


Keratosa,  36 


Lacrymaria,  18 
Lamellibranchiata,  122,  124 
Larvacea,  232 
Lecythium,  18 
Leech,  115 
Lepas,  165,  188 
Lepidonotus  (Polynoe),  96 
Lepidoptera,  167 
Lepralia,  86,  88 
Leptoclinum,  232 
Leptolinae,  41 
Leptomedusae,  41 
Leptoplana,  66 
Leptostraca,  165 
Lernaea,  165 
Leucosolenia,  36,  40 
Lichnophora,  29 


INDEX 


273 


Limax,  123 
Limnaea,  123 
Limulus,  166,  189 
Lingula,  86 
Lionotus,  18 
Lithobius,  166,  199 
Lobata,  63 
Lobster,  167 
Loligo,  123,  153 
Long  clam,  138 
Lophomonas,  17 
Loxosoma,  86 
Lucernaria,  42,  59 
Lug- worm,  102 
Lumbricus,  90,  109 
Lyssacina,  36 


Macracanthorhynchus,  79 
Macrobdella,  91,  115 
Madreporaria,  42,  61 
Malacostraca,  165 
Mastigamoeba,  17 
Meandrina,  42,  61 
Meckelia,  77 
Melampus,  143 
Melicerta,  84 
Membranipora,  86,  88 
Metamastigota,  17 
Metoncholaimus,  81 
Metridium,  42,  59 
Michtheimysis,  182 
Microciona,  40 
Microsporidia,  20 
Microstomum,  66 
Millepora,  41,  54 
Mnemiopsis,  63 
Modiolus,  122,  134 
Molgula,  232,  234 
Mollusca,  122 
Molluscoida,  86 
Monas,  17 
Monaxonida,  36 
Monocystis,  19 
18 


Monogenetica,  66 
Monozoa,  66 
Mosquito,  208 
Mounting,  248 
Multicilia,  17 
Mussel,  134 
Mya,  122,  138 
Mycetozoa,  18 
Myriapoda,  166,  199 
Mytilus,  122,  124,  134 
Myxidium,  20 
Myxospongida,  36 
Myxosporidia,  20 
Myzostoma,  90 
Myzostomida,  90 


Narcomedusae,  41 
Narcotizing,  245 
Nassula,  18 
Nautilus,  124,  164 
Nebalia,  165 
Nemathelminthes,  79 
Nematoda,  79 
Nemertinea,  66,  77 
Neocrinoidea,  212 
Neomenia,  123 
Nereis,  90,  91 
Neuroptera,  167 
Noctiluca,  21,  35 
Nosema,  20 
Notostraca,  165 
Nuclearia,  18 
Nucula,  122 


Obelia,  41,  45 
Octopoda,  124 
Octopus,  124,  164 
Oikopleura,  232 
Oligochaeta,  90 
Oligotrichida,  19 
Oniscus,  184 
Onychophora,  166 


274 


INDEX 


Opalina,  18 
Ophiura,  211,  219 
Ophiurida,  211 
Ophiuroidea,  211,  219 
Opisthobranchia,  123 
Orbicella,  42,  61 
Orthoptera,  167 
Oscarella,  36 
Ostracoda,  165 
Ostrea,  122,  137 
Oxytricha,  19,  29 
Oyster,  137 


Pagurus,  166,  179 
Pallene,  166 
Pantopoda,  166 
Paramecium,  18,  25 
Parasabella,  107 
(Parypha)  Tubularia,  41,  51 
Patella,  123 
Pauropoda,  167 
Pauropus,  167 
Pecten,  122,  136 
Pectinaria,  90,  101 
Pectinatella,  86,  88 
Pectinibranchia,  123 
Pedata,  212 
Pedicellina,  86 
Pedipalpida,  166 
Pelecypoda,  122,  124 
Pennaria,  41 
Pennatula,  42 
Pennatulacea,  42 
Pentacrinus,  212 
Peranema,  17 
Pericolpa,  42 
Peripatus,  166 
Peritricha,  19 
Peromedusae,  42 
Perophora,  232,  238 
Petasus,  41 
Phacus,  33 
Phalangida,  166 


Phalangium,  166 
Phanerozonia,  211 
Phascolosoma,  90,  119 
Phoronidea,  231 
Phoronis,  231 
Phoxichilidium,  166,  198 
Phrynus,  166 
Phylactolaemata,  86 
Physalia,  41,  54 
Phytomastigophora,  21 
Phytomonadida,  21 
Placophora,  122 
Planaria,  66,  67 
Planocera,  66,  70 
Plasmodium,  20 
Platyhelminthes,  66 
Pleurobrachia,  63 
Pleurotricha,  29 
Plumatella,  86,  88 
Pneumoneces,  71 
Podophrya,  19 
Polychaeta,  90 
Polychoerus,  66 
Polyclad,  70 
Polycladida,  66 
Polygordius,  90 
Polymastigida,  17 
Polynoe,  90,  96 
Polystomum,  66 
Polyzoa  (Cestoda),  66 

(Molluscoida),  86 
Porcellio,  184 
Porifera,  36 
Preparations,  245 
Proteomyxa,  18 
Protobranchia,  122 
Protochordata,  231 
Protomastigota,  17 
Protomonadida,  17 
Protophyta,  21 
Protozoa,  17 

Pseudoamellibranchia,  122 
Pseudoscorpionida,  166 
Pterobranchia,  231 


INDEX 


275 


Pulmonata,  123 
Pycnogonida,  166,  198 
Pyrsonympha,  17 


Quahog,  124 


Radiolaria,  18 
Razor-shell  clam,  140 
Regularia,  211 
Renilla,  42,  61 
Rhabdocoelida,  66 
Rhabdopleura,  231 
Rhizopoda,  18 
Rhynchobdellida,  91 
Rotifer,  84 
Rotifera,  84 
Round- web  spider,  196 


Sabella,  90 
Saccocirrus,  90 
Sagartia,  42 
Sagitta,  79 
Salpa,  232,  242 
Sand  mole,  180 
Sarcocystis,  20 
Sarcodina,  17,  22 
Sarcoptes,  166 
Scallop,  136 
Scaphopoda,  123 
Schizogregarinida,  19 
Schizoporella,  86,  88 
Scolopendrell#,  166 
Scorpion,  195 
Scorpionida,  166 
Scyphozoa,  41,  55 
Sea-anemone,  59 
Sea  cucumber,  226 
Sea  pork,  240 
Sea  urchin,  220 
Sections,  248 


Sepia,  123 

Septibranchia,  122 

Serpent-star,  219 

Sertularia,  41,  48 

Shrimp  (fairy),  185 
(goat),  184 

Silenia,  122 

Simocephalus,  165 

Siphonophora,  41,  54 

Solemya,  138 

Solpugida,  166 

Sow-bug,  184 

Spatangoidea,  211 

Sphaeractinomyxon,  20 

Spider,  196 

Spirochona,  19 

Spirorbis,  90,  109 

Spirostomum,  19,  27 

Spirotricha,  19 

Spirula,  123 

Spongilla,  36,  40 

Sporozoa,  19,  31 

Squid,  153 

Staining,  246 

Starfish,  212 

Stauromedusae,  42 

Stemonitis,  18 

Stentor,  19 

Stomatopoda,  165 

Streptoneura,  123 

Streblomastix,  17 

Strongylocentrotus,  211,  220,  221 

Styela,  232 

Stylaster,  54 

Stylochus,  66 

Stylonychia,  19,  29 

Suberites,  36 

Suctoria,  19 

Sycon,  36,  37 

Sycotypus,  143 

Symphyla,  166 

Synaptula,  212 

Syncoelidium,  66,  68 

Syzygies,  32 


276 


INDEX 


Taenia,  66 
Talorchestia,  166,  182 
Telosporidia,  19 
Tentaculifera,  19 
Terebratulina,  86,  89 
Tessera,  42 
Tetrabranchiata,  124 
Tetrastemma,  66,  77 
Tetraxonida,  36 
Thalassicolla,  18 
Thaliacea,  232 
Thousand-legs,  199 
Thyone,  212,  226 
Thysanura,  167 
Tima,  41 

Trachelomonas,  33 
Trachydermon,  122 
Trachylinae,  41 
Trachymedusae,  41 
Trematoda,  66,  70 
Trichinella,  79,  80 
Trichomonas,  17 
Trichonympha,  17 
Tricladida,  66 
Trochelminthes,  84 
Trypanosoma,  17 
Tubifex,  90 
Tubipora,  42 


Tubularia,  41,  51 
Tunicate,  232 
Turbellaria,  66,  67 


Uca,  166 
Unio,  122,  125 
Urochorda,  231,  234 

Venus,  124 
Vertebrata,  232 
Volvox,  33 
Vorticella,  19,  28 


Washing,  246 
Water-flea,  186 


Xiphosura,  166 


Yoldia,  122,  133 


ZOANTHARIA,  42 

Zoomastigophora,  17 
Zoothamnium,  19