XII THE CHICAGO ACADEMY OF SCIENCES. 
TABLE OF CONTENTS. 
Page 
PREEACE iy ace coe are tin a alg careers bis aie) el eee eicistere« steie ete iuloparetel oteiti ale orace anal ate eto raetetenenaes V 
I. General Morphology of the Lymmnzas.% 02.05.0052 ccs case oso 0 eee 1 
Li. Aes Sled oat heen o syrre eistarsichetancicoseh einen heres Orcas Cree oreo al 
2 Extemal) Appearance .ole tiie: Anima len meee cicero ames 5 
3) (General) Internal Anatomy) 52) o0sceeccs a semen eee eee 6 
as! Whe aDigestive A raGt .:cmce coe Sous Melerae) ests sion eie ike Sane 7 
bi. “he. awe so See ck eta ods tices ERG eee CeCe eer 8 
é.. he cRaditlaw 7 aos tcc oe ciclo cole aoe ae he AO oe eee 9 
d. The Reproductive Systenie occ. outer oe a si inietos «1 10 
e. The Nervous Systema... cee ste yo has dee eee nee 13 
f., “he Respiratory iSystem) cs ncccecesese ee eee eeeee 16 
¢. ThesRenal ‘System ca cicid scissile oe aise eek ote eros 16 
h.ikhe Cixculatory Systean «1.1.0... 52 sees san ae sere akties eee 17 
{... PhesMusculareSyst enmnai's asrercees cereiene ake ore selteeneren ocean 17 
4, Bibliography of Works Consulted: o05 cece. nus one ace ae 18 
Ie  Beology of tthe Teyminzas ei... 2 mt a ois aia leneve rele eens ce ees in eee 19 
a, General Environmental "Conditions... 255.2... 52.0. scenes 19 
b. Variation of the Lymnzid Shell in Different Environments.. 29 
¢, ALOcOMOtHON. :05 3.5 eres ete re onl Sere aieaGls ie etaelet heehee eas 32 
Gliding Ss Ses <aiklonae oe Sema oi ha patina 2 eh eae ee 33 
Hiuinehinig os. 8 Faas Loe Sid tacts rates havent cep ee ae. 
Thread -Spinnine. ec ceteerers oa acorn oceans eae no (o.oo 33 
Mechanism’ of cocomotion\cssj.eceeceiemen ceo eee 34 
Rate; of Locomotion 21,5226 dia:.-vtincsveerinetel= +)-)leree ote eee 35 
dd... RRESpinatiOmis ois cations o-= Saree Sere ah ots aaoehaeexstule noc erat r ie eetee eee 35 
AME Sahl) 10 Te ce Ceara ECE tee minora dake oimbit'd 0.0.9 ¢ 39 
£.~ Albniormallitves: Gare accuera cyoveis sceus, cvord stoke, ste nner neeleroned rete ere eee 40 
o' YRAGaSitiSin- ao jolssepe etek sages sine oTe eit acealsveteieeay tenets roeer renee terete 41 
Hs = WEROOGY saiva'cpietscarerstolereitte eaStevaters std. aheteta teres teren one pereneret ete eae tere 42 
i; JHood? for Other AimtimiallS\o.coic:ci0e ime eee ence oer 44 
j. Reproduction and (Nidiftexion.< 5071 c....2.seend- 46 oeeee 45 
kk. Experiments. ous Gsgne cscheles « <'s 's suena eevee trois 47 
I. Length of Late oaks Seisas sic cc's: xis ont eer Mere elo eee noe 51 
m. Bibliography of Works Consulted... ...5..60.++<.5. 6 ee 51 
Tis WDistributtom. an “Spacema-cre citi teres cies etetelerale elekel le oteheteneietcle ttt et eter 52 
A. The Present Distribatien o.oo. osetia see se eee 52 
Highteen Zoological (Regios. 5 ..< 1. 3.58 56 
Table of Distribution of American Lymnzas................ 61 
B: The Glacial Period, 2. tsiiareas ec uerce oc. uo eee rie eee ereeeners 67 
Post-Glacial. Dispersal Ft nh eo Ga eee ne ee eee 69 
Tertiary Lakes of the Great Basing... ice ees = «5s ere eee 73 
