VARIATIONS IN THE DEVELOPMENT OF 
TIMOLUOS, POLVFIEMG Ss 
WILLIAM PATTEN, Ph.D. 
PROFESSOR OF ZOOLOGY IN DarTMOUTH COLLEGE, Hanover, N.H. 
CONTENTS. 
Pace 
PINE @ VU CTI OIN a. 5-isciiensocsensnnsnsnceotene gue ctaetarne eo aeeattee ye Seae ey Saneren ett eemeeneteme 21 
ELROD SK Of TAA. ACHEIT, | SELLILL ILE NCCC mera eee ea 23 
WVELHOMS Of AOU LAI EIS: NIGEL LL ame eat ae ee ee 2 
COS ESTO PMV GT LALEOT ATE LILLE RTLLL noe arene ena eae 28 
DESCRIPTION OF THE DIFFERENT CLASSES OF VARIATION — METHOD 
OF CLASSIFICATION. 
Lee LIN VAG EN-ACIO IN| (OF ZAYP IPE NID IAG ES 32.2 ecco, tenses tesa nace cee eee ee ee 30 
Hivasination not due toexternal stress: co. 22-ccec.cec.ceseeneierasee teense eee 31 
Bearing on lung-books of arachnids, and visceral cleffs of vertebrates.. 32 
TT PABSENCE OF APPENDAGES..i:...c:.tccccescedae afl ets ec bat ros aes se eee 33 
The three anterior pairs of thoracic, and the abdominal appendages, 
ALE eMOS tatne qimeM tly, ASE mit essence cece eee eee nee eee 34 
A. Absence of Abdominal Appendages VELY COMMOMN........-.0.--v0eeeeeveee- 34 
The Telopore: relations to primitive streak, anus, apex of body, 
and apical growth: comparison with vertebrates ..........0...20.0.....--..- 35 
D SER 10) Bd BS) Ko) oY see eae eR Ee renee 36 
Baw Asymmetry of Abdominal APPCHAGLES..--cncccr nce sercea na ravaertcecee see eeyeeee aes 36 
GaerAbsenceof LkOr Acie APPCHAGRES 0.0.0 ceccxsectnssasetecaeesseseestrne eee 36 
Mimetor appearance of same in mormall eg psec steers eee 36 
Observations on disappearance of same in “ving abnormal eggs........ 37 
al Seyi wp Wu Si. 2.222 seaecenteneeéeneskctcensscccberesnusete tac houees usec soahe eee eee een 37 
Progressive reduction of thoracic appendages from before back- 
WAN GS ieee ofc iencsecebansecees sccece onsnsnscsusn Giasenscadisctotcuseeuass@iec bette cetera as gee Be cena 37 
Greatemvitality of last) three panes cou cs.3.s0.2<cazce acyconrnantiapeaeeeee erereeeoeee 38 
Symmetrical and asymmetrical reduction of same ...........-.--..---...------- 38 
III. MULTIPLICATION OF APPENDAGES AND OTHER ORGANG..............-...-. 39 
Multiplication of chelicerae and corresponding sense-organs (lateral 
GYES)y ANG! DEUTOMELES...-...2:.s.-c3 ayant. tvacesagertoesae eeeeeeee tee ee ee ee aac 40 
IV. Fusion oF RIGHT AND LEFT HALVES OF THE EMBRYO AND AN- 
MERO-ROSTERIOR: DEGENERATION -icsssscac-ore-e-c-eemercs reese eeteeeenseesee eecencee 40 
Method of growth and arrangement of Aa/fmetameres...............-.-.----- 41 
Fusion and degeneration of segmental organs is in reverse order of 
Gein FOTIM AON +..<:..--222-650.ceseecdecrcunaweneeae ne wc eaceee tere ieee cere pence ete scans 4I 
