THE
EVOLUTION THEORY

VOLUME II

THE
EVOLUTION THEORY

BY

Dr. AUGUST WEISMANN

PROFESSOR OF ZOOLOGY IN THE UNIVERSITY OF FREIBURG IN BREISGAU

TRANSLATED WITH THE AUTHOR'S CO-OPERATION

BY

J. ARTHUR THOMSON

REGIUS PROFESSOR OF NATURAL HISTORY IN THE UNIVERSITY OF ABERDEEN

AND

MARGARET R. THOMSON

ILLUSTRATED

IN TWO VOLUMES

VOL. II

LONDON
EDWARD ARNOLD

41 & 43 MADDOX STREET, BOND STREET, W.

1904

All rights reserved

CONTENTS

LECTUREPAGE
XX.Regeneration[1]
XXI.Regeneration (continued)[23]
XXII.Share of the Parents in the Building up of the Offspring[37]
XXIII.Examination of the Hypothesis of the Transmissibility
of Functional Modifications		[62]
XXIV.Objections to the Thesis that Functional Modifications
are not transmitted		[80]
XXV.Germinal Selection[113]
XXVI.Germinal Selection (continued)[136]
XXVII.The Biogenetic Law[159]
XXVIII.The General Significance of Amphimixis[192]
XXIX.The General Significance of Amphimixis (continued)[210]
XXX.In-breeding, Parthenogenesis, Asexual Reproduction,
and their Consequences		[238]
XXXI.The Influences of Environment[265]
XXXII.Influence of Isolation on the Formation of Species[280]
XXXIII.Origin of the Specific Type[299]
XXXIV.Origin of the Specific Type (continued)[330]
XXXV.The Origin and the Extinction of Species[346]
XXXVI.Spontaneous Generation and Evolution: Conclusion[364]
INDEX[397]

LIST OF ILLUSTRATIONS

FIGUREPAGE
35 B (repeated).Hydra viridis, the Green Freshwater Polyp.[4]
96.A Planarian cut transversely into nine pieces[6]
97.A Planarian which has been divided into two by a longitudinal cut[14]
98.The leg of a Crab, adapted for self-mutilation or autotomy[17]
99.Regeneration of the lens in a Newt's eye[21]
100.Regeneration of Planarians[25]
101.A Starfish arm[27]
76 (repeated).Diagram of the maturation divisions of the ovum[39]
82 (repeated).Fertilization in the Lily[59]
91 (repeated).Hind-leg of a Grasshopper[83]
102.Brush and comb on the leg of a Bee[84]
103.Claw on the leg of a 'Beach-fly'[85]
104.Digging leg of the Mole-cricket[86]
105.Ovary of a fertile Queen-Ant and ovaries of a Worker[91]
106.Three Workers of the same species of Indian Ant[97]
107.A, B. Larva of a Caddis-fly[105]
107 C.Leptocephalus stage of an American Eel[133]
108.Nauplius larva of one of the lower Crustaceans[161]
109 A, B.Metamorphosis of one of the higher Crustacea, a Shrimp[162]
109 C.Second Zoæa stage[163]
109 D, E.Mysis-stage and fully-formed Shrimp[164]
70 (repeated).Daphnella[166]
110.The largest of the Daphnids (Leptodora hyalina), with summer ova
beneath the shell		[166]
111.Nauplius larva from the winter egg of Leptodora hyalina[167]
112.Development of the parasitic Crustacean Sacculina carcini[168], [242]
113.The two sexes of the parasitic Crustacean Chondracanthus gibbosus[170]
114.Zoæa-larva of a Crab[171]
115.Caterpillar of the Humming-bird Hawk-moth Macroglossa stellatarum[178]
3 (repeated).Full-grown caterpillar of the Eyed Hawk-moth[178]
4 (repeated).Full-grown caterpillar of the Eyed Hawk-moth[179]
8 (repeated).Caterpillars of the Buckthorn Hawk-moth[179]
116.Development of the eye-spots in the caterpillar of the Elephant
Hawk-moth Chærocampa elpenor		[180]
117.Caterpillar of the Bed-straw Hawk-moth Deilephila galii[181]
118.Two stages in the life-history of the Spurge Hawk-moth Deilephila euphorbiæ[182]
119.Caterpillar of the Poplar Hawk-moth Smerinthus populi[184]
120.A, Symmetrical, and B, asymmetrical curve of frequency[207]
121.Life-cycle of Coccidium lithobii[214]
122.Conjugation of a Coccidium (Adelea ovata)[216]
123.Conjugation of Coccidium proprium[218]
79 (repeated).The two maturation divisions of the 'drone eggs'[236]
124.Alternation of generations in a Gall-wasp[245]
125.The two kinds of galls formed by the species[246]
126.Ovipositor and ovum of the two generations of the same species
of Gall-wasp		[247]
127.Life-cycle of the Vine-pest (Phylloxera vastatrix[249]
128.Heterostylism[254]
38 (repeated).A fragment of a Lichen[261]
129.Aberration of Arctia caja, produced by low temperature[276]
130.Skeleton of a Greenland Whale, with the contour of the body[313]
131.Peridineæ: species of Ceratium[325]