REPRODUCTION AND PARASITISM IN THE 
UNIONID.E 
GEORGE LEFEVRE and WINTERTON C. CURTIS 
Professors of Zoology in the University of Missouri 
THIRTY-NINE FIGURES 
FIVE PLATES 
CONTENTS 
Introduction 79 
The marsupium 81 
Breeding seasons 87 
Conglutination of embryos 90 
Histological structure of the marsupium 92 
Stratification of unfertilized eggs 93 
Structure of the glochidium 94 
Behavior and reactions of glochidia 98 
Reactions of hooklcss glochidia 100 
Reactions of hooked glochidia 101 
The parasitism 103 
Infections with hooked glochidia 104 
Infections with hookless glochidia 107 
Susceptibility of fishes to infection 109 
Duration of parasitism Ill 
Histological changes in cyst-formation Ill 
Liberation from the cyst and post-larval stages 114 
INTRODUCTION 
The threatened extinction in the Mississippi River and its 
more important tributaries of those species of the Unionidae 
whose shells have been taken in enormous numbers during the 
past fifteen years for manufacture of pearl buttons has led the 
United States Bureau of Fisheries to undertake an extensive 
investigation to determine the possibility of artificial propagation 
of the commercial species, and to devise such means as may be 
practicable of restocking depleted waters which present favorable 
conditions for their growth. The general direction of the investi- 
gations has been placed in the hands of the writers, who for the 
past three years have devoted as much time as their other duties 
