HISTORY OF THE PROCEPHALIC LOBES OF EPEIRA 



CINEREA. 



A Study in x\kachnid Embryology. 



AVERY E. LAMBERT. 



TABLE OF CONTENTS. 



PAGE 



I. Historical Statement 413 



II. Materials and Methods 419 



III. Origin of the Germ Layers, and Formation of the Cephalic Plate 422 



Part 1. Formation of the Blastoderm 422 



Part 2. Formation of tlie Blastodisc 423 



Part 3. Formation of the Primary Thickening, or Primitive 



Cumulus 425 



Part 4. Formation of the Secondary, or Caudal, Thickening 425 



Part 5. The Ventral Plate 428 



IV. Development of the Procephalic Lobes. Stages 1-11 429 



V. Formation of the Adult Brain 445 



VI. The Eyes of Epeira J^" 



VII. Comparison of the Araneid Brain with that of other Arthropods 452 



VIII. General Considerations 454 



Acknowledgments 455 



Bibliography 455 



Plates 461 



I. HiSTOTjicAL Statement. 



Amoii^' the ol>jecls to attract tlic attention of the earliest workers 

 in the field of invertebrate embryology, the stndy of the Arachnids 

 occupied an interesting and important place. 



The results of work done on the Araneina, however, have been very 

 general in their character ; few investigators have undertaken special 

 problems relating to the subject. Within a few years several excel- 



Thb Jouknal of MoRrHOLOGY. — Vol. XX, No. 3. 



