AUTHOR'S ABSTRACT OF THIS PAPER ISSUED Reprinted from JOURNAL OP MORPHOLOGY 



BT THE BIBLIOGRAPHIC SERVICE, MARCH 28 Vol. 35, No. 2, June, 1921 



THE SPERMATOGENESIS OF LEPISMA DOMESTIC^ 



HARRY H. CHARLTON 



Osborn Zoological Laboratory, Yale University 



six PLATES (NINETY-FIVE FIGURES) 



CONTENTS 



Introduction 381 



Material and methods 382 



Observations 384 



External sexual characters 384 



Male reproductive system 384 



Spermatogonia 384 



The growth period 386 



The first spermatocyte 389 



Resting stage of the second spermatocyte 390 



The second maturation division 391 



The centrosome in the spermatogonial and maturation divisions 392 



The spermatid 393 



The spermatozoa 398 



Mitochondria 401 



Discussion 401 



Resting stage of the second spermatocyte. 401 



The idiochromosomes 402 



Synapsis and reduction 403 



The centrosome 404 



The acrosome 405 



The middle-piece 406 



Comparison with Orthoptera 406 



Summary 408 



Bibliography 409 



INTRODUCTION 



Cytologists have long found the class Insecta to be a very 

 fertile field for investigation, but the first order and, according 

 to many, the most primitive, namely, the Thysanura, seems to 

 have been neglected. According to Harvey ('16), only three 

 papers dealing in any way with the cytology of any closely 



381 



