THE CHROMOSOMES OF THE COMMON HOUSE 

 MOSQUITO, CULEX PIPIENS L. 



P. W. WHITING 



Zoological Laboratory of the University of Pennsylvania 1 



SEVEN TEXT FIGURES AXD SEVEN PLATES 



CONTENTS 



1. Introduction 524 



11. Observations 525 



A. Spermatogenesis 525 



a. Introductory 525 



b. Spermatogonia 525 



c. First spermatocyte 530 



d. Second spermatocyte 537 



e. Spermatids 538 



f. Pathological cells 538 



B. Ovarian mitoses 539 



C. Mitoses of the thoracic hypodermis .541 



D. Summary of observations 541 



III. Discussion 542 



A. Introductory 542 



B. Technique 543 



a. Experiments and observations 543 



b. Review and criticisms 546 



C. Synizesis 547 



D. Continuity of the chromosomes 548 



E. Chromosome number 549 



F. Nucleoli, heterochromosomes. and cytoplasmic bodies 550 



G. Metaphase, stages a and b 552 



H. Pseudosynapsis, synapsis, and heredity 554 



IV. Literature cited 561 



1 Contribution from the Zoological Laboratory of the L T niversity of Penn- 

 svlvania. 



523 



