STUDIES ON CHROMOSOMES 



VIII. OBSERVATIONS ON THE MATURATION-PHENOMENA IN CER- 

 TAIN HEMIPTERA AND OTrfER FORMS, WITH CONSIDERATIONS 

 ON SYNAPSIS AND REDUCTION 



EDMUND B. WILSON 



From the Department of Zoology, Columbia University 



NINE PLATES 



CONTENTS 



Introduction 346 



I. The maturation-divisions in Oncopeltus and Lygaeus with reference to 

 the sex-chromosomes 



1. The diploid chromosome-groups 350 



2. The first spermatocyte-division 351 



3. The interkinesis 354 



4. The second spermatocyte-division 355 



5. Size-relations of the sex-chromosomes in Oncopeltus 357 



II. The growth-period 



1. Outline of the stages 359 



2. Stages a to d. The pre-synaptic stages. Comparison with other 



insects 362 



3. Stage e. Synapsis, synizesis 376 



4. Stages / and gr. Post-synaptic spireme (pachytene, diplotene), and 



the diffuse or confused stage 377 



5. Stages h to j. The prophases 381 



6. Comparative cons' derations regarding the growth-period 387 



7. Comment on the sex-chromosomes in Oncopeltus 390 



III. Critical considerations on the maturation-phenomena based on a compari- 

 son of the Hemiptera with Tomopteris, Batracoseps and other 

 forms 



1. The question of synapsis 391 



2. The question of the reduction-division 407 



3. The chromosomes and hereditv 419 



345 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 13, NO. 3 

 OCTOBER, 1912 



