A STUDY OF THE MALE GERM CELLS IN NOTONECTA 



ETHEL NICHOLSON BROWNE 



From the Zoological Laboratory, Columbia University 



TEN PLATES 



CONTENTS 



I. Introduction 62 



II. Material and technique 63 



III. Chromosomes 64 



A. Observations 64 



1. Notonecta undulata 65 



2. N. irrorata 66 



3. N. insulata 67 



4. N. glauca (Pantel and Si:n6ty) 69 



B. Discussion 70 



1. Relation between chromosome number and species 70 



2. Temporary fusion and separation of chromosomes 75 



3. The XF-pair 77 



IV. Karyosphere 78 



A. N. insulata 78 



1. Early growth stages and formation of karyosphere 78 



2. Description of karyosphere 81 



3. Dissolution of karyosphere 82 



B. N. undulata 82 



1. Early growth stages and formation of karyosphere 82 



2. Description and dissolution of karyosphere 83 



C. N. irrorata 84 



D. Conclusions and comparisons 84 



V. Prophases 86 



A. General description 86 



1. N. insulata 86 



2. N. irrorata 86 



3. N. undulata 87 



B. Detailed description 87 



1. N. insulata . 87 



a. Ring 87 



b. Cross 89 



c. Double rod 90 



d. XF-pair 90 



2. N. irrorata 91 



3. N. undulata 91 



C. Discussion 91 



61 



