Some Notes on the Gametogenesis of 

 Ornithorhynchus Paradoxus. 



By 

 J. Bronte Gatenby, M.A., D.PMl. (Oxon.), D.Sc. (Lond.), 



Professor of Zoology and Comparative Anatomy, Dublin University. 

 (From the Department of Embryology, University College, London.) 



With Plates 12, 13, 14, and 1 Text-figure. 



Contents. 



PAGE 



1. Introduction ......... 475 



2. PREViotrs Work on Gametogenesis of Ornithorhynchus 



AND OF Echidna ........ 476 



3. General Note on the Structure op the Egg op the Sauro- 



psiDA .......... 478 



4. General Account of the Formation op Egg-membranes in 



Sauropsida and Mammalia ...... 480 



5. General Account of the Yolk Formation in Birds and 



Amphibia 482 



6. The Structure of the Ovary of Ornithorhynchus . . 483 



7. The Appearance of the Immature Ovary .... 484 



8. The Size op the Largest and Smallest Ovarian Oocytes . 485 



9. The Young Oocyte 486 



10. On the Early Establishment of a Polarity in the Oocyte 486 



11. Formation of Egg-membranes ...... 487 



12. Yolk Formation 489 



13. Formation of the Latebra ...... 490 



14. A Fully-formed Egg (diameter 4 mm.) .... 491 



15. Note On Spermatogenesis ...... 492 



16. Discussion 493 



17. Bibliography 494 



1. Introduction. 



In this paper I have described in as much detail as was 

 possible the oogenesis of the duck-billed platypus of Australia. 

 Owing to the unique position of the Prototheria, any new facts 



