636 CEREBRAL COMMISSURES OF THE MAMMALIA, 



valuable advice, I have examined a considerable num))er (about 

 thirty) brains of the Monotreme and Marsupial orders, more 

 especially those of Ornithorhynchns and Perameles nasuta. A 

 knowledge of the gross anatomy having been obtained by dissec- 

 tions of fresh brains, the minute anatomy was worked out in 

 serial sections of the whole brain cut in coronal, sagittal and 

 horizontal planes. The Weigert-Pal and Golgi staining methods 

 were used for most of the work, supplemented by occasional use 

 of anilin blue black. In addition to the above, the cerebrum has 

 been examined in the Phalanger, Macropus, Koala, Kangaroo-rat, 

 Dasyurus and Echidna, and compared with those of the rabbit, 

 pig, cat, dog, guinea-pig and mole. From a series of foetal 

 specimens of Phalangista of various ages, I was enabled to make 

 out many points in the cerebral development. Through the 

 kindness of Professor Wilson and Mr. J. P. Hill, I. was enabled 

 to examine some beautifully stained series of sections of foetal 

 Kangaroos and Bandicoots, as well as a very valuable series of 

 sections of a foetal Platypus, whose external appearance is described 

 in this number of the Society's Proceedings. For the abundant 

 supply of material with Avhich this research was conducted, I am 

 deeply indebted to Dr. C. J. Martin, Mr. J. P. Hill and Dr. 

 Meredith, of Raymond Terrace. To Mr. Robert Grant I am 

 under a deep obligation for much valuable assistance in the 

 histological work. 



In the Marsupial and Monotreme brain the greatest interest 

 centres in the unique arrangement of the cerebral commissures, 

 the uniformity of whose general plan throughout these orders 

 indicates the close relationship between the Proto- and Meta- 

 theria, and separates them as a distinct and well defined group 

 from all the Eutherian orders. 



This paper is merely intended as a synopsis of that part of the 

 subject which relates to the commissures. The complete results 

 of the work on the non-placental cerebrum I hope to pi*esent to 

 the Society in a short time. 



At an early stage in the development of the non-placental 

 mammal, the mesial wall of the j^rosencephalic vesicle becomes 



