652 CEREBRAL COMMISSURES OF THE MAMMALIA, 



fibres of the fornix are the first to develop,* so that in the early 

 Eutherian brain there is a stage which closely resembles the 

 adult condition in Metatheria with " anterior " and hippocampal 

 commissures and a complete absence of corpus callosum proper. 

 Combined with this absence of the corpus callosum there is a 

 persistence of the Bogenfurche, which completes the picture of 

 the Marsupial brain, constituting a veritable " Metatherian sta(je" 

 in the development of the Eutherian brain. These interesting 

 facts in the development of the higher mammalian brain, which 

 the recent work of Marchand and Martin have elucidated, fully 

 bear out the statement of the late Sir Richard Owen that the 

 hippocampal commissure^ in the Marsupials " represents the first 

 stage of the corpus callosum as it appears in the development of 

 the placental mammal " — a statement which has been repeatedly 

 misunderstood by Owen's critics. The work of Owen, which was 

 perfoniied almost fifty years ago with the crude methods of investi- 

 gation of that time, will stand the test of the latest methods of 

 investigation which the last few^ years have yielded. In the light 

 of our advanced knowledge of to-day, with all the delicate and 

 selective staining agents and improved methods of i-esearch, the 

 results of his labours on the brain of the nonplacental mammal 

 stand out as a lasting memorial to his close observation and 

 insight. The opposition which has been brought to bear against 

 his investigations by so many prominent biologists, some of whom, 

 from a less clear comprehension of the subject, attempt to 

 depreciate the value and question the accuracy of his work, can 

 hatve no other result than to expose their own ignorance. Even 

 as late as last year, an English writer well known in neui'ological 

 literature, in a disparaging attempt to find fault with Owen's 

 work on Platypus, simply laid himself open to the accusations 

 with which he ineffectually attempted to stamp the work of the 

 great 8ava7iL The result of the present research on the cerebrum 

 of a large series of Monotremes and Marsupials, with the methods 

 of Golgi and Weigert, is to completed vindicate Owen from the 



* Martin, loc. cit. 



