Literary Notices. xix 



Fatigue causes the nuclei of the cell capsule to decrease in size. 

 Rest, if sufficiently long, will restore the normal morphological pecu- 

 liarities of cells that have been fatigued by electrical stimulation. 

 The process of recovery is slow, twenty-four hours being required to 

 repair the damage done by five hours stimulation. 



The curve of nerve rest or fatigue is not a straight line. 



The author appends a long list of bibliography. 



[ c. H. T.] 



The Brain of Mud Fishes.' 



The Dipnoi are full of interest to the morphologist and have al- 

 ready attracted their share of attention. Owen and Weidersheim 

 have described the anatomy of Ceratodus and Giinther and Huxley 

 have investigated Lepidosiren. The habit of some of these fishes of 

 encasing themselves in a firm casket of mud and mucous during the 

 dry season has enabled naturalists to bring them alive from their na- 

 tive waters. Dr. Burckhardt was fortunate enough to receive a num- 

 ber of such cases through the agency of Herr W. Jezler, a mer- 

 chant who lived at Bathurst, Senegambia, but who died while search- 

 ing for the early stages. 



It thus became possible to make a careful study with the aid of 

 modern technique, for which Dr. Burckhardt was well equipped by 

 his extended experience. Some of the results of these studies were 

 published in this Journal for September, 1892. 



The prosencephalon is relatively much larger than in Petromy- 

 zon but is otherwise very similar. As in that genus there are well- 

 developed hippocampal lobes to which, as the writer has shown to be 

 the case in bony fishes, the lateral radix of the olfactory passes. The 

 diencephalon reminds one in many respects of the Lampreys, but in 

 others approaches Amphibia. The cerebellum is developed about as 

 in the latter group, while the elongated medulla and extensive meta- 

 plex gives the brain a very primitive aspect. 



The cord. The arrangement of the elements in the cord is very 

 simple. The spongioblastic framework is a mere radial system as in 

 the embryo and the gray matter is of small extent. 



The substantia gelatinosa appears for the first time in this group. 

 The cells of the ventral cornua are of relatively enormous size. The 

 Mauthner fibres are also of great size and exhibit a fibrous structure, 



1 Das Centralnervensystem von Protopterus annectens. Eine vergleichend- 

 anatomische Studie. Dr. Rudolf Burckhardt. R. Friedlandcr and Son, 

 Berlin, 1892. 



