88 QUARTERLY CHRONICLE. 



described as enclosed in a delicate covering of connective 

 tissue^ which in the fresh state is closely applied to the 

 surface of the granular cell-substance, but in chromic acid 

 preparations becomes separated from it by a clear space^ 

 which the author denominates the " area." 



2. The peripheral nerve-fibres consist of an " axis- 

 cylinder/^ enclosed in a medullary sheath, and surrounded 

 by a delicate neurilemma of connective tissue. The axis- 

 cylinder isj as before said, a direct continuation of the cell 

 substance, whilst the medullary sheath, which occupies the 

 space between the axis-cylinder and the neurilemma, appears 

 to commence abruptly at the nerve-cell, but to have no other 

 connection with it. The neurilemma is described as con- 

 tinuous with the connective-tissue sacculus in which the 

 nerve- cell is lodged. In the central organs the fibres consist 

 only of the '^ axis-filament," and the author has never been 

 able to trace any direct continuation of these fibres into the 

 sheathed peripheral ones ; notwithstanding the frequent 

 assertion to the contrary of other observers. 



3. The matrix, as it may be termed, of the central nervous 

 masses presents different appearances in diff'erent parts. In 

 some places it exhibits more or less of a granular aspect, and 

 has been termed by the author the " granular matrix/' 

 whilst in others it has a finely reticulated structure, and has 

 thence been termed the '^ reticulated basis-substance." The 

 colour varies according to the greater or less prevalence of 

 the " axis-fibres," or of the '^ medullary fibres " by which it 

 is pervaded. 



As regards the blood-vessels, the author has nothing par- 

 ticular to remark. 



After these general histological observations, the remainder 

 of the paper is occupied with a full and minute description 

 of the structure of the spinal chord and brain, in which will 

 be found much highly interesting information. 



II. " The Histology of the Semicircular Canals and the 

 OtoUte-Sacculus of the Frog," by Dr. C. Hasse. 



In this paper we have a very minute and detailed account 

 of the structure of the parts in question, and a comparison 

 between it and that of the same tissues in the Mammalia 

 and birds. 



III. ''On the Egg of the Epherneridce,^' by Dr. H. Grenadier. 

 The author describes certain appearances observed by him 



in ova, procured from the larvce of a species of Ephemera. 

 The ova in question, about 0'27 mm. in length, by ()'12 mm. 

 breadth, were furnished at either end with a semicircular 

 appendage. These appendages were of a reddish-brown 



