210 Mr. F. Nansen on the Histological Structure 



preliminary report upon some of the results at which I have 

 arrived in the course of the investigations which I undertook 

 last summer (June and July 1885) in Alverstrommen (near 

 Bergen) , at the expense of Joachim Friele's legacy, which by 

 the liberality of the Direction of the Museum was granted to 

 G. A. Hansen and myself. I will expressly call attention to 

 the fact that these investigations are not completed, and that 

 therefore, for the present, it will not be advisable to go more 

 in detail into the subject ; but as I believe that some of these 

 results may be of general interest, I venture in the meanwhile 

 to publish them in their imperfect form. 



The results at which I arrived in my investigations upon the 

 histological structure of the nervous system of theMyzostomata, 

 and which Ihave described in my memoir upon the structure of 

 this group of animals *, stood in so remarkable a manner in 

 agreement with many of the characters which Prof. C. Golgi 

 (of Pavia) has described in the central nervous system (brain 

 and spinal cord) of man, that it became a matter of much interest 

 to me to have investigated some groups of animals lying be- 

 tween these widely separated forms. With this object in view 

 I turned to the group of Ascidia (so much a subject of dispute 

 from a systematic point of view), with the nervous system of 

 which I had previously occupied myself, and in which I ex- 

 pected to be able to find something of interest. In the next 

 place I wished to examine some low vertebrate animal, and 

 selected the hag-fish {Myxine glutinosa), of which I could 

 obtain abundant material. 



The points which it was of essential interest to have inves- 

 tigated were as follows : — 



1. Does the fibrillar mass of the central nervous system 

 consist of two constituents + — a, a fibrillar net, or, as I will 

 call it for the sake of clearness^ a fibrillar tvebj consisting 

 of fine fibrilhe, which in their crooked and intricate course 

 cross one another in every direction ; and i, couvscy percurrent 

 " nerve-cylinders^^'' which either traverse tlie whole fibrillar 

 mass of the central nervous system, and thus connect its 

 different parts with each other, or run out into peripheral 

 nerves ? 



2. Have all the nerve-cells (whether unipolar or multi- 

 polar) only one real nervous process ('' prolongation nerveux 

 ou fonctionnel"), and can the nerve-cells be divided into the 

 following two types : — a, first type, of which the nervous pro- 



* " Bidrag til Myzostomernes Anatomi og Histologi," Bergeus Mu- 

 seum, 1886. 



t As described in tlie above-cited work on Myzostoma, p. 3o. 



