of the Central Nervous System in Ascidia etc. 223 



The Brain in Myxine I have as yet investigated only 

 quite superficially, and therefore I will not at present enter 

 upon any particular description of it. This much, however, 

 may be said — the size of the nerve-cells appears to vary still 

 more than in the spinal cord. There are very large cells 

 which occur only in small numbers, and at the same time 

 there are extremely small cells, which appear in very consider- 

 able numbers, especially in the anterior parts of the brain ; in 

 the cerebrum they are diffused quite uniformly throughout 

 the whole mass. The large cells generally stain more strongly 

 than the smaller ones ; but this can be of no significance from 

 a physiological point of view, as among both the larger and 

 the smaller cells there seem to be cells of both the types 

 described by Golgi, namely with processes which go directly 

 to form peripheral " nerve-fibrillaj/' and with processes which 

 divide up in the fibrillar web, as is not difiicult to demon- 

 strate. In many preparations I believe quite definitely that I 

 can see anastomoses between the protoplasmatic processes of 

 different large nerve-cells ; in spite of the most careful exam- 

 ination with homogeneous immersion-lenses (Zeiss yV) I was 

 unable to come to any other conclusion than that such anasto- 

 moses were present ; nevertheless I will say nothing decided 

 upon this point, and will still treat it as doubtful, until it is 

 possible to make a more thorough examination of many 

 preparations. 



Conclusion. 



If, after giving this certainly very superficial description 

 of investigations upon the central nervous system in the 

 Ascidia and Myxine^ we bring together in conclusion the 

 results which may be regarded as arrived at, and compare 

 them with the seven different questions or propositions which 

 we commenced by formulating, it must certainly be admitted 

 that, omitting the last question, which has not been particu- 

 larly treated of here, the others appear to have been pretty 

 thoroughly confirmed, and the conditions found are in agree- 

 ment both with what I have previously found in the Myzo- 

 stomes and with what Prof. Golgi has ascertained in man and 

 in the higher Vertebrata (Mammalia) ; it might therefore 

 from this even now appear to be a probable supposition that 

 these conditions occur throughout tlie whole animal kingdom, 

 in which generally a more developed nervous system exists. 



In passing I will call attention to an agreement between 

 the above description of the spinal cord of Myxine and the 



