of the Central Nervous System in Ascidia d:c. 225 



wliich originate from the " fibrillar net ; " in the next place 

 he has found two types of nerve-cells (such as Gerlach had 

 previously supposed to occur in the spinal cord of the Verte- 

 brata*), namely a type which sends its nervous process 

 directly to a peripheral nerve, and a second type, the nervous 

 processes or, at any rate, '' processes " of which divide up in 

 the fibrillar net f. The ramifications of this latter kind of 

 processes, however, in Haller's opinion, form an actual reti- 

 cular net ; therefore they anastomose and form real meshes, 

 which, as already pointed out, is in opposition to my concep- 

 tion of them. Then Dr. Haller, like Gerlach, thinks that the 

 fibrillar net (or web, as I believe) is also formed by " non- 

 nervous processes " of the ganglion-cells, and therefore by 

 Deiter's " protoplasmatic processes," which, according to what 

 has been above stated, is not in agreement with the results at 

 wdiich I have hitherto arrived. Dr. tialler did not know 

 Prof. Golgi's very important investigations ; according to 

 these it seems to me to be made out that, at any rate in the 

 higher Vertebrata, the fibrillar web is formed by the nervous 

 processes, of which there are never more than one to each cell, 

 and not hi/ the protoplasmatic processes, which do not serve to 

 connect the different ganglion-cells, but, in accordance with 

 Golgi's opinion, exclusively have to do with the nutrition of 

 the cells. Anastomoses or unions between the different 

 ganglion-cells by their processes, which Haller describes as 

 the regular condition in the Rhipidoglossa, I have been unable 

 to demonstrate with certainty in the groups of animals inves- 

 tigated by me, at any rate as the rule. As regards the nume- 

 rous nuclear processes described by him, I have been unable, 

 as already stated, to convince myself positively of their exist- 

 ence from my preparations, although in many cases it has 

 seemed to me probable. 



These are the most important points in which, from a 

 rapid perusal of Dr. Haller's important memoir, I do not think 

 that 1 can agree with him ; on the whole, however, his and 

 my results may be said to confirm each other to a very con- 

 siderable extent, and possibly we have thus advanced to a 

 somewhat more solid basis for investigations upon this diffi- 

 cult subject. In a letter Dr. Haller has moreover informed 

 me that he has met with the conditions described by him not 

 only in the MoUusca, but also in the Chastopoda \ and in the 



* J. Gerlach, " Von deru Riiclieiimark," in Strickker's ' Hanclbuch der 

 Lelire von den Geweben ' (Leipzig, 1872), p. 684. 



t This kind of cells, however, Gerlach called '' cells without nervous 

 processes," therefore only with protoplasmatic processes. 



X I have also, both in Polychreta and Oligochseta, met with conditions 

 corresponding to those which I have described in the Myzostomes. 



