of the Central Nervous System in Ascidia &c. 215 



the fibrillar web. Hitherto I have been unable to find any 

 constant difference in this respect between cells of different 

 sizes. 



Besides these cells in the peripheral layer surrounding the 

 central fibrillar mass there is also another form of ganglion- 

 cell, which occurs in the fibrillar mass itself. These are small 

 multipolar cells with an ovate nucleus. Van Beneden and 

 Julin have observed these cell-nuclei in sections ; they have 

 also stated that they were possibly of nervous nature, saying * : 

 " II s'agit probablement la de petites cellules nerveuses allon- 

 gdes dans le sens antero-post^rieur, unipolaires ou bipolaires, 

 et dissdmin^es dans la substance fibrillaire." I have ex- 

 amined these cells both in sections and by the aid of macera- 

 tion ; the latter method especially gave me the best results ; 

 and I find that there can be no doubt as to their truly nervous 

 nature. They are small multipolar cells, generally at least 

 tripolar, the form of which reminds us in no small degree of 

 the three-cornered form of small cells in the brain of the 

 Vertebrata ; the processes which originate from their most 

 pointed end are the nervous processes, and these I have 

 often been able to trace very far, in macerated preparations 

 I have even succeeded in isolating them for a long distance ; 

 but I have nowhere found any ramification. In sections I 

 have often seen them directed towards the origin of the peri- 

 pheral nerves ; and I therefore regard it as in the highest 

 degree probable that these small tripolar or multipolar cells 

 belong, at all events for the most part, to the type of nerve- 

 cells, the nervous prolongations of which go directly to form 

 peripheral nerve-cylinders. In the other processes of these 

 cells, which may therefore be said to coiTCspond to " Deiler's 

 protoplasma-processes," I have frequently been able to see 

 ramifications. 



In conclusion, with regard to this question of the form and 

 the processes of the nerve-cells I will remark that it has 

 appeared to me on two occasions that I could see true pro- 

 cesses from cell-nuclei, prolongations which united them- 

 selves again with other smaller cells. This therefore 

 would be something comparable with what Dr. Bela Haller 

 has described in the Rhipidoglossa, in which he thinks he has 

 found numerous nuclear processes of the most different forms. 

 Of the actual nuclear nature of these processes, however, I 

 feel by no means perfectly convinced ; I am afraid that 

 the images of such a nature which I have hitherto had before 

 me in the Ascidia may be due to an optical illusion, and 



* Loc. cit. p. 334. 



