'J'lic f/(i>ii/I/onlc cells arc. most Dl'tlicm, uniiiolai'. I ha\r oliserwtl, in tlu' mitral iirr\'ous sj'.stcm, oiil}' a few ccll^ orundoulit- 

 cdlv nuiltiiM)lar nature, anil the}' have been ronlined, pianeipall)-, tcj the i^osterior part of the cerebral gantjlia mentioned above. I con- 

 sider that, as a rule, each of the rranglionic cells — whether unipolar or multipolar — has onh- one real nerve-prolonrration. (_)f these 

 prolongations there are two types: one passing, directl)% into a periphi nc nerve to torni ,i nervous tube (tube nerveux; corresponding 

 to the : c}'linder-axis« of \ertebrates, and this ty])e is, I think, the most fre(|ui-nt one. The other ts'pe becomes loosened 

 out into the fibrillar reticulation of the central mass, out of which, again, nervous tubes spring. Regarding these two t}'pes, 

 vide PI. IX, fig. 3 —6. From the prolongations jjassing directl\- into the nerves, small branchlets issue, whose purpose is, I 

 think, to !>ring the prolongations into communicitKin with other parts of the nervous system. The cells of the \entral nerve- 

 coril var_\' \-ery much in size; their nuck-i var\-, liovvever, less than their protoplasm. I ha\-e, sometimes, obser\"ed nerve-cells 

 situated in the tibrillar mass of the longitudinal commissures; these cells have, however, been alwaj's small, vide pi. IX, fig. 4 

 and 6. Tlu- cells of the cerebral ganglia an- of more uniform size, and are smaller than those of the ventral cord. The 

 ganglionic cells are, as previously mentioned. pro\ided with connective-tissue membranes in v\'hich nuclei often occur. I h.ive 

 not observed any true cellular membrane belonging to the cells. The protoplasm of the ganglionic cells alwa)'s appears, in 

 sections, to ha\-e a distinct spongious aspect. The true structure of this protoplasm is difficult to determine; we find a 

 structural support extended (»spongioplasm! ), and this, I am inclined to regard, more, as isolating the hyaloplasm into 

 fibres, than Leydig appears to be. The spongioplasm extends, also, into the prolongations aiul there, I believe, parti}-, isolates 

 the h}-aloplasm into small tubes, or fibrils, and the prolongations accjuire, thus, their fibrillar appearance, and wliat appears, in 

 sections, as fibrils, is consequenth', the spongioplasm. Some of these slender tubes diverge, and form the branchlets issuing 

 from the prolongations; most of them, however, pass into the nerve, and form the nervous tube which springs from the cell. 

 In the cells of the second t}'pe, whose prolongations become lost in the fibrillar reticulation, the slender tubes diverge from 

 each other, and firm tlu' branchk-ts m which the prolongations terminate. 



In the peripheric, nerves, I have, often, obser\-ed ganglionic cells, more or ]es3, distant from the ventral cord; 

 they, howe\cr. occur in greatest number close to the origin of the nerves. In most of them. I ha\'e oliserved onl}- one pro- 

 longation, but, occasionally, I have, also observed two prolongations. In the ventral ner\'e-cord at the origin ot the large 

 nerves, I have, also, observed unipolar cells sending their prolongations, directh', into these nerves, without passing through 

 the fibrillar mass of the commissures. The seobservations are quite opposed to \'ignals negation of the existence of such cells, 

 situated in the ventral ganglia of Hirudo, as well as of ganglionic cells occurring in the peripheric nerves. 



Direct division of nuclei in the ganglionic cells. I have, several times, observed nuclei of the ganglionic 

 cells in a dividing state, vide PI. IX, fig, 8, and PI. \TI, fig. 11. I have never observed an}- trace of kan'okinese . and be- 

 lieve that, here, we have a direct division of nuclei. I have not, distinctl}', observed the division of the cells, but I have seen 

 indications of it, and I have, therefore, no doubt that this direct division of the nuclei is succeded b}' division of the cells. 

 I believe we ha\'e, here, thus, instances of direct division of cells in the nervous system. 



The fibrillar mass. The fibrillar appearance of the commissures, as well as that of peripheric nerves, is occasioned 

 by the spongioplasm which encloses, and isolates, the h}'aloplasm into tubes. I think, therefore — as Le}-dig states — 

 that the French designation tubes nerveusc" is a more correct one than die Fibrillen'- of the German scientists. 

 In the peripheric nerves, these tulles vary, considerabh', in diameter; some of them measure onl}- o.ooi — 0.002 mm. 

 whilst others measure up to 0.006 mm. in diameter. Most of these tubes spring, directl}-. from the ganglionic cells, as stated 

 above, but some of them, however, spring from the fibrillar central mass of the commissures, and these ones are, in my 

 opinion, the more slender tubes, especiall}'. As mentioned in connection with the description of the cells, the hyaloplasm of 

 the tubes is, by a structural support of spongioplasm, divided into several extremely slender tubes; this spongioplasm, and 

 these tubes are, however, in both, transversal and longitudinal sections, extremel}- difiicult to observe. I belie\-e it must be 

 this spongioplasm that has given rise to the Primitiv-fibrillen of Hermann. Whether the spongioplasm is, origina!l}% a part 

 of the nervous substance, or is derived, originall}', from the connective-tissue, I am unable to decide. It is, at all events, ad" 

 herent to the septa of the inner neurilemma-sheath, and it is scarcel}- possible to distinguish it from the smaller septa of the 

 sheath. In tr;uisversal sections of the nerves, granulations can, usu.ilh', be seen ; the granules are, however, not trans-sected 

 fibrils, but are tumefactions in the spongioplasm, produced b}" the union of several septa at these points. 



The ventral nerve-cord. The fibrillar mass of the longitudinal commissures is composed of ner\-ous-tubes, pass- 

 ing, transversall}', into the nerves, and, longitudinally, along the whole length of the commissures; and, also, of a fibrillar reticul- 

 ation extending throughout the commissures, but especiall}- situated in their centre. This filinllar reticulation is constructed, I 

 believe, parti}- of the fibrils or branchlets, issuing from the celi-prolongations passing directh- into the nerves, and parti}-, 

 from the cell-prolongations loosening themselves up into this reticulation, one of whose purposes is, I think, to promote com- 

 munication between the various tubes and the different parts of the nervous s}-stem. I am not disposed to assume that this 

 reticulation has such a spongious nature as Leydig supposes. I think that there are more-isokitetl fibrils, or slend(.'r tubes, 

 constructed in much the same wa}- as the tubes of the nerves, with a cord of h}-aloplasm enclosed in spongioplasm ; these 



