Fig. I, 2. M. gigantcum, n. sp.. (Zeiss CC. Oc. i. C;im.-luc. Osniic acid. Hæmato.xylin.) Two succe.sive horizontal .sections 

 through the ventral nerve-cord. Fig. i is a more ventral section than fig. 2. In fig. i.the section slopes so much that the 

 anterior i)art is e.xcluded. in. Intermediate nerve, n.st^. — n.sf'. The five ])airs of large nerves, w'. — w". The si.\ pairs of 

 fine nerves. oc.m. The oesophageal commissures. t.cm. Large tiansverse commissures, cm. Fine transverse commissures 

 which are, however, not usually, seen in their whole extent, cm . The pair of laige ganglionic cells is, here, seen in 

 connection with the commissure. 



> 3. M. graffi, n. sp. (Zeiss CC. Oc. i. Bora.x-carmine. Picric acid.) Ideal horizontal section of the ventral nerve -cord, con- 



structed from a series of sections. The litera-significations are the same as in figs, i and 2. tc. A third desciiption of fine 

 transverse commissures, found, solely, in this sj^ecies, probably pertaining, originally, to the large transverse com- 

 missures (tern.). 



» 4 — y. M. cirrifcnini, F. S. L (Zeiss CC. Oc. 2. Cam.-luc Osmic acid. Bora.x-carmine.) Four succesi\e horizontal sections 

 through the ventral nerve-cord. Of these, fig. 4 is the most ventral, and fig. 7 the most dorsal. The litera-significations 

 are the same as in the preceding figures. In fig. 1, most of the intermediate nerve {Ln.) is seen; the section slopes so 

 much anteriorly, and ventrally, that in the opposite end some transverse commissures become visible, a. Ganglionic cells. In 

 fig. ') a part of the intermediate nerve {i.n.) is still visible, tcm. Posterior large transverse commissure, seen to commimicate 

 with lateral groups of ganglionic cells. Fig. 6. a. The anterior segment from which the oesophageal commissures (ocm.) 

 and the first pair of fine nerves issue. In fig. 7, m. Many dorsally situated ganglionic cells are transsected. o.c.m. Oesop- 

 hageal commissures, transsected in their recurved course. 



» 8. 31. (jigantcum, n. sp. (Zeis CC. Oc. 4. Cam.-luc. Bora.x-carmine. Picric acid.) Transverse section through the anterior 



extremity of the ventral nerve-cord. n.sV. ist pair of large nerves, on whose e.xterior side the 2nd pair of fine nerves occur. 

 h. and c. Points where the prolongations from groups of cells converge and pass into the nerves. n. Root of the ist 

 pair of fine nerves, d. Groups of cells situated between these nerves and the roots of the commissures. /. Groups of cells 

 whose ])rolongations converge, forming a chiasma (a) with the ])rolongations of the op]josite groujj. p. Cuticular septa 

 originating in the membrane of the outer neurilemma-sheath. 



» 9. M. gigunfeum, n. sp. Dwarf-male. (Zeiss CC. Oc. 4. Cam.-luc. Borax-carmine. Picric acid.) Transverse section of 



the mesial ventral cord. On the one side, the section has passed through the root of a large nerve, whilst, on the oppos- 

 ite side, it has passed between two nerves. One of the large transverse commissures is seen in the middle, only partially 

 affected by the section, a. The point, in the commissure, v.^here the prolongations of the mesial groups of cells (wc.) of 

 both, ventral and dorsal, sides converge, and traverse each other. On the ventral side, the groups of cells are seen situated, 

 one on each side of the intermediate nerve (in.). h.h. Points, at the extremites of the transverse commissure, where pro- 

 longations from groups of cells converge, and pass into the longitudinal commissures, c.c. Latero-dorsal groups of cells, 

 whose prolongations communicate with the transveise commissure, d. d. Large cells, whose prolongations enter the longitud- 

 inal commissure on the ventral side. c. Grouj) of cells situated under the root of the large nerve (one cell only is seen 

 in this section). /. Group af cells, v.hich send their ]irolongations direcdy into the large nerve (vide also fig. 16 b.). 



» 10. M. graffi, n. sp. (From jjhoto. taken with a Seibert hom. im. '/s- Borax-carmine. Picric acid.) Transverse section of 

 the ventral ner\e-cord and circumjacent .jiarts. n.sk. Membrane of the outer neurilemma-sheath; its structure is not uni- 

 form ; neither in consistency nor staining. The inner neurilemma-sheath is well developed, and consists of several layers. 

 in. Intermediate nerve. ch. Point where the prolongations of two large cells traverse each other. nc. Latero-dorsal gang- 

 lionic cells. cli . Branch of the intermediate nerve. m'. Muscles, m. m" . Ventral muscles, e. Ventral ectoderm. in. e. 

 Ectoderm of the stomach. 



» II. M. giganteum, n. sp. Dwari-male. (Zeiss F. Oc. 2. Cam.-luc. Bora.x-carmine. Picric acid.) Mesial portion of a trans- 

 verse section through the ventral nerve-cord, shov/ing a pair ot the large dorsal ganglionic cells whose prolongations form 

 a chiasma (ch.) and penetrate into the longitudinal commissures on each side (vide also fig. 2 cm', fig. 14 and PI. IX, fig. 5, 6'.). 

 in. Intermediate nerve, nc. Ganglionic cells. /,■. Connective-tissue nuclei. k'. Less-staining connective-tissue nuclei (rV 

 me. Epithelium of the stomach. 



" 12. M. giganteum, n. sp. (Zeiss F. Oc. 2. Cam.-luc. Borax-carmine. Picric acid.) Mesial part ot transverse section through 

 the ventral nerve-cord, n.s.k. Homogeneous membrane of the outer neurilemma-sheath, from which septa (/.) proceed into 

 the ventral cord, and separate the groups of cells, v.hilst, a fev,- sejata i)ass to the membrane of the intermediate nerve (/«.), 

 which gives off a branch that passes into the longitudinal commissure at h. ; the fibrils of this branch are seen to issue, one, 

 from each of the few nervous tubes of the intermediate nerve, nc, nc. Two ganglionic cells whose prolongations traverse 

 each other; vacuoli are seen in their [jrotoplasm, (^probably artificially produced). mc-". Cell situated on the outer side 

 of nc, and which has its prolongations directed towards the converging point of the prolongations of nc, nc, nc'., nr'"., 

 nc*. Ganglionic cells v.'hose prolongation are, also, directed towards the same jjoint. nc'-. Large cell corresponding to d 

 in fig. 9 and to PI. IX, fig. be a. Point at the e.xtremity of a large transverse commissure which, in the section, is only 

 parriy seen, and where ganglionic cells, that correspond tn /; fig. (), converge. r. The opposite extremity of the transverse 

 commissure entering into the longitudinal commissure. Some ganglionic cells are, also, seen here. d. Dorsal, coarse 

 longitudinal nervous tubes of the longitudinal commissure. 



» 13. M. giganteum. n. sp. (Zeiss, F. Oc. 2. Cam.-luc. Osmic acid, Hæmatoxylin.l Portion of a horizontal section through 

 the ventral part of the ventral nerve-cord, showing a ])roblematir multipolar cell (^a.) c/jntaining 2 nuclei; one of its pro- 

 longations (b.) is seen to divide and, T think, become loosed out. 



» 14. M. gigantenm, n. sp. (Zeis F. Oc. 2. Cam.-luc. Osmic acid, Hæmatoxylin.) Portion of horizontal section, showing the 

 »chiasma« formed by the prolongations of the dorsal pair of large ganglionic cells, (vide also fig. 2 cm'.). 



» 15. M. cirrif'erum, F. S. L. (Seibert horn. im. '/,,;. Zeiss Oc. i. Cam.-luc. Osmic acid. Borax-carmine.) Portion of a 

 horizontal section through the ventral nerve-cord, showing the connection between the dorso-lateral ganglionic cells (nc.) 

 (coriesponding to c fig. 9), and the large transverse commissure situated between the 2nd and 3rd i)air af large nerves. 

 Mc. Large pair of ganglionic cells. /,'. Connective-tissue nuclei. One of the fine transverse commissures is, also, partly seen. 



» 16. M giganteum, n. sp. (Zeiss, F. Oc. i. Cam.-luc. Borax-carmine, Picric acid.) Portion of a transverse section, through 

 the ventral nerve-cord at the root of a large ner\e, where a dorsal grouj) (6.) of ganglionic cells is seen that send their pro- 

 longations, direct, into the nerve, g. Septa of the ner\e. c. Dorsal part of the fibrillar mass passing into the nerve, and 

 isolated by a septum, d. Group of a few ganglionic cells situated under the root of the nerve (vide also PI. IX, fig. 6, a and 

 fig. 4 & 5, r ■''.). f. Connective-tissue membrane, a. Gioup of ganglionic cells ya. and I), corresjiond to c. and f. in fig. 9). 

 n.sh. Outer neurilemma-sheath. 



