Fig. 1. M. graffi. Fig. 1—17. (Scibcrl lioin. im. '/ir,- Zeiss Oc. 4. Cam.-luc. 15onix-carminc, Picric acid.) Section of the 

 upper extremity of a ri'cei ver-sliaped organ (from a transverse section), h. Internal prominence of the concentric 

 layers. »./., n.f ., n.f". IJumlles of fibrils communicating with the organ. Some fibrils of «/'. are seen penetrating 

 to its inner contents, c. Mesial duct of the [irolongation. /■., h. Nuclei. v. \'acuolus. a. Cell, communicating, 

 probably, with the organ. 



■i 2 — 6. (Seibert .horn. im. '/le- Zeiss Oc. i. Cam.-luc. Horax-carniiiu-, Picric-acid.) Portions of transverse sections through 

 the bulb of the receiver-shaped organs. 



» 2. A. and B. Two successive sections through the bulb of a receiver-shaped organ. /'. Prominence ot the concentric 

 layers. v., v., v". Vacuoli surrounding the organ; nuclei are seen in some of them Iv'.). a., b.. c. Bundles of 

 fibrils, d. Point where the fibrils traverse each other. 

 ^. Section through the upper extremit}' of the bulb of a receiver-shaped organ, in which a nucleus (a.) is situated. 

 ('. X'acuolus. b. Point where fibrils traverse each other. 



» 4. Shows the communication between the bulb, and two large bundles ((/. and b.) of fibrils which penetr.ite the mem- 



brane of the bulb, c, d. Vacuoli containing nuclei. 

 5. A. and B. Two successive sections, a. Nucleus in a constricted cavity communicating with the bulb. c. A 

 nucleus, d. A cell, probably, communicating with the organ, v. v. Vacuoli in connection with which nucleoli are seen. 



» 6. Section, passing, laterally, through a bulb, showing its intimate communication with bundles (6., c, d.) of fibrils, a. 

 Centre of the bulb. The membrane of the upper extremit}- of the bulb is not seen in the section. Ic. Cell com- 

 municating with the bulb. 



» 7. (Zeiss F. Oc. 2. Cam.-luc. Osmic acid, Hæmatoxylin.) From a horizontal section which has passed, transversall)", 

 through the bulb of a receiver-shapeci organ whose contents are seen to be darkly stained by the reagents. 

 a. and 6. Bundles of fibrils communicating with the bulb. 7i. Nucleus. 



i 8. (Seibert horn. im. '/,6. Zeiss Oc. i. Cam.-luc, Hæmatoxylin.) Longitudinal section of a part of the prolongation 

 of a reciever-shaped organ. (The same as in fig. 10.) 



:> 9. (Zeiss F. Oc. i. Cam.-luc. Hæmatoxylin.) Portion of a transverse section, showing the termination of the prolonga- 

 tion [xu.) of a receiver-shaped organ, a. and b. Bundles of fibrils issuing from the parapodial ganglion. 



» 10. (Zeiss CC. Oc. 3. Cam.-luc. Hæmatoxj-lin.) Portion of a transverse section passing through a parapodial ganglia. 

 X. Bulb of receiver-shaped organ, with its coagulated contents. ch. Point where fibrils traverse each other, n. c. 

 Ganglionic cell. a. Parapodium. 

 II. [Seibert hom. im. '/le- Zeiss Oc. 2. Cam. luc, Picro-carmine.) Section of a giant-cell of a parapodial ganglion, 

 containing- almost separated, nuclei, in one of which a corpuscle (a second nucleolus) is situated beside the 

 nucleolus. The latter nucleus is less staining. 



» 12. (Zeiss F. Oc. 2. Cam.-luc. Picro-carmine.) Nucleus of a giant-cell. 



13. (Zeiss F. C)c. 4. Cam.-luc. Saffranine.) Nucleus of a giant-cell, in which the chromatic reticulation is distinctlig 

 seen. In the nucleus several granules and refracting vacuoli are seen. 



14. (Zeiss F. Oc. i. Cam.-luc. Picro-carmine.) Nucleus of a giant-cell, and cellular contour. A vacuolus is, distincl}-, 

 visible in the nucleolus, and, in connection with the latter, dark staining ribs are seen in the chromatic structure of 

 the nucleus; producing, thus, a kind of less staining vacuoli (vide also fig. 12). 



;- 15. (Zeiss F. Oc. i. Cam.-luc. Picro-carmine.) Nucleus of a giant-cell containing 2 nucleoli, and the cellular contour. 

 » 16. (Zeiss CC. Oc. i. Cam.-luc. Hæmatoxylin.) Lateral section of a giant-cell; the protoplasm shrunk to a central 



mass, and showing the converging of the fibrils towards the roots of the two prolongations. 

 » 17. (Zeiss CC. Oc. i. Cam.-luc.) A hook-apparatus of M. graffi, isolated with solution of caustic potash. 

 » 18. 31. carpenteri. Graff. (Zeiss CC. Oc. i. Cam.-luc.) A hook-apparatus; drawn from a transverse section. 

 » ig. M. giganteum, >t. sp. (Zeiss hom. im. '/is- Oc. Cam.-luc. Osmic acid. Hæmatoxylin.) Transverse section of a 



supporting rod, showing the hexagonal structure of the central fibrillar mass. a. Outer, more homogeneous, yellow layer. 

 ■■■' 20. M. graffi, n. sp. (Arbitrarih' magnified.''. Reserve hooks, with part {a.) of the chief hook, showing their fibrillar 



structure, and the prominent fibrosity of the base. 



21. Portion of a hook, still more magnified than in fig. 20, and showing the somewhat twisted fibrillity. 



22. M. carpenteri. Graff. Dwarf-male. (Zeiss F. Oc. 1. Cam.-luc. Borax-carmine, Picric acid.) Portion of a trans- 

 verse section, showing the upper extremity of a supporting rod [s.li.) with its muscles (m., m ., »«".), and two uni- 

 polar cells (a., 6.) which cend their prolongations towards the extremit}' of the rod. &. Cell containing 2 nuclei. 



23. M. graffi, n. sp. (Seibert hom. im. '/s- C)c. I. Cam.-luc. Borax-carmine, Picric acid.) Portion of a transverse 

 section, showing the structure of the glandular mass (a.) surrounding the posterior stomach and the anterior cloacal 

 canal, me. Epithelium of the stomach. ovd. Dorsal oviduct. b. Globule of the glandular mass, containing a 

 nucleus and several of the minute corpuscles, resembling small nuclei, distributed in the mass. 



» 24. M. graffi, n. sp. (Zeiss CC. Oc. 4. Cam.-luc.) Portion of a horizontal section, showing the opening {p.) of a 

 latero-ventral oviduct into the cloacal canal. The aperture is seen situated in a papilla {p.). a. Ciliated epithelium of 

 the oviduct; the cilia are seen to be directed inwards, c. Epithelium of the cloacal canal at the aperture, i., d. Epi- 

 thelium of the cloacal canal. 



» 25. 71/. graffi, n. sp. (Zeiss F. Oc. 2. Cam.-luc. Hæmatox_\iin.) The ciliated epithelial cells of a latero-dorsal oviduct, 

 and some of the mucous globules occurring in these oviducts. 



» 26. M. graffi, n. sp. (Zeiss CC. Oc. 4. Cam. luc.) Section of a latero-ventral oviduct. 



:> 27. 31. carpenteri Graff. (Zeiss F. Oc. i. Borax-carmine. Picric acid.) Portion of a transverse section, showing the 

 ciliated epithelium of the dorsal side of the body-cavity, in its central part (anterior part of the uterus) ov. Ova. 

 em., Im. The two layers of dermal muscles. 



» 28. M. gignntenm, n. sp. (Seibert hom. im. '/s- Oc. i. Borax-carmine, Picric acid.) Portion of a transverse section, 

 showing the structure of the glandular mass of the hook-apparatus. The fig. shows the point where the inner 

 branch unites with the branch of the hooks (vide PL II, fig. i h.Jc). a. Elongate glandular cells, containing fibrous 

 protoplasm, b. Long cylindrical cells, c. Globular cells with prolongations and small deeply-staining nuclei, d. A 

 fibrillar fibre communicating with the cells. /. Deeph'-staining deposits, g. Canal, in the glandular mass, communi- 

 cating with the canal of the chief hook. 



