STRUCTURE AND DEVELOPMENT OP REISSNEr’s FIBRE, 113 
Fig. 4. — Esox lucius. X 28. 
Fig. 5. — Rana temporaria. X 128. 
Fig. 6. — Splienodon (Hatteria) pnnctatus. X 24. 
Fig. 7. — Gallus domesticiis (19-day chick), x 24. 
Fig. 8. — Microtus arvensis. X 52. 
Fig. 9. — Lepus cuniculiis. x 24. 
PLATE 2. 
Fig. 10. — Petromyzon fluviatilis. Part of a transverse section 
through the hinder part of the mid-hrain, showing the paired condition 
of the isthmic canal. X 320. 
Fig. II. — P. flnviatilis. Part of a horizontal section through the 
same region of the brain, showing the junction of the right and left 
factors of Reissner's fibre at a point just anterior to the isthmic canal 
(here median and not visibly a paired structure). X 340. 
Fig. 12. — P. fluviatilis. Part of a median sagittal section through 
the end of the spinal cord showing the canalis centralis expanding 
into a sinus terminalis, within which is seen a tangled mass of 
Reissner's fibre, lying against the meningeal wall. X 250. 
Fig. 13. — P. fluviatilis. A similar section (but slightly oblique) 
through the sinus terminalis of another specimen. Reissner’s fibi'e 
is inserted into the meningeal sheath of the sinus. X 250. 
Fig. 14. — Ichthyomyzon (Entosphenus) tridentatus. A 
sagittal section through the tail of an aminoccete of 105 mm. showing 
the sinus terminalis and Reissner’s fibre. X 80. 
Fig. 15. — 1. tridentatus. Part of a sagittal section through the 
tail of an ammoccete of 90 mm. showing a considerable tangle of 
Reissner’s fibre almost filling the sinus terminalis. X 350. 
Fig. 16. — Petromyzon fluviatilis. Part of a sagittal section 
through the spinal cord showing the interrupted coiling of Reissner’s 
fibre. X 600. 
Fig. 17. — Myxine glutinosa. — Sagittal section through the sinus 
termina is, showing a large mass of coiled Reissner’s fibi-e. At the 
apex of the mass the fibre is more loosely looped, x 260. 
Fig. 18.— M. glutinosa. Another section from the same series as 
fig. 17, passing almost centrally through the mass of fibre. X 260. 
Fig. 19. — Geotria australis. Part of a median sagittal section 
through the posterior commissure, showing a tangle of Reissner’s fibre 
below the sub-commissural organ (from one of Prof. Dendy’s prepara- 
tions). X 310. 
VOL. 58, PART 1. NEW SERIES. 
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