822 
DE. J. S. BOWEEBANK ON THE ANATOMY 
Explanation of the Plates. 
PLATE XXYII. 
Fig. 1. Fibro-meiribranous tissue in which the layers of fibre cross each other at various 
acute angles, from Polymastia robusta, Bowerbank, MS., X 308 linear: page 
751. 
Fig. 2. Fibro-membranous tissue in which the layers of fibre cross each other at about 
right angles, from Polymastia robusta, Bowerbank, MS., x666 linear: page 
751. 
Fig. 3. Fibro-membranous tissue from the dermal membrane of a species of Stematu- 
menia. The fibres are disposed without order, xl83 linear: page 761. 
Fig. 4. Fibro-membranous tissue containing a single layer of parallel fibres on a portion 
of the membrane from an excurrent canal of one of the common honeycomb 
sponges of commerce, x666 linear: page 751. 
Fig. 5. A portion of the dermal membrane of a young 8tematumenia, with cells which 
r produce the primitive fibres dispersed on its inner surface : — «, «, cells in situ, 
T, which have each produced a fibre, X 666 linear : page 752. 
Fig. 6. Three fibres in progressive states of development exhibiting no indications 
of an ultimate separation from the basal cell ; b, showing the mature termina- 
tion of the fibre previous to separation ; c, exhibiting the collapsed remains 
of the exhausted basal cell, x 666 linear : page 752. 
Fig. 7. Solid keratose fibre from a cup-shaped specimen of the best Turkey sponge 
of commerce in the condition in which it came from the sea, Xl75 linear: 
page 754. 
Fig. 8. Fibres of the skeleton of Halichondria oculata, Johnston, illustrating spiculated 
keratose fibre, Xl75 linear: page 755. 
Fig. 9. A young fibre of Halichondria Montagui, Johnston: a, the apical spiculum, 
X 175 : page 755. 
Fig. 10. A fibre from the skeleton of Halichondria cegagropila, Johnston, illustrating 
the structure of multispiculated keratose fibre, xl08 : page 755. 
Fig. 11. A longitudinal section of a small fibre of the skeleton of Raphyrus Griffitlisii, 
Bowerbank, ms., showing the irregular disposition of the spicula within it, 
X90 linear: a, one of the spicula, Xl75 linear: page 755. 
Fig. 12. Simple keratose fistulose fibre from Spongia Jistularis, Lamarck, X 108 linear : 
page 756. 
Fig. 13. Compound fistulose keratose fibre from the skeleton of an AulisMa, X 100 
linear: a, a, the minute tubular fibres traversing the central ca\ity of the 
skeleton-fibre: page 756. 
Fig. 14. A portion of one of the skeleton-fibres of AulisMa, exhibiting the secondary 
canals radiating from the primary ones, x300 linear: page 756. 
