ON PHOItONIS OVA US, STRE THILL WRIGHT. 
147 
Fig. 21. — Through the commencement of the metasome. The 
afferent blood-vessel (a. v.) is visible ; n. r., the part of the nerve-ring 
on the oral side. Slide A 1 . 
Fig. 22. — A more proximal section. Both limbs of the alimentary 
canal are supported by the median mesentery ( mes .). Both longitudinal 
blood-vessels (a.v., e.v.) are visible. Slide A 1 . 
Fig. 23. — A more proximal section. The longitudinal muscles (l. m.) 
form strong bundles. Slide A 1 . 
Fig. 24. — Showing part of the invagination (inv.) at the proximal 
end of the muscular part of the body. Slide A 2 . 
Fig. 25. — Through the distal part of the non-muscular region of the 
body. Slide A 2 . 
Fig. 26. — From another series of “ transverse ” sections, through 
the region close to the base of the lophophore ; n. r., part of the 
nerve-ring; neph., nepliridia. (Zeiss C Obj.) Slide B 1 . 
Fig. 27. — A small regenerating fragment which is not yet provided 
with an orifice to its tube. Slide M. 
Fig. 28. — Regeneration practically complete, the distal end of the 
tube having been formed as a lateral oiitgrowth developed on the 
proximal side of the septum (s.). Slide Q. 
PLATE 9. 
Fig. 29. — A regenerating specimen which is commencing to divide. 
At the distal end, the muscular part (muse.) is developing, while the 
lophophore ( l .) is recognisable owing to the presence of a septum 
dividing its body-cavity from that of the metasome; /., zone of 
transverse fission, accompanied by the formation of a tube-septum. 
The adipose tissue (ad.) is present in large quantity. The proximal 
end is lobed, indicating a previous fission, further evidence of which is 
afforded by the tube-septum (s.). Slide L. 
Fig. 30. — A larger specimen in the same condition. Slide O. 
Fig. 31. — The first indication of fission is afforded by the formation 
of the annular tube-septum (s 1 .), which in this case occurs at the 
commencement of the non-muscular part of the body. Slide Q. 
Fig. 32. — A later stage in the fission-process. The two products 
of fission are completely separated, the distal one showing a lobed 
proximal end, and the proximal one showing signs of regeneration 
distally. Slide N. 
Fig. 33. — The proximal member of the result of the occurrence of 
fission, the evidence of which is the tube-septum ( s .) and the lateral 
outgrowth of the tube (t.) on its proximal side. Slide Q. 
VOL. 62, PART 2. NEW SERIES. 
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