ON RHORONIS OVALIS, STRETHIIjL WRIGHT. 
131 
shallow invagination ( inv .) above described. PL 8, fig. 25, 
represents a section passing through the non-muscular part 
of the body, and shows the thin character of the body-wall 
in this region. 
PI. 8, fig. 26, is from another series of sections, and it 
represents a section through the distal end of the body, not 
far from the lophopliore. A considerable part of the nerve- 
ring [n. r.) is visible, as well as both nephridia ( neph .). The 
small lobes projecting into the body-cavity, near the tubes of 
the nephridia, are probably parts of the funnels of these 
•organs. 
Regeneration and Fission. 
In the material under consideration there is no need to 
make a careful search for evidence of regeneration. It is 
more difficult to find a lophopliore provided with tentacles of 
the full length than to find one with immature tentacles. 
It is, moreover, a striking and most obvious fact that the 
dimensions of the individuals vary to such an extent as to be 
unintelligible on any hypothesis of orderly growth from the 
immature to the mature condition. It may further be noted 
that there is no relation between the condition of the lopho- 
phore and the size of the specimen. It will be convenient to 
analyse the facts under the following heads : 
(a) Regeneration of the lophophore. 
(b) Direct evidence of transverse fission. 
(c) Method by which the tube of the proximal segment is 
-completed. 
(d) Size of regenerating individuals as indirect evidence of 
fission. 
(e) Position of die zones of fission. 
(a) Regeneration of the Lophophore. 
Assuming provisionally that transverse fission is a process 
of normal occurrence, it is obvious that the conditions under 
which a new lophophore is formed is not quite the same in 
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