F. A. POTTS. 
42 ^ 
On tracing the tissues from the stock into tlie area of pro- 
liferation the following changes may be seen to take place : 
(1) The cuticle becomes very much reduced in thickness. 
(2) The ectoderm increases in places to nearly twice its 
original thickness by continued division of its cells. But 
along certain lines little nuclear division takes place and the 
thickness remains that of the ectoderm of the stock. In 
fact it may be said that within the area of proliferation there 
exist as many centres of proliferation as there are stolons to 
Text-fig. 2. 
(L 
✓ 
As in Text-fig. 1, but representing a median section. The nerve-cord 
is shown, stopping short of the proliferating cushion. The centre 
of the latter is seen to consist mainly of a ineshwork of fibres, 
lietween which have penetrated large leucocytes, n. c. Nerve-cord. 
al. c. Intestine, an. Anus. d. Dorsal extension of mesoldastic 
tissue. Other letters as in Text-fig. 1. X 70. 
be produced. But anteriorly fresh centres are being con- 
stantly formed from a proliferating lip. 
(3) The proliferating area is formed by the last two seg- 
ments of the stock. In the last segment of the stock the 
body-cavity is largely occupied by a proliferation of meso- 
blastic tissue (PI. 23 bis, fig. 11), which penetrates into and 
forms the basis of the cushion formed by the proliferation of 
the ectoderm. It consists of a meshwork of connective tissue. 
