DEDIFFERENTIATION IN PEROPHORA 667 
healed, and the piece was irregularly lobed, as if swollen 
out from two or more centres. It would appear that there was 
an actual accumulation of fluid in the interior, as in the spheres 
produced by sponge choanocytes (Huxley, 1921a). Usually the 
test-cells were nearly absent in some regions, rather densely 
ageregated in others. No regeneration, however, took place, 
and death occurred quicker in the peptone than in the sea- 
water. Death took place in one to three days in peptone, 
two to four in water. An interesting point was that, before 
death, many of the test-cells always left the matrix of the 
test. and crawled out on to the bottom of the dish. They still 
preserved their characteristic shapes at first, but eventually 
all rounded off preparatory to dying. 
(b) Botryllus.—This genus is unsuitable for experiment 
owing to the small size of its zooids and their intimate connexion. 
One system, however, was seen in which all the zooids had 
become reduced te shapeless but healthy-looking lumps ; 
the test round them had degenerated save for a thin layer. 
Some form of dedifferentiation had cbviously occurred. 
8. Discussion. 
Perophora happens to be an organism in which dedifferentia- 
tion and resorption affect the whole individual in a very striking 
way. In higher forms, thanks to their self-regulating 
mechanisms, their size, the bulk of their skeletons, and other 
factors, the processes do not affect the individual as a whole. 
None the less, similar processes play a large part in many 
phenomena, both normal and abnormal, throughout the animal 
kingdom. 
Tn the first place it is important to realize that the ‘ struggle 
of the parts’, to which Roux (1881) first drew attention, is 
a very real struggle ; that the organism is in one aspect simply 
an equilibriam between a number of parts, some in a relation 
of simple competition, some in a relation of control of or 
subordination to others; and that the relative success or 
failure of any one part, the degree to which it is developed, 
depend or have depended upon its success in this struggle. 
