DEDIFFERENTIATION IN PEROPHORA 647 
was very similar to that presented by an early stage of dedif- 
ferentiation. After this, however, a brownish colour appeared 
in the animals, and this heralded true degenerative changes 
leading to death. Adult individuals are often found in nature 
in a similar state, and these, too, always appear to die without 
full dedifferentiation ; in fact it would appear that natural 
death occurs in Perophora through this means, the conditions 
in old zooids being such that they cannot maintain themselves 
in full tone, and thus undergo incipient dedifferentiation, 
which, in these old zooids, is not able to complete itself, and 
so leads on to degeneration and death. Similar failure of old 
individuals to adjust themselves to changed conditions is of 
course well known in the case of regeneration ; a discussion 
of the whole subject will be found in Child’s book, ‘ Senescence 
and Rejuvenescence ’ (19154). 
When smaller zooids were taken, however, quite different 
results were obtained. 
(b) Simple Dedifferentiation (Clavellina type). 
If the stolon be cut very close to the zooid on either side, 
the zooid will usually dedifferentiate as in Clavellina. That is 
to say, the siphons contract, the zooid shrinks, becomes 
increasingly opaque, and eventually draws right away from the 
tunic. The final stages of this process were represented by 
opaque spheroidal masses with a diameter of one-third to one- 
half that of the original zooid, and often with no or extremely 
slight trace of siphons. The heart usually continued to beat 
even in this condition. Examples are shown in fig. 1. Here 
the shortness of the stolon is noticeable. 
In most examples of this process the stolon was either very 
short, or underwent dedifferentiation concomitantly with the 
zooid, or both. In all such cases the system, with its relatively 
small proportion of stclon, was similar to a stolon-zooid 
system in Clavellina, and behaved in an essentially similar 
way. 
In one point there was a difference. I never observed such 
complete reduction in Perophora as in Clavellina. Further, 
[ was not able to obtain redifferentiation by replacing the 
