300 JULIAN S. HUXLEY 
in the zooids (results in course of publication). The further 
progress of events in these organisms, however, is determined 
by the emergence of the cells from the tissue into the blood, 
leading to the resorption of the zooid. Here, in these spherules, 
the cells emerge from the tissues, but must remain in position, 
since there is no means by which they can migrate elsewhere. 
Sheht mercury poisoning also causes emergence of some of the 
endoderm cells from the gut of late Echinoid plutei. It 
is probable that total or partial resolution of the tissues into 
separate cells is a general occurrence in dedifferentiation, 
but that it is masked in many cases, e. g. m Clavellina, A study 
of these phenomena, together with that of dissociation of cells 
as observed in particular chemical solutions, as, e. g., observed 
by Gray (5), will throw light on the problem of cell-coherence 
in general. 
(4) The production of a definite dermal epithelium late in 
the history of many subdivided spheres is to be considered in 
relation to the observed fact that restitution-bodies with 
dermal epithelium are more viable than those composed of 
choanocytes alone (Huxley, 8). 
(5) The transition from a state in which no cell-outlines are 
visible (figs. 2, a; 6) to one where the cells are distinct (fig. 2, b) 
or separated (fig. 5) is to be compared with the formation of 
syncytia im Coelenterate restitution masses, as noted by 
Wilson and by de Morgan and Drew, and thei subsequent 
resolution ito cells. Here again a very important general 
phenomenon is made accessible to study. 
4. Dermat Biow-outs. 
In my previous paper three types of restitution were 
described, leading to: (1) normal regenerates, consisting of 
dermal and gastral cells in normal proportion. ‘hese formed 
spicules, and those that lived long enough produced normal 
miniature sponges. (2) Collar-cell spheres: small hollow 
spheres, consisting of a single layer of choanocytes, with no, or 
very few, other cells. (3) Collar-cell blow-outs : masses con- 
sisting mainly of collar-cells, blown out im one or more regions 
