306 JULIAN 8. HUXLEY 
mature larvae, these might adhere to and be actually embedded 
in the restitution-bodies (figs. 9, a; 10, a). In this situation 
their flagella would continue to beat. Transferring masses 
with embedded larvae by means of a pipette often resulted 
in detaching the larvae (fig. 10,b). Larvae that remained 
attached appeared to become resorbed into the masses, finally 
disappearing (fig. 9, a-c). Histological investigation of this 
has not yet been undertaken. 
7. ADHESION AND UNIFICATION OF RESTITUTION-BODIES. 
In section 4 an account has already been given of the fusion 
of a number of spheroidal bodies to form irregular masses, 
which later became spheroidal in their turn. These were all 
masses with excess of dermal cells. Some observations on 
masses with excess of choanocytes may also be given. Some 
four-day restitution-bodies were isolated in a hanging drop, 
The chief are shown in fig. 9, a. Most are covered with dermal 
cells, but two have dermal epithelium in part. Some have 
attached larvae. After two days these were seen to have 
fused (fig. 9, b). Three larvae and two other small restitution- 
bodies, not shown in fig. 9, a, had not shared in the fusion. 
On the next day the larvae were still visible, but the general 
form was not so irregular. The day after (fig. 9, c) the larvae 
were no longer visible, the blown-out region had increased, 
and the traces of the separate original masses have been 
almost lost, the mass looking quite unitary, though with 
slight irregularities. ‘wo days later (fig. 9, d) shght regressive 
changes had set in. The form was more unified, but the blow- 
out was smaller, and the collars had been entirely, the flagella 
partially, retracted. Gaps in the blow-out appeared, bridged 
by dermal cells. Three days later the blow-out, together 
with all traces of flagella, had disappeared, and four days later 
the mass had still further shrunk, and was apparently covered 
entirely with dermal cells, though I could not be quite sure 
of this. 
The most interesting feature of this is the gradual assumption 
of unitary form by artificial aggregation of cell-masses, which 
