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most layer of the common flesh (Pl. CXI., fig. 4 d). This off- 
shoot is composed of a soft granular substance, devoid of 
definite structure — the “ sarcode ” of physiologists ; the kind 
of material of which the humble rhizopod is made ; a pulpy, 
semifluid mass, without consistency or stability, capable of the 
strangest behaviour, and actually “ behaving ” like a creature of 
much lower rank than the organism with which it is associated. 
In the compound sarcotheca (I must abandon the elegant 
Italian for the more cumbrous Greek designation) a column of 
sarcode pervades the lower and tubular chamber (PI. CXI., 
fig. 5 y ), and on passing into the terminal cup divides, in most 
cases, into two lobes, which are charged with different functions. 
From the inferior lobes (PI. CXI., fig. 5 b ), when the Plumularian 
is in healthy and vigorous condition, long filamentary processes 
are emitted, extensions of the sarcode mass, bearing the 
closest resemblance to those which an Amoeba pushes forth as it 
moves sluggishly along in search of food. From the top of every 
cup these threads of sarcode stream forth, slowly lengthening 
as they follow the course of the stem or branch, until the plume 
is invested by the living gossamer. The extremity of the ex- 
tensile process is usually closely appressed to the surface of the 
stem, over which it glides almost imperceptibly. In some cases 
the sarcotheca is furnished with two apertures, one terminal and 
the other opening into the calycle, and through the latter these 
strange protoplasmic offshoots are discharged. I think we must 
regard these curious structures as distinct zooids in the hydroid 
commonwealth ; a band of stealthy workers, presenting a strik- 
ing contrast to the vivacious hydrse, stealing along on their 
mysterious errands, and almost unperceived enveloping the 
colony with their slender threads. There seems to be a pretty 
constant efflux and reflux of these streams of sarcode. After a 
time the outflow is stayed, and as slowly as they had advanced, 
the processes are withdrawn, until they disappear altogether in 
the lobes which originated them. This may truly be called a 
marvellous structure, or assemblage of structures. It is as 
though a complex Ehizopodal and a complex Ccelenterate 
organism were bound up together. We have here amoeboids 
and hydrse fraternizing in one and the same commonwealth ! 
The upper lobe of the column of sarcode pervading the tubular 
case (PI. CXI., figs. 4 a and 5 a) plays a very different part. 
It emits no amoeboid processes wrought out of its substance, 
but it bears a special apparatus of its own. It incloses a 
number of long, slender, somewhat bean-shaped thread cells, 
disposed in a cluster within the sarcode a little below the 
summit. From these, when the apparatus is in action, long, 
delicate threads are discharged, that stream upwards from the 
extremity of the sarcotheca. These fine extensile lines are 
