ACALEPH/K 
233 
It is a general characteristic of all colonies of polypi that the 
&ge3tive cavities of the individuals composing them meet and mos- 
e,l lato in a common vascular system. The Yilelhs present the same 
conformation. Only in their case the vascular system is extended 
horizontally, this being the essential character ol the union oi all 
jhe individuals constituting the colony, with the canals common to all, 
111 which the nourishing fluids circulate, elaborated for all and by all. 
is a true picture of social communism realised by Nature. 
The central polype is alone destined to absorb the lood. M. "\ ogt 
has always found in its interior cavity fragments of the shells of 
crustaceans, the remains of small fishes ; and he has often seen the 
hard parts which resist digestion discharged through the trumpet- 
hke opening. This central polype nourishes itself and also all the 
°Ihers, hut is itself sterile. 
The tentacles are hollow cylinders, completely closed at the ex- 
hemity. These are strong muscular tubes of considerable thickness, 
l he interior of which is filled with a transparent liquid. They are 
e Uvelopei in a strong membrane of a deep blue colour. The epidermis 
ls furnished with small stinging capsules, formed of a sac with compara- 
bly thick walls. If this sac is compressed under the microscope it 
ex plodes, opening at a determinate part, and throwing out an apparatus 
f° r ming a long stiff filament, which is implanted on a conical channel 
arid surrounded with points. “ I know not,” says M. Yogt, “ if all this 
Machinery can re-enter the capsule after it has exploded , hut 1 
P l 'esume that the animal can extend itself and withdraw at pleasure. 
V- tentacule of Yilella sufficiently compressed presents a surface 
>l istling with these cirri, so as to resemble a brush, ihe tentacles 
fliemselves are in continual motion, and I have no reason to doubt 
bf the observation of Lesson, who saw them cover small crustaceans 
aud fishes, may he perfectly true. These stinging organs doubtless 
serve the same purpose as with other animals of the same class , 
lla mely, to km the prey which the tentacles have enabled them to 
secure.” Thus the Yilellm have their javelins, as the Greek ^ and 
l °nian warriors had and a lasso, as the cavaliers of Mexico and Texas 
have. 
The reproducing individuals form the great mass of the appendages 
attached to the under surface of the Yilella. The form of the in- 
lv idual s is much more varied, inasmuch as they are extremely 
