374 ACALEPHA. 
CLASS ITI. 
ACALEPHA. 
Our third class comprises Zoophyta which swim in the 
waters of the ocean, and in whose organization we can still 
perceive vessels, which, it is true, are generally mere pro- 
ductions of the intestines excavated in the parenchyma of the 
body. 
ORDER I. 
SIMPLICIA. 
The simple Acalepha fioat and swim in the ocean by the 
alternate contractions and dilatations of their body, although 
their substance is gelatinous and without any apparent fibres. 
The species of vessels observed in some of them are hollowed 
out of their gelatinous substance ; they frequently and evi- 
dently originate from the stomach, and do not occasion a true 
circulation. 
Mepusa, Lin. 
The Medusz are furnished superiorly with a disk more or less 
