HOMOGENEA. 421 
other complication, and is frequently destitute of even the ap- 
pearance of a mouth. 
The first tribe comprises those, which, with a gelatinous 
body more or less contractile in its different parts, still pre- 
sent external organs consisting of cilia more or less strong. 
When they have the form of a horn (cornet), from which the cilia 
issue as in the Polypi called Vorticellze, we have the 
Ureovaria, Lam. 
When the body is flat, and these cilia are at one extremity, 
- 
TRICHODA. 
When they surround the whole body, 
LEUCOPHRA. 
When some of them are stout, and represent species of horns, 
KERONA. 
And when these pretended horns are elongated into threads, 
HIMANTOPES. 
The second tribe consists of those which exhibit no exter- 
nal organ whatever, if we excepta tail. In 
Cercaria, Mull. 
The oval body is in fact terminated by a thread. To this genus be- 
long (among others) those animalcules which are observed in the 
semen of various animals, and on which so many fantastic theories 
have been founded. 
When this thread is forked, as is sometimes the case, we have the 
Furcocerca of Lamarck. ; 
