ACALEPHA. 479 



suckers, sometimes resembling ears or ligulse. Those that are known are very 

 small and inhabit fishes. 



FAMILY IV. 



CESTOIDE^:. 



THE fourth family comprises those which are destitute of external suckers. 

 But one genus is known. 



LlGULA, Block. 



Of all the Entozoa, these appear to be the most simply organised. Their 

 body resembles a long riband ; it is flat, obtuse before, marked with a longi- 

 tudinal stria, and finely striated transversely. No external organ whatever is 

 perceptible, and internally we find nothing but the ova, variously distributed 

 in the length of the parenchyma. 



They inhabit the abdomen of certain birds, and particularly of various 

 fresh-water fishes, enveloping and constricting their intestines to such a 

 degree as to destroy them. At certain periods they even perforate the parietes 

 of the abdomen to leave it. 



CLASS III. 



ACALEPHA. 



OUR third class comprises Zoophyta, which swim in the waters of 

 the ocean, and in whose organisation we can still perceive vessels, 

 which, it is true, are generally mere productions of the intestines exca- 

 vated in the parenchyma of the body. 



ORDER I. 



SIMPLICIA. 



THE simple Acalepha float 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 evidently originate from the stomach, and do not 

 occasion a true circulation. 



