METAMOKPHOSES OF ACHTHERES. 



425 



(1092.) As we might suppose, from the nature of the food upon 

 which this creature lives, the alimentary system is extremely simple. 

 The oesophagus (the course of which is represented by dotted lines in 

 the same figure) terminates in a straight digestive canal (fig. 221, a), 

 which passes through the centre of the abdomen ; but no separation 

 between stomach and intestine is 



visible. The entire tube, from the Kg. 221. 



transverse constrictions visible 

 upon its surface, has a sacculated 

 appearance, and is perceptibly 

 dilated towards the centre of the 

 abdominal cavity ; after which it 

 again diminishes in size as it 

 approaches the anal orifice (6), 

 situated at the posterior extremity 

 of the body. 



(1093.) Near the termination 

 of its course, the alimentary canal 

 passes through a loop formed by 

 transverse bands (n n), and, more- 

 over, seems to be retained in its 

 position by radiating fibres, appa- 

 rently of a ligamentous character, 

 but which have been described as 

 representing a biliary apparatus. 



(1094.) The muscular system 

 of this animal is far more perfect 

 in its arrangement than in the 



preceding classes, and the delicate fasciculi which move the rudimentary 

 limbs are visible through the transparent integument (fig. 219). In 

 the abdomen, the muscles form longitudinal and transverse bands that 

 intersect each other at right angles (fig. 221, d) an arrangement not 

 very different from what we shall soon meet with in the rotiferous 

 animalcules. 



(1095.) The nervous system appears to consist prnicipally of two long 

 filaments (fig. 221, c) that run beneath the alimentary canal : but it 

 is extremely probable that these communicate with some minute ganglia 

 in the neighbourhood of the head ; at least, the perfect structure of the 

 oral apparatus and the development of the limbs would seem to indicate 

 such a type of structure. 



(1096.) The generative organs in the female Achtheres consist of two 

 parts the ovaria, wherein the eggs are formed, contained in the abdo- 

 minal cavity (fig. 219, d (T) and of two external appendages, or egg- 

 sacs (fig. 219, //), which are attached to the posterior extremity of the 

 body, for the purpose of containing the eggs until their complete de- 



Viscera of Achtheres Percarum: a, alimentary 

 canal ; 6, anal orifice ; c, nervous filaments ? ; 

 d, muscular bands ; e, unimpregnated, and f, im- 

 pregnated ovary ; g g, external openings of the 

 ovaria. 



