120 HANCOCK AND EMBLETON ON 



coccinea, D. verrucosa, D. pilosa, D. hilamellata, D. aspera, D. 

 dej^ressa, but D. tuherculata has been taken as the type of the 

 genus, and as the standard of comparison for the rest. 



The digestive organs come first; the mouth in all the species is 

 a powerful muscular organ, provided with a prehensile tongue, 

 beset with siliceous spines, which, when the organ is fully developed, 

 are arranged in a median and two lateral series ; most frequently 

 the median series is wanting, in those species, in which the median 

 series is not developed, there are two principal forms of tongue, 

 one, as in D. tubercidata, broad, consisting of many rows, the other, 

 narrow and strap like, as in D. hilamellata, with only two rows. 

 In addition to the tongue, certain species possess a prehensile 

 spinous collar on the buccal lip, and some of these have also 

 rudimentary horny jaws. The mode of development of the lingual 

 spines is quite analogous to that of the teeth in the Vertebrata. 

 In that division of the genus of which D. hilamellata is typical, 

 the mouth has, opening into its upper wall, a well-characterised, 

 lentil-shaped gizzard. 



The (Esophagus varies in length and form ; in some it is dilated 

 at its commencement, forming a crop ; in others it is simply dilated 

 previously to penetrating the liver mass. 



The Stomach, has two forms ; one, as in D. tubercidata, is very 

 large, receiving the oesophagus behind, giving off the intestine in 

 front, and lying in front of the liver, the other is received within 

 the mass of the liver, and is very small. 



The liver in all is bulky, mostly bilobed, and variously coloured, 

 and pours its secretion by one or more very wide ducts into the 

 cardiac end of the stomach. 



A small lamellated pouch — a rudimentary. Pancreas is attached 

 in some species to the cardiac, in others, to the pyloric end of the 

 stomach. 



The intestine is short, of nearly the same calibre throughout, 

 rather sinuous in its course, and terminates at a nipple-formed 

 anus in the centre of the branchial circle. 



The reioroductive organs are male, female, and hermaphrodite; 

 the male organs consist of a penis and testis, the latter is connected 

 by its external end to the penis, by its internal to the oviduct. 



