GREA T BRITAIN. 1 5 



and a more delicate lining membrane than that existing in 

 the oesophagus. Its upper or cardiac orifice is usually 

 larger than its lower or pyloric one, while the form of the 

 entire organ is subject to considerable modifications, being 

 usually found in one of the two following divisions : the 

 sip/ional t which somewhat resembles a bent tube, as seen in 

 the lumpsucker, flounder, &c., and most of the plagiostomes ; 

 and k the c&cal, in which it ends in a blind sac, and the 

 pyloric portion is continued from the right side, as seen in 

 the perch, gurnard, weever, &c. An intermediate or tran- 

 sitional form sometimes is present, as in the sea-scorpion 

 and in the turbot. Irrespective of the foregoing, certain 

 other deviations occur which it is not my purpose entering 

 upon, as in the mullet, wherein the muscular walls are 

 thickened, causing it somewhat to resemble the gizzard of 

 a bird, &c. 



Through the pyloric orifice partly digested food reaches 

 the commencement of the small intestines, and we usually 

 find that the distance from the pylorus to the vent is com- 

 paratively shorter in fishes than in most of the higher 

 vertebrata. The length of the intestines differs in different 

 classes of fish, and the intestinal lining membrane may be 

 raised into transverse folds as in the salmon, thus increasing 

 the extent of its secreting or absorbing surface, and which 

 is still further augmented by the secretions of numerous 

 caecal appendages. In other forms we find the intestines 

 themselves convoluted, thus increasing their length as in 

 the carp. The large intestine may be straight, as seen in 

 the sturgeon or chimaera, in which the transverse folds (as 

 observed existing in the salmon) become continuous, and 

 an uninterrupted spiral valve is formed, while the same 

 structure is likewise present in sharks, rays, and their 

 allies, but which may be modified into transverse coils. 



