LESSON 48.] NUTRITION IN FISHES AND EEPTILES. 



167 



FIG. 267. 



732. It is an inconceivably pretty sight to see a Cuttle-fish blush 

 blushing is by no means limited to them, for other naked (shell-less) 

 molluscs do the same occasionally, but 

 in an inferior degree. "When one of these 

 creatures is brought on deck from a 

 dredge, and placed in a dish of sea- 

 water, after a few minutes the whiteness 

 of its skin will disappear, and its entire 

 body and tentacles become suffused with 

 a pale pink color, which gradually be- 

 comes somewhat intensified : this is the 

 blush. 



Left to itself, the animal will soon 



resume its former color ; it is, however, easy to kill them preserving 

 the blush permanently in death. 



Section of Cuttle-fish bone, mag- 

 nified 100 diameters. 



LESSON XLYIII. 



NUTRITION IN FISHES AND EEPTILES. 



733. For the most part, these animals are predaceous, and swal- 

 low their prey entire ; their oesophagus is consequently short and 

 wide, their stomach capacious, and their intestine short. 



734. Their accessory glands are moderately developed, and their 

 teeth are adapted to prehension rather than mastication ; of the 

 structure of these organs, more will be said hereafter. 



735. The alimentary canal of fishes is generally more short and 

 simple than in higher vertebrata, which agrees with their predatory 

 habits, and their inferior position in the scale of being. 



736. With a short oesophagus and a capacious stomach, with its 

 two orifices approximated, the whole digestive canal of fishes is often 

 shorter than the body, as seen in the common Herring (Glupea ha- 

 rengus), Fig. 268, where the narrow cardiac part of the oesophagus 

 (a) opens into a lengthened tapering stomach (5), communicating by 

 a long duct (m) with a large air-bladder (I). The duodenum, c 

 (twelve ; so called because the human duodenum is about twelve 

 fingers in length ; it is the first of the small intestines), is provided 

 with numerous pancreatic tubuli (d), which remind us of the eight 

 similar follicular appendages beneath the crop in the Cockroaches. 



