BLOOD 



pin's head, it is full of organs which carry on the various 

 functions of life; and, because the whole tissues are as 

 transparent as crystal, they allow us to watch the proc- 

 esses with perfect ease. Take a peep at it. 



It is a gelatinous sac, of a form intermediate between 

 globular and cubical, flat- 

 tened on two opposite sides, 

 with a sort of wart at the 

 summit and another at the 

 side, each of which is! 

 pierced with a pursed ori- 

 fice. The upper of these 

 orifices admits water for 

 respiration and food; the 

 latter passes through a di- 

 gestive system, and is dis- 

 charged through the side 

 orifice. The digestive or- 

 gans lie on that flattened side, which is furthest from your 

 eye, and are therefore dimly seen. 



The globose body is enclosed in a coating of loose 

 shapeless jelly that passes off from one of the lower cor- 

 ners, and forms a short foot-stalk, which unites with simi- 

 lar foot-stalks from the sister-globules, and all together are 

 attached to the sea-weed. Each foot-stalk has an organic 

 pore, into which a vessel passes upon the body. 



Your attention is first arrested by the breathing sac, 

 with its rows of oblong cells all in wheel-like motion. It 

 is indeed a wonderful object; but for the present neglect 

 this, as we will return to it presently, and direct your 

 consideration to the course of the blood. 



It is" true the fluid which I so name is not red, like 



