352 BIOLOGY. 



insects may continue to live without them. On the con- 

 trary, the purely aquatic animals appear enabled to live 

 without true respiratory and absorbent vessels. It in 

 fact appears, that lymphatic as well as respiratory ves- 

 sels are wanting in the molluscs, snails, and worms, 

 since the water directly bathes or washes the arteries. 



1977. Animals with both systems of vessels, the un- 

 closed and closed, must be more perfect in structure, and 

 must at once combine worm and insect in themselves. 

 They are insects from having absorbent and respiratory 

 vessels, but worms as having arteries and veins. 



b. Veins. 



1978. The veins are developed as mucus-vessels at 

 the intestinal extremities of the arteries, which absorb 

 the arterial mucus (blood), after it has deposited its air 

 on the tegumentary substance, just as the lymphatic 

 vessels absorb their fluid from the intestine or any other 

 part of the body. 



1979. As the artery is a respiratory vessel that has 

 become self-substantial, so is the vein a similarly con- 

 ditioned, and dismembered lymphatic vessel. In the one 

 it is the lung, in the other the intestine, that has become 

 the free vascular system. But in the proper vascular sys- 

 tem both lung and intestine are repeated, the former as 

 artery, the latter as vein. 



1980. These arterio-lymphatic vessels (veins) neces- 

 sarily convey their arterial mucus or blood into the stem 

 of the original lymphatic system, or the thoracic duct. 

 For every Indifferent must be brought toward the re- 

 spiratory organ. 



1981. The tegumentary lymphatic vessels (absorbents) 

 consequently unite with the arterio-lymphatic vessels 

 (veins), before arriving at the respiratory organ, and 

 pursue their course thither in common, where they 

 pass over into the air-vessels. The usual notion or 

 idea is, that the lymphatic vessels, from conveying 

 their fluid into the veins, should be subordinated 

 to the latter. But the true philosophical view, is of 



