ZOOGENY. 347 



is no point in the skin and none in the intestine, where 

 there might not be an air- and a water-vessel, a respi- 

 ratory and absorbent duct. 



1939. There are therefore numerous vessels, and con- 

 sequently a Vascular system. 



1940. Air- and water- vessel must abut against each 

 other ; because they are polar, because the one leads to 

 this place and the other to that. 



1941. The system of water- and air-ducts can form 

 no closed vascular system ; for they only grow towards 

 each other, as did formerly intestine and skin. 



1942. They would not have originated if both cysts 

 had not separated from each other. These vessels are 

 not therefore to be met with in animals that have no 

 intestine. The transition of the water- into the air- 

 ducts takes place in the higher animals through the union 

 of the thoracic duct with the subclavian vein, which 

 conveys the blood directly to the lungs. 



1943. The vascular system is properly the primo- 

 cellular tissue, which occupies the middle, and at whose 

 extremities the two cysts remain approximated, in order 

 that they may continue to live. 



1944. The vascular is the original system, since its 

 two extremities already carry in themselves the air- and 

 mucus-process, so that branchia and intestine are only 

 to be viewed as peculiarly perfected conditions of these 

 extremities. I would even have developed the vascular 

 system first of all, had not another course been required 

 to render the subject intelligible. 



1945. The first animal cyst is a vessel with two kinds 

 of extremities, whereof, like the plant, one draws its 

 supply from the water, the other from the air ; but in the 

 animal this is effected by its own motion. 



1946. The branchia is nothing but a vascular tissue in 

 the air, the intestine none other than a vascular tissue 

 in the water. -Thus, do I wish that these organs should 

 be understood, and not as mere cystic walls. 



1947. Every point therefore in the intestine and skin 

 absorbs, and thus every part is perforated with infinitely 



