81 



Schultz 116). J our dan 72) also saw these cells loaded with 

 yellowish, refringent granules in the wall of the water lungs. 



It must therefore be considered as definitely established 

 that such elimination takes place, the more because Herouard 

 found definite stomata for the outlet of these phagocytes. 

 Bo r das demonstrated uric acid and urates in them by means 

 of Gar rod's test, Schultz however finds that they do not 

 give a murexide test. Neither are they guanin, as Car us 

 supposed'), nor calcium salts, as Jaeger assumed (De Holo- 

 thuriis, Inaug. Diss. 1833), or carbonates — they do not 

 dissolve in HCl. 



It does not astonish me either, that such elimination takes 

 place, since these nephrocytes leave the body at almost any 

 place where there is a thin wall — as we shall see presently — . 

 That it is not the only way of elimination, however, is proved 

 by the fact, that in many Holothurians — the Spatangidae und 

 Clypeastroidea — the respiratory trees are completely absent. 

 Our own conception of the process of excretion will be dis- 

 cussed later on in this chapter. 



Perhaps all these phenomena can most easily be explained in 

 the following way. All ..Fremdkorper", all foreign bodies are 

 grasped by the amibocytes. AU amibocytes are, as general 

 physiology teaches us, positively chemotropic to oxygen. Con- 

 sequently they will all tend to move towards places where the 

 oxygen tension is highest. Possibly it is even justified to assume 

 a certain „Umstimmung" of these cells after they have taken 

 up the excretion products. 



Now, it is very remarkable indeed that almost all the organs 

 mentioned above as supposed organs of excretion are at the 

 same time organs of respiration. This is true for the papulae 

 and for the water lungs, as also for the „ciliated funnels" 

 (Wimpertrichter) of the Synaptidae where respiratory trees and 

 podia are lacking. These little funnel-shaped organs, attached 

 to the mesenteries in the region near the body-wall, are 

 supposed to maintain a water-current which aids in respiration 

 through the skin. This same fact, the high oxygen tension in 

 the neighborhood of these organs, might account for the accu- 

 mulation of the amibocytes at that particular place, which other- 

 wise would seem strange. This hypothesis would also account 

 for the statement of some authors, among them Chapeaux, 

 that the phagocytes, not only those loaded with injected sub- 

 stances, but also young ones — eventually leave the body 

 through the stone-canal, and madreporite, notwithstanding the 

 fact that the current in this tube is directed inward — this current 

 caused by the cilia of the endothelial lining, is supposed to take 

 care of the internal pressure of the water vascular system — . This 



1) He found this substance in the organs of Cuvier which probably is a 

 mistake (Bordas). 



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