73 



derms we always find very large faeces and a very incomplete 

 digestion — see chapter 9 and 10. 



Note: 1. Griffiths 48) has considered the function of the 

 radial sacs to be partly of pancreatic, partly of excretory nature. 

 The first author who supposed that they have the function of 

 kidneys, was Johan nes Miiller 91). Griffiths demonstrated 

 — see the chapter on excretion — , that uric acid is present in them. 

 After injection of acid fuchsin, indigo-carmine and methyl-green 

 Cuenot found the epithelial cells of the pyloric coeca of A. 

 rubens full of these substances ; this surely proves that they 

 must play some role in excretion. The same thing was observed 

 in urchins ; the cells of the last part of the gut (second curvature 

 and rectum) also appeared to contain these substances. Jordan 

 63) in his paper on the excretory function of the „liver" of 

 Astacus fluviatilis, points out that one must distinguish between 

 the true function of an organ, an accessory function and a merely 

 incidental activity- between: „Hauptfunktion, Nebenfunktion 

 and Nebenerscheinung (i.e. zufallige Reaktion auf zufallige Be- 

 dingungen)". As a matter of fact, there is reason enough to think 

 of an excretory function on the part of these invertebrate „liversi". 

 Kovalevski 75) finds indigo-carmine, injected into Squilla, in 

 their liver, de Saint-Hilaire 111) finds peptones there in 

 crawfishes, so does Bruntz 12) with other substances. Darboux 

 29) finds uric acid and urates in the coeca of Aphrodite and 

 describes ..cellules excretrices" in these organs. For Arachnoidea 

 it has been established with an almost absolute certainty by 

 B e r 1 e s e 5), that their ..liver" has excretory function. He demon- 

 strated uric acid in these livers. Plateau, Bertkau and others 

 also found guanin in them. 



Mc. Munn 93) comes to similar conclusions for Molluscs 

 and decapod Crustacea. Jordan himself finds injected methy- 

 len-blue back in the liver of Astacus. When we remember that all 

 these ..livers" are nothing much more than simple appendages of 

 the mid-gut. serving for the extension of its surface and 

 that the Malphigian tubes, the organs of excretion in arthropods, 

 are also appendages of the mid-gut, except as far as their 

 ontogenis is concerned, we must believe that the mid-gut plays 

 a role of some kind in excretion. Jordan believes that this 

 excretory function, at least in Astacus, is a „Nebenerscheinung", 

 not a true function — just as in the case of the excretion of 

 small quantities of urea, anisoil, alizarin etc. by the mammary 

 glands — . 



Del age 31) is opposed to their excretory function- as far 

 as the physiological injections are concerned, he calls it phar- 

 macology, Cuenot 24) explains the excretion of dyes as due 

 to the desire of the organism to get rid of the excess of water, 

 in which the colored substance has been dissolved. As far as 



