59 



The contrary of course happens when the lantern is pulled inward. 

 It looks to me as if there is a great analogy between the 

 movements which I described above and those described by 

 Gem mill. It seems to be a general reflex of the urchins if 

 taken out of the water ; perfectly purposeful in case the 

 ventral side is down, but senseless if the animal lies on its back. 



Whether or not these same movements play a role in respiration, when 

 the animal is under water, has not been proved experimentally, but it 

 seems probable from the description of von Uexkiill. In the chapter 

 on the respiration I shall . describe the so-called internal gills of the urchins. 

 These baggy prolongations of the peristomium are filled with water when 

 the lantern is raised and the water is expelled, when the lantern is lowered. 

 One indication in favor of their respiratory importance is that in water with 

 low oxygen-concentration the animals move their lantern up and down 

 without changihg their position. Interesting from the general physiological 

 standpoint is the fact that these movements seem to follow van 'tHoff's 

 rule with regard to temperature, as Roaf has shown 108). 



Returning to our injection experiments, we may say that 

 in the case of proteins a strongly positive ninhydrin-test after 

 a little more than an hour showed that they have actually been 

 broken down .and resorbed and that the perivisceral fluid has 

 the function of conveying them to the tissues. 



In the case of the sugar injections I have never yet succeeded 

 in demonstrating glucose in the perivisceral fluid by means of 

 Fehling's test. This may be due to several circumstances. 

 Possibly the larger part is „burned up" in its passage through 

 the intestinal wall, as Cohnheim assumes for the case of 

 Holothuria ; it may also be due to the quick resorption of this 

 substance from the perivisceral fluid, which we will discuss in 

 chapter 22. 



About the resorption in Holothurians we have two studies 

 at hand, and strange enough the two authors contradict each 

 other in nearly every detail. Cohnheim 17) was the 

 first to attack this problem, Enriques 37) in the Archivip 

 zoologico discusses his results and comes to absolutely different 

 conclusions, notwithstanding the fact that both authors worked 

 on exactly the same species. 



Enriques' paper came too late to my attention: in that 

 way I was not able to perform any but very superficial ex- 

 periments on this question ; since however it seems to me that 

 this problem has enough importance, I may be justified in giving 

 here a short summary of their controversy. 



One of the chief points of their discrepancy is the question 

 of the function and importance of the „blood (i. e. the lacunar)" 

 system. Cohnheim does not pay any attention to it and 

 simply states, „dass bei den Seeigeln und Holothurien jede 

 Circulation iiberhaupt und imbesondere jede circulatorische Ver- 

 bindung zwischen dem Verdauungskanal uud dem iibrigen Korper 



