94 



The presence of these corpuscles in the water-vascular system 

 in both these species, clearly demonstrates the respiratory im- 

 portance of the latter. Probably this is due to the fact that 

 it connects all the tube-feet which surely have respiratory 

 importance. 



Other statements with regard to respiratory pigments in Echinoderms, 

 e.g. the assumption of such a function for the so-called echinochrome (M c. 

 M u n n. 1 885. 92) ) in Echinus and Strongylocentrotus, are to be accepted 

 with some reservation, Winterstein e.g. could demonstrate, that a solution 

 of echinochrome did not take up any more oxygen than the same amount 

 of sea water. 



The red pigment in Thyone seems to be hemoglobin. The 

 following tests have led the author to this conclusion: 



1 . A small quantity of the liquid was dried on a slide, heated 

 a few times under cover-glass, until bubbles appeared, then 

 cooled. Blue black prismatic crystals could be seen which though 

 not absolutely congruent with the figures of the text-books of 

 biochemistry, were doubtless hemin crystals. 



2. To a solution of one or two drops of 1 "/q benzidine in 

 a large quantity of hydrogen peroxide a few drops of the 

 „blood" were added. A dark blue color developped at once 

 and a foaming to way up on top of the test tube could be 

 seen (peroxidase action). 



3. Laked and centrifuged „blood" showed the typical ab- 

 sorption spectrum of oxy-hemoglobin — one broad band in con- 

 centrated solutioil, two on dilution, one of which can easily be 

 identified with the D-sodium line. 



4. On reduction with Stokes' reagent the single band of 

 hemoglobin could be seen. After continued vigorous shaking, 

 the double band of oxyhemoglobin could be produced again. 



5. A small quantity of the material gave a positive prussian- 

 blue test for iron. 



6. Material treated with KCN and kept in the 37° incu- 

 bator for some time, became orange-yellow and showed the 

 absorption band in the green which characterises cyanhemo- 

 globin. 



From this evidence, I have concluded that hemoglobin is 

 present in these corpuscles. This fact is very interesting in 

 connection with the fact that Thyone is a mud-dweller and 

 thus lives in a medium, in which oxygen is scarce. Though 

 there is still a diversity of opinions as to whether oxygen 

 acts as a store of oxygen or not, it is beyond all doubt that 

 the presence of a respiratory pigment like hemoglobin is a 

 great help in the struggle for oxygen. 



In how far the Polian vesicles act as „movers" of the cor- 

 puscles, as a kind of very primitive heart in that way, or as 

 formers — these organs have frequently been called „ lymph- 

 glands" (Cuenot) — , could not be investigated. The same cor- 



