98 H. C. VAN DER HEYDE. 



supposed to control the hydraulic pressure in the water vascular 

 system. No rhythmical contraction can be observed. 



The same corpuscles can be seen in a preparation of the above- 

 mentioned water lungs. This makes their respiratory function 

 still more probable. On the other hand the evidence seems to 

 show that also the podia and the tentacles play an important role 

 in the respiration of Thyone, andi that two systems of organs 

 seem to be concerned with one function. 



SUMMARY. 



Hemoglobin is found, bound to corpuscles, in the Po-lian vesi- 

 cle(s), the ampullae and the wall of the water lungs of Thyone 

 briareus, a dendrochirote Holothurian, common around Woods 

 Hole. This fact is interesting in connection with the fact that 

 Thyone is a mud-dweller. 



