114 NEW YORK STATE MUSEUM 



Water vascular system. Frequent reference to the respiratory 

 system has been made during the description of some of the 

 more prominent structures involved. There remain however 

 some points which seem to be worthy of further notice and 

 which are now presented. The 17th hydrospire of figure 2 

 extends into the coelomic cavity more than six times as far as 

 the second; it is also more than 12 times as long as the function- 

 ing new ones. Its area presented for osmosis is therefore at 

 least 36 times as great as that of the smaller ones. This would 

 mean that in order to serve the function of respiration as well 

 as the younger hydrospires, the flow of water would have to be 

 36 times as great. A large sheet charged with carbon dioxid 

 and with the loss of nearly all its dissolved oxygen would be 

 valueless to the organism, yet the continued growth of these 

 old hydrospires would emphatically indicate increase of function. 



That there was an increase of function is also shown by the 

 deposit of exceedingly fine sand or clay colored by limonite 

 which we find to be greatest along the inner edges of the largest 

 hydrospires and which is represented by cross hatching in fig- 

 ure 2. This deposit seems to have been swept in just before 

 death and after the falling of the theca to the sea floor. 



The flow of water was down the brachioles into the brachiolar 

 chambers, which also show the presence of the same yellow 

 deposit on their walls, and from here to a small extent through 

 the openings to the food grooves and so on through the enteric 

 cavities ; but to a very much greater extent (and freed of its 

 food content) through the pores opening into the hydrospires 

 and out at the base of the deltoid. I have before referred to 

 the evidence of greater functional activity at the middle of the 

 base of the deltoids, and the upper row of interbrachials may 

 also be associated with this function. In fact the appearance 

 of this upper row is remarkably suggestive of gradual increase 

 in number at their ends. Whether the hydrospires pass under 

 this row or not is as yet unknown. 



The comparatively slight difference between the older and the 

 newer brachioles and the very probable great difference of water 

 flow in the corresponding hydrospires are suggestive of open- 

 ings connecting each brachiolar chamber with the others of 

 the same row (of which we have already had evidence) and of 

 a marked flow of water through them toward the peristome but 

 remaining outside of the probable covering plates of that area. 

 This arrangement would secure the required greater flow for 



