152 PALMER : 



Several such occurrences rewarded long observation, and with 

 attention to the matter one of them was distinctly seen to 

 enter the keel at a place where the plasma-strand of the rib- 

 canal did not (as it very often does) choke the entrance. 

 This granule travelled along the base of the keel-canal, and 

 was lost to sight at the next rib. It probably passed behind 

 the protoplasmic strand. Two others, as at G, Figure II, were 

 seen to meet each other midway between two ribs, to remain 

 nearly still for a time, and then to part company. Numerous 

 similar instances were seen, but never without a most intensely 

 concentrated attention (for it is impossible to depict in a 

 figure the delicacy of appearance of these granules) and it 

 could no longer be doubted that such bodies do frequently 

 enter the keel and travel along it. Whether they always con- 

 fine themselves to the base of the keel is another question, 

 and one not easily answered. I saw none elsewhere in life, 

 but the difficulties of microscopical definition at other parts 

 of the keel are greater. Their essential likeness to the 

 " Biitschli granules " was made all the more evident from the 

 lack of relation between their motions and the simultaneous 

 movements of foreign particles along the outside of the keel- 

 cleft. 



Now the large significance attaching to the presence and 

 motion of these granules within both keel- and rib-canals 

 arises precisely from the fact that they are not known to move 

 in this manner except only upon protoplasmic surfaces bathed 

 in cell-sap. This is insisted upon by Biitschli, and their 

 motion is by him attributed to their supposed property of 

 causing a change in surface tension at the contact layer 

 between sap and plasma. We are quite warranted, therefore, 

 in drawing the conclusion that it is upon a protoplasmic 

 strand within the keel that the granules in the keel move, and 

 that this strand, let it be ever so hyaline to all appearance, is 

 in unbroken continuity with the obvious protoplasm of the 

 ribs. There is the further inference, that a layer of sap, or 

 its equivalent, bathes the part of this keel-protoplasm next 



