64 THURLOW C. NELSON 



work with fresh-water forms was done at Madison, using chiefly 

 Anodonta grandis, LampsiUs luteolus, and L. anodontoides. 

 These were collected from the near-by lakes and kept supplied 

 with lake water. The marine species were studied at the summer 

 station at Tuckerton, N. J., which is situated on the natural beds 

 of the oyster, Ostrea virginica. Within a few feet of the labora- 

 tory also occurred the hard clam, Venus mercenaria, and the 

 ribbed mussel. Modiolus modiolus. The bulk of the work with 

 salt water forms was confined to these three species. 



In studying the formation and physiological significance of 

 the style, dissections were made of the living animals. Care 

 was exercised to open the molluscs immediately after removal 

 from the water, and to dissect open the stomach and intestinal 

 walls in such a manner as to interfere as little as possible with the 

 main nerve commissures. Wherever ciliary action was investi- 

 gated the animal was kept in a small troligh under the binocular, 

 supplied with a constant stream of water at the same temperature 

 as that in which it had been living. 



Ciliary currents were traced by the movement of food ma- 

 terial, and also by the introduction of carmine grains or fine 

 sand. 



Some difficulty was experienced in sectioning the style sac 

 since with ordinary methods of fixation the style becomes so 

 brittle that it invariably crumbles. The best results were ob- 

 tained by fixing the material in Bouin's fluid, running up through 

 the alcohols as rapidly as possible, and clearing in wintergreen 

 oil, after which the tissue was imbedded in paraffin. 



The sections were stained in Heidenhain's iron-hematoxylin 

 and counterstained either with eosin, acid fuchsin, or mucicar- 

 mine. Fixation with osmic-acid solutions followed by safranin 

 and gentian violet was very unsatisfactory, due chiefly to the 

 slow action of the fixative on the rather large pieces of tissue 

 necessarily used. 



With Bouin's fluid the fixation of the cilia is almost instan- 

 taneous and, as a result, the separate cilia stand up clearly and 

 distinctly, instead of being in a confused mass as usually happens 

 during fixation. 



