On a Fresh Water Valved Vaginicola. 207 



than the result of particular sorts of food. If the animal now 

 described is new, it may be called Vaginicola aquatica valvata, 

 thus distinguishing it as belonging to fresh water, and leaving 

 open the question of whether it is to be regarded as specifically 

 distinct from Dr. Wright's marine V. valvata, or merely as a 

 variety, a matter not to be conclusively judged of without com- 

 paring a good many specimens. 



Fig. 1 represents the animals protruded from their tube — 

 one stretched to nearly its full length, and showing its ciliary 

 wreath, the other only partially expanded. Fig. 2 exhibits 

 them retracted with the spiral twist already mentioned. The 

 valve, or door, is so delicate, as very easily to escape observation, 

 except in those parts which have nocculent adhesions. Pro- 

 bably many more instances of valved forms may be discovered 

 if the valves are carefully looked for. For this purpose, the 

 illumination must be good, the light not too strong, and 

 advantageously coming from an achromatic condenser. Excess 

 of light or erroneous direction made the valve invisible in the 

 specimen described, and the clearest portions could scarcely 

 be distinguished in refracting power from the surrounding 

 water. 



Vaginicola aquatica valvata ; tube approximately cylindrical, 

 rounded at bottom, 1 — 100" long. Animal much like V. 

 crystallina, but bigger; when expanded, 1 — 50" long, deli- 

 cately striated transversely ; retreating into its tube with a 

 spiral twist. Yalve reaching the mouth of the tube : when 

 closed, slanting at about 45°. Yalve consisting of a stiff plate 

 of hyaline material, with reduplicated portion acting as a spring 

 to close it. 



