594 S. B. MITKA. 



another. All these circumstances were unfavourable for the 

 proper functioning of their digestive organs. Now, on their 

 arrival at my place, I used to open some fifty at a time, and 

 found the crystalline style in none. I could also at the same 

 time see that their digestive function was naturally enough 

 in abeyance. The remaining mussels I would then put into 

 a fresh-water aquarium, where there was plenty of space, 

 good water, and food material. After two or tliree hours I 

 used to open some fifty more of the same batch, taken fresh 

 from the aquarium. Then I invariably found the crystalline 

 style in one and all of these fifty mussels, and at the same 

 time noticed that the digestive function in them had just 

 begun again. An interesting experiment proving the same 

 thing — that is, the existence of a connection between digestion 

 and the crystalline style — got performed over and over again, 

 one might almost say of itself, in one of my aquaria. This 

 aquarium had a leak, and the water in it would gradually 

 drain away in the daytime. During the night there would 

 not be left sufficient water to enable the mussels to set up 

 the well-known in-going and out-going cuirents and so carry 

 on respiration and digestion actively. On the next morning 

 at about 7 o'clock there would be left no water at all in the 

 aquarium. At 8 a.m. every day for two mouths I examined 

 some twenty mussels, and found the crystalline style in none, 

 and the digestive function in abeyance in them. At about 9 

 a.m. the tap was turned on every day, and the aquarium 

 filled with water. Two or three hours afterwards, on opening 

 twenty other mussels taken fresh from the same aquarium 

 and from the same batch, I invariably found the crystalline 

 style in them all, and at the same time noticed that digestion 

 had begun again in all of them. These observations show 

 conclusively that a functional relationship exists between 

 digestion and the crystalline style, — that the style either 

 somehow aids digestion, or else is a product or waste-product 

 of digestion. And we shall see presently that it aids diges- 

 tion in a very important way. 



(6) But the most convincing, the most irrefragable proof 



