IN THE WATERS OF THE LAKES. 7 



tic seas, these peculiar diatoms would then be found the chief 

 and perhaps the only survivors of our numerous present forms. 



It may be of some interest to state that in the year 1878, at 

 the suggestion of a gentleman in Philadelphia, I sent to him 

 repeated gatherings of diatoms from Lake Erie with a view of 

 introducing the Stephanodiscus niagarae into the fresh waters 

 and clear spring ponds of that locality; but we did not succeed 

 in getting them to live, although they will live for weeks here 

 in a comparatively small amount of water. 



Another matter should be. mentioned, and that is that the 

 character of the filterings taken on the same day varies in differ- 

 ent parts of the city. I have seen forms of diatoms and infuso- 

 ria quite abundant in a filtering made at the store of Mr. Gay- 

 lord, which forms could not be found at all in a filtering which 

 was progressing at my own house during the same time, and 

 other striking instances have been noticed; but as the periodicity 

 of forms is a characteristic always observable wherever the filter- 

 ings are taken, it may be assumed that a continuous series of 

 observations made upon filterings from the same faucet repre- 

 sents fairly well the characteristic of the general source of sup- 

 ply. 



It would be of much interest to supplement the examination 

 of the contents of the water supply with that of dredg ngs or 

 soundings from the sediment of the lake bottom, and I hope 

 eventually to be able to do this. 



