254 THE AMEKICAN MONTHLY [November, 



Now, in these tufts of Melosira the shorter filaments are as 

 much smaller in diameter as they are shorter in length, and they 

 contain about the same number of individual diatoms, and, as 

 would be inferred from this, according to my observations, they 

 all commence growth at the same time ; consequently the great 

 difference in size cannot be a result of repeated subdivision. 



A small pond in Bristol, Conn., is very rich in diatoms; in 

 one gathering from the upper margin of this pond I found an un- 

 usual form of Pinnularia. It was nearly the size of Finn, major, 

 but did not separate after division ; so that it formed long ribbon- 

 like filaments containing as many as thirty-two and sometimes 

 sixty-four individuals, all apparently of the same size ; careful 

 measurements failed to show the slightest difference in size. 



In the rapid current just above the tide gate at Morris Creek, 

 growing on stones constantly submerged, but subjected to changes 

 from salt to brackish water at every tide, is a peculiar Polysi- 

 phonia I' have never found elsewhere. The filaments are very 

 fine, about two inches long, of a very dark hair-brown color ; im- 

 mersion in fresh water has little effect upon it. I have kept it 

 for two days in fresh water without any more apparent change 

 than the difference in temperature would cause ; this seems re- 

 markable, as other Polysiphonia immediately discharge their 

 coloring matter and decay upon being placed in fresh water. 

 This growth extends up the stream into the borders of the Melo- 

 sira, where they grow together. 



In the latter part of summer, and particularly in September, 

 the ditches of this section are covered with a floating scum con- 

 sisting largely of Algaj and oscillaria, but containing vast numbers 

 of apparently minute diatoms. Last autumn I found the mud at 

 Leete's Island Creek at ebb tide covered with a rich brown coat- 

 ing extending over many square yards of surface ; these were 

 also minute diatoms, of Navicula shape, going through the char- 

 acteristic motions with surprising activity. 



Last month I found a similar coating on the mud at low tide 

 in a ditch leading from the moat at the rear of Fort Hale, New 

 Haven harbor. These were similar to the others, but contained 

 also large numbers of small Fleurosigma, which were, however, 

 many times larger than the forms making up the bulk of the 

 deposit. 



These forms I cannot class with any described varieties, and 

 the fact that they contain so little silex as to be completely dis- 

 solved by acids causes me to regard them as young diatoms 

 developing from spores. Unfortunately I have been unable to 

 visit the localities in such consecutive order as would be neces- 

 sary to trace their development in their native habitat, and every 

 attempt at artificial culture has so far failed on account of the 

 rapid multiplication of large ciliata which devour them before 

 they have time to grow. I have not yet discovered any method 

 of freeing a gathering containing them from their devourers, and 



