112 THE AMERICAN MONTHLY [Apr 



It will be useless for me to attempt to report subse- 

 quent observations in detail. I must content myself with 

 giving the general results. In August, 1896, I was away 

 from home for two weeks, and when I returned one of 

 the larger cultures had a chestnut brown film on the sur- 

 face of the sediment that was not there when I went away. 

 These were magnificent specimens of Surirella striatula, 

 larger than any I had ever seen before, and more than 

 double the size of any in the original gatherings or any 

 that I had ever found along the Connecticut shore. To 

 guard against accidents I cleaned up a quantity of these 

 diatoms and made a number of slides. I cannot account 

 for their production in such quantities in so short a time. 

 If it be thought that they might have grown by mul- 

 tiplication from specimens overlooked in previous exam- 

 inations, let it be remembered that under the most favor- 

 able circumstances they could not have increased in that 

 way more than fourfold in that time. If multiplication 

 had been carried on much longer they would most cer- 

 tainly have been discovered sooner. The same argu- 

 ment has nearly equal force against the idea that they 

 were the product of conjugation. They might easily have 

 been produced from spores, but I can scarcely think that 

 such large diatoms could have grown to maturity in so 

 short a time. It is true that the spores might more 

 easily have been overlooked. I am the more diflident 

 about forming an opinion because of my failure to dis- 

 cover the preliminary stages when precisely the same 

 thing happened again in the following spring. 



In April, 1897, another culture suddenly showed the 

 same brown film composed of precisely similar Surirella, 

 but this time in company with an equal number of the 

 very large Amphiprora pulchra. Small Amphiprora had 

 been abundant in the culture, but of this large kind I had 

 not previously found a single frustule. These large Su- 

 rirellas were like those found in the open salt water along 



