l886.] NEW-YORK MICROSCOPICAL SOCIETY. 159 



notwithstanding the care taken to exclude them in the present 

 instance, some resting spores might have got into the jar, 

 although very few could have done so. 



In due time D produced a plentiful crop of diatoms. The 

 normal species seen in the other jars were found in this one, 

 but they were more robust. Besides them, were diatoms of a 

 small oval form, and one of a slender build with a curve or bend 

 and somewhat enlarged at each end, not unlike a rib (Figure 

 2*^). There was also a large number of very delicate Nitzschice. 

 They were invisible in balsam, but quite distinct in a dry mount. 

 Their tenuity entitles them to the specific name attemmiissinia. 

 Though this experiment gave novel results, it shed but little 

 light on the question of motile and resting spores. 



The month of May had come, and my official duties kept me 

 much from home. The propagating jars were all left undis- 

 turbed in the study window until Fall, receiving meanwhile an 

 occasional inspection. It occurred to me to try one more ex- 

 periment. A fresh supply of water was procured from the Bay 

 where the demijohn had been filled. A jar filled with this, 

 marked E, was set in the window. In it was a small living frond 

 of the sea-lettuce, Ulva latissivia. Two months passed, during 

 which not a diatom appeared. Evidently that water was spore- 

 less. 



The six experiments herein detailed were virtually completed, 

 and it was now well on in January, 1884. Begun in December, 

 1882, the series had occupied my attention for a little over two 

 years. For fourteen years had the water which I used been kept 

 in a vessel closely corked and in complete darkness. Perhaps 

 I ought to have published my work at the conclusion of the six 

 experiments. I was urged to do so, but determined not to go 

 into print until I had made a second series of experiments in 

 order to correct or confirm the previous ones. 



The old jars were guarded with zealous care, and occasionally 

 examined until the Spring of 1886, when I began the new ex- 

 periments. The first series of jars had the advantage of being 

 kept in a window with a south-eastern exposure, thus receiving 

 the stimulus of direct sunlight. In April, 1886, I changed my 

 residence. Except during this removal, the jars had not been 

 disturbed. Having put these old jars in a favorable place, I 

 began five more experiments, using similar jars and lettering 



