PROCEEDINGS OF THE SOCIETT. 713 



chiefly of two species. He had them in a little 1-oz. phial, and both 

 •were living on some algae at the time he obtained them. At the end 

 of a week, however, one species died, the conditions not seeming to 

 suit it. About that time he had to go away for two months, and on his 

 return he found that the remaining species [Nitzschia) had increased 

 astonishingly. On looking at the bottom of the phial to find the 

 others, he was surprised to discover no trace of them, they had all 

 been dissolved, and their substance had gone to feed the Nitzschice, 

 which went on growing for seven or eight months until there was no 

 more silica left in the water. When they could get no more, a rather 

 curious thing took place — they became a little bow-shaped, and then 

 by-and-by they got more so, until at last if some persons had found 

 them there would have been perhaps half-a-dozen new species made 

 out of them. "When they could get no more silica they died off also. 

 He thought, therefore, that silica could be dissolved, and could 

 become silicate of soda in sea- water by some process which they knew 

 not at present, 



Mr. Michael said it struck him as being a singular thing that 

 almost all the borings from the outside were at right angles to the 

 central canal. This was so marked, that it seemed to be something 

 more than an accidental circumstance. The borings also, in almost 

 every instance, went up to the central canal, but did not cross it. 

 One appeared to have commenced from the inside and not to have 

 reached the esterior, but it was still at right angles to the central 

 canal. The enlargement did not usually commence exactly at the 

 boring, but at some distance from it. If they were borings, he 

 thought they must have been done under some circumstances which 

 had not yet been traced. He should like to know if the President 

 could explain any of these facts, particularly that some seemed to be 

 bored from the interior, and that the enlargement was not at the 

 boring, but at some distance from it. 



The President, in regard to Dr. Millar's remarks, said that Dr. 

 Bowerbank proved that the most soluble part of a spicule was the 

 portion in contact with the axial canal, and that potash acted more 

 quickly upon it in that part than at any other. At the same time, he 

 might say that there were other specimens shown which were being 

 dissolved and ruined from the outside as well, Mr. Deby's remarks, 

 he thought, rather supported him ; they all knew that silica was 

 soluble, but they did not know how its solution was effected. Carter 

 had noticed the borings, but as regarded their direction it would be 

 found that every now and then they got one which was oblique. It 

 seemed that they opened out into the axial canal, and the axial canal 

 itself was invariably enlarged ; the erosion seemed to take place from 

 within directly the penetration was effected. They had very few 

 instances of obliquity. He concurred with Mr. Carter that they did 

 not come from within. The first thing established was the broken- 

 down condition of the axial canal. 



Mr. Crisp said there was to have been a discussion that evening 

 on swinging substages, the value of which Mr. Crouch disputed. 



