PROCEEDINGS OF SOCIETIES. 103 



for his own part, he had not only been much interested, but had also 

 derived a great deal of information. 



The thanks of the meeting were unanimously voted to Mr. Stewart 

 for his communication. 



Mr. Hickie then exhibited to the meeting a series of photographs, 

 and read letters from Dr. L. Eabenhorst and Herr Seibert on the 

 subject of the strife of Frustulia Saxonica, with a view to prove its 

 complete distinction from Navicula crassinervis, (Mr. Hickie's com- 

 munication will ajjpear in our next number, having been " crushed 

 out " with much other interesting matter.) 



Dr. Lawson inquired if what Col. Woodward stated was correct, 

 viz. that the transverse strife had always a definite number, but that 

 the longitudinal ones varied with alteration of focTis. 



Mr. Hickie said that Dr. Woodward's remark, though new, was not 

 true ; * he could himself do exactly the same with another specimen 

 perfectly well known to all, and if Dr. Lawson would call upon him 

 he would show him exactly what Dr. Woodward had described. 



Mr. Curties hoped that Mr. Hickie would succeed in throwing 

 some light upon the subject as to the species of this object, and 

 would be able to show them how Rhomboides, Grassinervis, and Frus- 

 tulia, when viewed by a proper and suitable glass, could be dis- 

 tinguished beyond the possibility of a mistake of any kind. 



Mr. Hickie said the photographs marked C, D, and E, looked exactly 

 like Grassinervis, because in that the median line ran almost perfectly 

 to the end. In Saxonica it was not so, it was also pinched in at the 

 end, and the ratio of the diameter was greatly in excess in proportion 

 to the length. 



Mr. Shadbolt said that when Mr. Stewart was speaking about 

 Aulacodiscus he was rather surprised to hear that he suggested the 

 probability of these shells coming together in this way accidentally. 

 Of course this might sometimes occur, but they could hardly expect it 

 to do it so as to foi-m a whole column. In examining Arachnoidiscus 

 some years ago, he had not the shadow of a doubt that what he saw 

 there of a similar kind was the result of division. (Drawing made on 

 the black-board in further illustration.) 



Mr. Stewart said he had intended to say that Aulacodiscus did 

 really increase by division, but in the j)articular slide in question the 

 fact of the columns being formed of different sized individuals led 

 him to suppose that in these cases it might be the result of accidental 

 agglomeration. 



Mr. Mayall inquired what evidence there was that the objects 

 photographed in Germany as described by Mr. Hickie were really 

 Frustulia Saxonica. He had seen a great many similar objects, and 

 had obtained the same appearances with i-inch or |-inch objectives, 

 whereas Dr. Woodward's specimens were represented as seen by 

 y^^-inch or y'^g-inch. After looking at the photographs now exhibited, 

 he thought they were of a coarse form of Bhomboides. 



* There can be no doubt that diffraction lines can be produced as Dr. Wood- 

 ward states. — H. J, S. 



