QUEKETT MICROSCOPICAL CLUB. 539 



recent notes. But I certainly cannot agree that these structures 

 are myths without substance. I still maintain that they are 

 very real structures. I take it that if they were interference 

 figures, they could only be formed when the dots from which 

 they are supposed to emanate are regularly placed, equally spaced 

 and of the same size, also that under different conditions of 

 illumination or the shifting of the mirror they would alter their 

 position or form. But this is by no means the case. In most 

 diatoms the dots are regular in position and size, but on some 

 portions of the shell of Nitzschia scalaris regular rows of small 

 dots and diverging rows of much larger dots may be found side 

 by side, and some of the dots in the diverging rows are often 

 quite irregularly placed, yet the structures I suppose to be pores 

 are regularly placed along the middle of the space between the 

 row r s in each case, or, where very widely diverging, the row of 

 pore-structures forks. Also they do not shift their position 

 under varying conditions of illumination ; they can be seen alike 

 and in the same position with axial illumination and a full cone 

 or small cone of light, with annular illumination, with oblique 

 illumination in one azimuth arranged either parallel with or 

 transverse to the rows of dots, with either a chromatic Powell 

 and Lealand or an Abbe, or an achromatic Powell and Lealand 

 substage condenser. Surely identical myths could not be pro- 

 duced under all these conditions." 



Mr. Ainslie, while pointing out the impossibility of any 

 detailed criticism until opportunity had been obtained for care- 

 fully going through the statements, remarked that size alone by 

 no means determined the limits of visibility : the quality of an 

 object, its opacity or transparency, and other factors, would 

 affect the matter. He gave some instances where structures had 

 been distinctly seen which were far smaller than what is 

 scientifically considered the minimum required for visibility. On 

 the proposal of the Chairman, a very hearty vote of thanks to 

 Mr. Merlin for his valuable communication was recorded. 



Mr. Rousselet exhibited under microscopes two species of African 

 Volvox. These had a somewhat remarkable history. In October 

 1910 a paper by Prof. G. S. West, of Birmingham University, 

 was read, in which two new species of Volvox from Africa are 

 described. One, V. Africanus, had been collected by Mr. It. T. 

 Leiper, of the Egyptian Government Survey, from the north part 



