X 



J. DEBY ON THE 8TEUCTURE OF THE DIATOM VALVE. 315 



have, in 1872, Dr. J. J. "Woodward * expressing his views, sub- 

 stantiated by photographs, on the structure of Triceratium , but his 

 written description proves that he had but a very indistinct idea 

 of the real nature of what he had under his eye, and, in fact, that 

 he confounded the inner with the outer surface of the valve. 



Dr. Woodward had not then seen Otto Miiller's nearly exhaus- 

 tive treatise f on the valve of Triceratium, published one year 

 anteriorly, in which the German author gives his opinion that the 

 areolae are closed at the bottom (or internally to the valve) by a 

 dotted membrane ; that the sectional view of the partitions 

 separating, the hexagonal alveolae are " nail-headed," as subse- 

 quently also figured by Prinz and Van Ermengem, and better 

 still by Flogel, and that the upper diaphragm winch closes ex- 

 ternally the areolae is pierced by a central circular orifice. All 

 these details are exhibited in the plate accompanying 0. Miiller's 

 instructive memoir. 



At about the same time we find Prof. Adolf. Weiss reading a 

 paper before the Academy of Sciences of Vienna, \ in which he ex- 

 hibited the complex structure of the valve of Triceratium, which 

 he considers as really " multicellular," each hexagon forming for 

 him a distinct organic cell, and where he tries to explain certain of 

 the microscopical appearances as due to variations in hydration of 

 the cellular substance. These views and others expressed by him 

 cannot seriously be entertained at the present day, and I shall dis- 

 miss them here without any discussion. 



At this period, Mr. J. W. Stephenson, § by a most admirable 

 comparison of the valves of Coscinodiscus mounted dry and in the 

 highly refractive bisulphide of carbon, arrived at the conclusion 

 that the " eye spots " were perforations of the " inner " plate, and 

 that these "eye spots " could be neither concave nor convex films 

 of silica, in which last conclusion he is no doubt right. 



In 1874 Mr. J. W. Morehouse describes the valve of Tri- 

 ceratium as formed of two films, and expresses his belief in their 

 continuity, and that fine markings exist on both the upper and 

 lower diaphragms of the areolae. This last opinion must have re- 

 sulted from an excess of penetration of the objectives used, which 

 showed both films at a time. 



* " The Lens," Chicago, 1872, Vol. i, p. 100. 



t " Archiv. f. Anat. u. Physiol.," 1871, Vol. xv, p. 618. 



X " Sitzb. d. Akad. d. Wiss." Vol. lxiii, Pt. I. 



§ " Month. Micr. Jourl.," Vol. x, 1873, p. 1. 



