RECORDS OF MEETINGS 401 



the particles within the solution polarize the light and thereby render 

 them visible as scintillations against a dark background. By means of 

 this instrument, solutions which appear perfectly homogeneous by means 

 of the ordinary microscope are shown to be composed of particles in sus- 

 pension. Bodies approaching the dimensions of molecules can be made 

 visible. Colloidal solutions have been analyzed by means of the ultra- 

 microscope and shown to be suspensions of particles in a homogeneous 

 medium. Thus, colloidal gold and platinum are resolved into such 

 pseudo-solutions. Albumens fall under this heading, and studies of their 

 nature have shown that they are not homogeneous in solution but are 

 rather fine suspensions. The ultra-microscope as first devised has been 

 modified so as to be adapted to the study of living bacteria. The sub- 

 stage condenser of a microscope is replaced by one where the lens, in place 

 of being bi-convex, is parabolic, and a stop is placed in the centre of the 

 disc so that no direct rays pass to the eye but only those that have been 

 polarized by the bacteria which receive the rays that are sent through 

 them horizontally. The bacterial flora of teeth was shown. Spirochaetes 

 and rodforms are seen, and their locomotor organs are made visible. 



The paper was illustrated with demonstration of apparatus. 



Mr. Brown presented a few brief notes from a forthcoming paper, as 

 follows : The anatomy of Hesperornis as known from described material 

 was discussed and compared with a skeleton recently mounted in the 

 American Museum. In this specimen, for the first time, a complete tail 

 is known. The swimming pose here chosen is accepted as the one that 

 best represents its aquatic habits and more nearly conforms to the struc- 

 ture of the limbs. The peculiar arrangements of the palate bones in 

 Hesperornis and the contemporary Baptornis were shown to constitute 

 •characters that distinguish them from all known birds. Two new speci- 

 mens have made possible a paper restoration of Baptornis which in some 

 characters is more primitive than Hesperornis. The striking features are 

 the complete fibula, heretofore known only in Archceopteryx, and a very 

 long tail, of which fourteen vertebrae are preserved. There were at least 

 sixteen. This is complete though reduced in size. The palate bones are 

 like those of Hesperornis. 



The paper was illustrated with lantern slides. 



The Section then adjourned. 



L. HUSSAKOF, 



Secretary. 



