342° Notes and Comments. 
come from new methods of attacking the problems that stil 
remained to. be solved. The most striking recent instance 
of the insufficiency of the evidence of external. features alone 
was Professor. Oliver’s demonstration of the seed-bearing 
nature of certain fern-like plants, based on microscopical com- 
parison of the structure of the cupule of Lagenostoma, with 
the fronds of Lyginodendron, after which discovery confirma- 
tory evidence speedily came to hand from numerous plant im- 
pressions examined by Kidston, Zeiller, and other observers. 
ASPECTS OF MODERN PETROLOGY, 
Mr. Alfred Harker presided over the Geological Section, and 
reviewed the present position of petrology. . In his intro- 
ductory remarks he pointed out that the application of micros- 
copical and special optical methods, initiated some fifty years 
ago by Dr. Sorby, gave a powerful impetus to the study of the 
mineral constitution and minute structure of rocks, and has 
largely determined the course of petrological research since 
that epoch. For Sorby himself observation was a means to an 
end. His interest was in the conclusions which he was thus. 
enabled to reach relative to the conditions under which the 
rocks were formed, and his contributions to this problem will 
always rank among the classics of geology. The great majority 
of his followers, however, have been content to record and 
compare the results of observation without pushing their 
inquiries farther ; and indeed the name ‘ petrography,’ often 
supplied to this line of research, correctly denotes its purely 
descriptive nature. A very large body of facts has now been 
brought together, and may be found, collated and systematized 
by a master-hand, in the monumental work of Rosenbusch. 
Beyond their intrinsic interest, the results thus placed on 
record must be of the highest value as furnishing one of -the 
bases upon which may eventually be erected a coherent science 
of igneous rocks and igneous activity. 
THE INDEX ANIMALIUM. 
The Committee appointed in reference to the Index Generum 
et Specierum Animalium reported that since the Ig10 Report, 
systematic search through literature has proceeded up to the 
letter E. Further, a group of especially troublesome and 
difficult’ books has been dealt with, e.g. :—-Oken’s ‘ Isis,’ 41 
vols., 1817-48 ; Froriep’s ‘ Notizen,’ 102 vols., 1821-50; Ersch 
and Gruber, ‘ Allgem. Encyclopedie,’ 103 vols., 1818-50, and 
many other volumes have been indexed out of the general 
order as asked for or required—as, for instance, the works of 
Jacob Huebner, which are now in Mr. Sherborn’s hands, in 
hope that he may obtain some further information as to the 
dates of their publication. The search for rare literature con- 
Naturalist, i 
