ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 677 
illumination of tlie object is determined. The other operations are as 
before. 
Of the three excellent plates iii photogravure at the end of the book, 
prepared by*Riflfarth of Berlin and Albert of Munich, the first gives a 
perspective view of the optical bank and its connection with the lantern 
and front wall of the dark room. The second and third are photographs 
of sections taken on Eastmann paper. Plate II. is the frontal section 
through head and neck of a human foetus of the fourth month ( X 9). 
Plate III. is a section through the spinal column of a four weeks’ 
human embryo (x 210). 
Use of Photography in Natural Science.* — Prof. G. Marktanner- 
Turneretscher discourses on the various ways in which photography can 
assist in scientific work. He first takes the case of museums and 
scientific institutions, and points out how useful for the zoologist 
photographs of rare and type specimens would be. More especially 
serviceable would be photomicrograms of minute specimens. Whole 
groups, such as the Protozoa, which are too small for exhibition, could 
thus be brought to the notice of the public. Such photomicrograms 
would be also of great assistance to the scientist himself, since they can 
be compared with other specimens &c., without the necessity of bringing 
the object itself again under the Microscope. If each scientific worker 
had photographs of his species arranged as a catalogue the task of 
comparison of new with already known forms would be considerably 
simplified, and many synonyms would in this way be avoided. As 
regards the palaeontological departments of a museum, the less perfect 
specimens should be accompanied by photographs of the more perfect 
individuals which had been figured. 
The value of photography and more especially of photomicrography 
to the histologist and embryologist is seen in the constant use which 
they make of it, as shown by the numerous photographic plates which 
invariably illustrate their published works. 
In botanical researches photography has also been of the utmost 
service, as, for example, in the recent investigations of Paul Knutt on 
the fertilization of flowers by insects. He found that certain flowers 
with little colour produced a considerable effect on the sensitive plate. 
He explains this as due to the reflected ultra-violet rays, and considers, 
from the fact that such flowers are sought after by insects, that the 
insect eye is sensitive to these rays. 
In mineralogy and petrology photomicrograms of sections in ordinary 
and polarized light are of great use. Each rock specimen exhibited in 
a museum should be accompanied by a pliotomicrographical representa- 
tion of its section. 
In teaching establishments photography is more particularly of 
service by the methods of projection. 
The author concludes with advice as to the most suitable photo- 
graphic apparatus to be used for different purposes. As regards photo- 
micrography he recommends the use of Zeiss’ apochromatics and 
projection eye-pieces for work with high magnifications. 
* Mittheilungen d Section f. Naturkunde des O. T.-C., iv. (1892) pp. 33-5 and 
41-44. 
