562 MICROSCOPY. 
the case with other fish. The day after their birth they ate raw beef 
shred very small. These ten fish are now nearly six months old 
and are all females; the two old ones have each had young since; 
one had three alive and four dead, the other four alive and four 
dead ; neither of these latter broods lived over a month and were 
unable up to the time of their death to rise from the bottom of the 
aquarium. Between the birth of each litter there was a period of 
about ten weeks. Those which are alive are all females and the 
succeeding litters were to all appearances males. It will be a curi- 
ous circumstance, and a subject for future investigation, should 
` every alternate litter prove to be of an opposite sex to the preceding 
one. No fish have yet been bred from those born in the aquarium 
and therefore it is not known at what age they begin to reproduce. 
C. Fitz Geraro. — Lieut. H. M., 1st W. India Regt., Nassau, 
Bahamas, March 11th, 1864.— Communicated by the Smithsonian 
Institution. 
.MICROSCOPY. 
PHOTO-MECHANICAL Printinc. — Incidentally to a pathological 
report to the Surgeon General, Dr. J. J. Woodward calls attain 
to the familiar disadvantages of the usual means of representing 
in publications the magnified appearance of microscopie objects , 
by etchings, lithographs and woodcuts. All such hand p : 
laborious and wasteful of time if done by the investigator, 
liable to omit the most important points if intrusted to pe 4 
artist. Even the microscopist himself, being unable to repe 
. i - ; ives to be of 
all that he sees, is obliged to select what he penne than 
his R 
importance, and thus represents his own theori 3 
severe facts. [If, however, his theories are correct, 
enables him to give a distinctness and compl f 
lacked by the photographic camera.] The advantage O! % 
i rints afe 
i the side of photo-micrography, but silver PMY m 
ness is on the side of pho graphy, and the reproduction 4 
ired. Two ae 
from the negative by the action of light, 4 
“ intaglio” is produced by pressure. ; 
colored gelatine films, which constitute the prints, 
