1893.] Bacteriology in its General Relations. 1061 
it into lactic acid. When grown continuously on solid media 
it likewise loses the power to peptonize or liquefy gelatin, a 
character of such importance that it is used as a basis for 
classification. 
This variation of function is very marked in the case of 
some of the marine bacteria. 
One Mediterranean species, Bac. halophilus, grows only with 
the greatest difficulty on media that contains less than the 
normal percentage of salt in sea water, while on media made 
with sea water it thrives luxuriantly. Constant cultivation 
however on ordinary media finally so changed its habits that 
in the course of twenty generations, it flourished as vigorously 
-= when supplied with fresh as with salt water. 
Another case has recently come under my notice that pre- 
sents even a more marked change. Cladothrix intricata, a com- 
mon form in the Mediterranean mud was first isolated some 
18 months ago. It then manifested no particular preference 
as to the amount of salt necessary for development, growing 
equally well on fresh as on salt water media. Since its isola- 
tion, it has been kept in stock on agar made with distilled or 
tap water. Thisseason when an attempt was made to transfer 
it again to sea water media, it failed to grow. At first, I 
thought the original stock culture dead, but examining it 
microscopically I found that all vegetative forms had died,, 
leaving innumerable spores. Seeding an ordinary agar tube 
from this spore-bearing stock, within 24 hours a copious char- 
acteristic growth of the germ was obtained. A second attempt 
to transfer the germ from the fresh culture, containing only 
vegetative forms was equally unsuccessful. In this instance, not 
only had the organism lost the ability to germinate when sup- 
plied with salt water food but even the vegetating bacilli died 
when introduced into this medium. This might not be sur- 
prising in ordinary terrestrial or fresh water saprophytes, but 
in a form originally a marine species, it shows a marked mod- 
ification of nutritive conditions. 
Examples like the above indicate that physiologieal and 
morphological modifieations are so closely related to the 
environment of the species that it seems almost impossible to 
