664 THE AMERICAN NATURALIST. [VoL. XXXIII. 
growth and life, of which his master was one of the founders, to a 
wonderful degree of advancement. The work is a summary of the 
ideas with which the readers of Loew’s numerous papers and his books, 
entitled Lin natürliches System der Giftwirkungen and The Energy of 
Living Protoplasm, have already become familiar. 
The theory of Loew starts with the principle that there is a pro- 
found difference between living and dead protoplasm. This differ- 
ence shows itself in the different reactions of living and dead 
protoplasm ; for certain relatively inert substances are fatal poisons, 
whereas they have no effect on dead protoplasm. The essential 
living substance must consequently be chemically an extremely 
unstable, labile substance. This lability depends upon the presence 
of both aldehyde and amido-groups. Such an extremely labile alde- 
hyde as the theory calls for has been demonstrated to occur in proto- 
plasm. Life depends upon the activities of this labile protoplasm. 
The work contains also a theory of albumen formation which has 
simplicity and completeness in its favor, even though every step has 
not been experimentally proved. Another valuable chapter is that 
giving a theory of respiration. Thus, throughout the book the results 
of biochemistry are used for the interpretation of biological phenom- 
ena. It follows that it is a book with which every biologist should 
make himself acquainted. CRD 
Green Amæbæ. — Dr. A. Gruber, of Freiburg i. Br., has maintained 
for seven years a small aquarium originally stocked by a bit of dried 
Sphagnum from the Connecticut valley in Massachusetts. He re- 
ports * that the fauna, which at first consisted of Rhizopoda, Para- 
mcecium, and Rotifera, is now reduced to a single species of green 
Ameceba and Paramecium bursaria. Both of these forms are found 
in considerable numbers, being most numerous during the warmer 
part of the year. Repeated examinations have never as yet detected 
conjugation stages, nor has any indication of division been observed, 
though the latter must take place. Both species are abundantly 
supplied with Zoöchlorellæ, and neither has been observed in recent 
years to partake of food. Indeed, all food organisms have died off in 
the aquarium. The Ameceba still, after the manner of its forbears, 
engulfs the shells of Euglypha and Centropyxis, but these are dead 
and empty. The author infers that by virtue of the commensal 
Zoochlorelle these surviving organisms are living a vegetative life, 
1 Gruber, A. Ueber grüne Amöben, Ber. Naturf. Ges. zu Freiburg, Bd. xi 
(1899), pp. 59-61. 
