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ZOOLOGY: P. H. COBB 
bacter cells. Judging, therefore, from the very small number of organisms 
which are found in the calcareous sand, Azotobacter, a nitrogen fixing organ- 
ism, seems to be one of the earliest and one of the most numerous organisms. 
The nitrogen fixing power of the soils as measured by the ordinary laboratory 
test in solution cultures, in contrast with their nitrogen transforming powers, 
seem to be as vigorous as those of excellent soils. It is interesting, moreover, 
that the calcareous sand fixed about f as much nitrogen in the tests mentioned 
as the surface soil from the wooded land and about f as much as the subsoil 
of the same land. 
Space does not permit a consideration here of some of the pure cultures of 
bacteria and fungi which were isolated from the soil samples studied. Three 
species of Actinomyces found appear to be new and as yet remain unnamed. 
Some of the common organisms of all soils were found, including bacteria, 
Actinomyces, and fungi. These will all be described in detail in a forthcoming 
paper, mention of which has already been made above. 
It is a privilege to acknowledge again our obligation to Dr. A. G. Mayer 
for his kindness in sending the samples and for his interest in the work. We 
also express thanks to Dr. H. J. Conn and to Dr. S. A. Waksman for assisting 
in identification of a few cultures of bacteria and of Actinomyces, respectively. 
AUTONOMOUS RESPONSES OF THE LABIAL PALPS OF 
ANODONTA 1 
By P. H. Cobb 
Zoological Laboratory, Harvard University 
Communicated by G. H. Parker, June 19, 1918 
Although the ciliary responses of the labial palps of pelecypods have been 
much studied, the muscular movements of these organs have been entirely 
neglected. If one valve of an Anodonta is cautiously chipped off leaving the 
subjacent mantle-lobe intact and the animal resting in the opposite valve, 
the mantle-lobe thus freed may be folded back so as to expose the parts of 
the animal lying within the mantle chamber. In this way the labial palps 
in an almost undisturbed condition may be exposed and worked upon. 
In such a preparation the external palp is to be seen resting on the internal 
one and both are quite flat. If, now, the external palp is touched with a blunt 
pointed instrument, particularly in its mid-dorsal region, the organ quickly 
buckles in on its dorsal edge close to its attachment to the mantle and soon 
after begins to curl from its free tip toward its attached base. On stimulating 
the internal palp, it responds as the external one does. Both palps in respond- 
ing curl away from their opposed faces. The vigor of their response is ap- 
parently proportional to the stimulus. Grains of sand dropped on the outer 
face of the external palp affect it as a slight mechanical stimulus, which calls 
