1000 
In the case of some plants, particularly maize 
and other Graminee, ammonia is by no means of 
inferior value to nitric acid, for Mazé was able to 
obtain as great an increase in dry weight in 
maize, using at most a one half per cent. solution 
of ammonium sulphate, as when he supplied it 
with a solution of a nitrate. Similar results were 
obtained in cultures of Brassica and species of 
Allium. Forest trees also must be dependent on 
ammonia, since nitrates are seldom present in 
woodland soils. 
So far as we know at present it is quite certain 
that in addition to plants which definitely prefer 
nitric acid (€. g., buckwheat, potatoes, turnips) 
there are others which get on just as well or even 
better with ammonia. 
Perhaps after all the most conclusive proof 
that plants in nature can do well without ni- 
trates comes from the fact that certain peat 
soils have been shown to be devoid of nitrates, 
yet they amply support plant growth. Again, 
rice responds well to ammonia even in soils 
where no nitrification can be detected. 
Also it is true that we, as well as other in- 
vestigators, have shown that soils very low in 
nitrification may be very productive and that 
on such soils plants respond readily to organic 
matter or ammonia, indicating that nitrifica- 
tion is often not an essential factor to soil 
fertility. 
The general conclusion regarding the availa- 
bility of ammonia and nitrate-nitrogen is that 
both can be used by many plants; that often 
nitrate nitrogen applied in the field gives 
larger crop yields. But the relative availabil- 
ity of these nitrogenous substances for crop 
plants under natural conditions has not yet 
been determined. This is an essential desid- 
eratum. A question that must be answered 
conclusively before we can know the signifi- 
cance of nitrification and dentrification. 
Tt seems after all that ammonification is the 
essential thing and that nitrification is rela- 
tively unimportant, but this is only indicated, 
not proved. 
There is need of rigid proof as to the rela- 
tive availability to each crop plant of am- 
monia and of nitrate nitrogen. Then we shall 
know the true importance of the problems of 
nitrification and of denitrification. Following 
SCIENCE 
[N.S. Vou. XXXV. No. 913 
this knowledge will come the questions of cor- 
recting such evils as need correction, the 
heightening of nitrifying power in cases 
where this is low and where higher nitrification 
would be of advantage; the lowering of deni- 
tratation if this be a disadvantage and where 
it is a disadvantage. 
Plant physiology must join hands with soil 
bacteriology to ascertain which are the sig- 
nificant problems that conditions of deficiency 
may receive correction. 
F. L. Stevens 
COLLEGE OF AGRICULTURE, 
MAYAGUEZ, Porto Rico 
REACTIONS OF YOUNG LOBSTERS DETERMINED BY 
FOOD STIMULI 
Ix recently glancing through some old notes 
written several years ago, when the writer 
was interested in problems relating to the be- 
havior of the larval lobster (Homarus ameri- 
canus), certain unpublished data regarding 
the reactions to food-stimuli came to light. It 
is the aim of the present note to give some of 
these data, which may be regarded as supple- 
mentary to the material published in 1908, 
terminating the writer’s investigations on the 
subject of behavior of Homarus. 
Many students of animal behavior have 
learned that the condition of hunger is able to 
greatly modify the reactions of organisms to 
many stimuli—especially to food. Generally 
speaking, it has been found that hunger pre- 
vents the manifestation of certain normal 
types of reaction. The effect of hunger upon 
certain stages of Homarus is no exception to 
this rule. In this instance, however, the con- 
dition of hunger has been thus far found in- 
strumental in modifying the reactions of the 
lobster only in the fourth and later stages, for 
similar experiments upon lobsters in the 
earlier stages have not yet been made. One 
reason for this is the fact that the larval 
lobsters of the first three stages are not able to 
direct their own activity in a definite direc- 
1<<The Behavior of the Larval and Early Adol- 
escent Stages of the American Lobster (Homarus 
americanus) ,’?’? Journ. Comp. Neurol. and Psychol., 
1908, 18, (3), 199-301. 
