MaxcuH 8, 1912] 
has accepted the post of dean of the faculties 
of Pennsylvania State College. 
Tue following appointments have been an- 
nounced for the medical department of the 
University of Pennsylvania: Dr. Edward Lod- 
holz is to be assistant professor of physiol- 
ogy; Dr. W. N. F. Addison, assistant pro- 
fessor of normal histology; Dr. George H. 
Fetterolf, assistant professor of anatomy; Dr. 
L. A. Ryan, assistant professor of chemistry 
and toxicology. 
Dr. E. T. Warrrarer, F.R.S., royal as- 
tronomer of Ireland, has been appointed pro- 
fessor of mathematics in the University of 
Edinburgh, in succession to the late Professor 
Chrystal. 
DISCUSSION AND CORRESPONDENCE 
REPLY TO HOLMES’S CRITICISM OF “LIGHT AND 
THE BEHAVIOR OF ORGANISMS ” 
In a review of the book entitled “ Light and 
the Behavior of Organisms,” which appeared 
in this Journal, June 23, 1911 (pp. 964-966), 
the author raised several points that call for 
elucidation. Before entering upon the dis- 
cussion of these points, however, I wish to 
take this opportunity to state my regret in 
having overlooked the work of several in- 
vestigators bearing on some of the subjects 
treated, especially that of R. S. Lillie on the 
reactions of Arenicola larve, to which Holmes 
ealls attention. 
After referring to the numerous attacks 
made in the book in question, on Loeb’s 
theories of orientation, Holmes says (p. 964): 
Mast’s own investigations seem to afford about 
as good support as has been furnished for the 
theory which he so persistently attacks. 
He then gives two cases in support of his 
contention : 
1. No clearer case of orientation through the 
local response of the part directly stimulated could 
well be imagined than the one afforded by Ameba, 
and the author admits that the ‘‘method of orien- 
tation is in harmony with much in Verworn’s the- 
ory and also with the essentials in Loeb’s.’’? But 
he adds that ‘‘it does not, however, support the 
idea connected with these theories, that a constant 
intensity produces a constant directive stimula- 
SCIENCE 
O71 
tion.’? I am not sure that I understand the per- 
tinency of the criticism, for there is nothing in 
the theories of either of these writers which im- 
plies that the actual stimulating effect of any 
directive agency is subject to no variation. 
2. Referring to orientation of Arenicola 
larve he says (p. 965): 
Orientation in this form is apparently as auto- 
matically regulated an activity as one might ex- 
pect according to the well-known theory of Loeb. 
The point at issue here clearly concerns the 
question as to whether the methods of orien- 
tation in Ameba and Arenicola, as described 
in my book, are in accord with Loeb’s theories 
of orientation. To settle this question it is 
of course necessary first of all to understand 
these theories. I say theories, for, contrary to 
my critic’s assumption, there are three instead 
of one, as pointed out in my book, pp. 23-35, 
especially in the summary (p. 54) where the 
following statement is found: 
In 1888 Loeb held that orientation in animals 
is controlled by the direction in which the rays of 
light pass through the tissue. From 1889 to 1903 
he advocated the idea that orientation is controlled 
by the direction in which the rays strike the sur- 
face, or the angle they make with the surface. 
His statements from 1906 to 1909 indicate that he 
thinks that orientation is regulated by the relative 
intensity of light on symmetrically located sensi- 
twe structures on opposite sides of the organism. 
The idea that orientation is the result of 
continuous action of light is common to all of 
these theories and is undoubtedly their most 
important distinguishing characteristic. Loeb 
has repeatedly stated this in unmistakable 
terms. Witness, e. g., the following statement 
found in “Dynamics of Living Matter” (p. 
135): Heliotropism is “a function of the 
constant intensity,” and the same idea ex- 
pressed more fully in the same publication on 
pp. 117-119, 130-131, 1388-139. My critic has 
evidently failed to grasp this idea in spite of 
the fact that I have repeatedly stated it in dif- 
ferent forms in quotations from the references 
just given and others, indeed even to such an 
extent that one of my reviewers objects to the 
repetition as superfluous. 
In order to show that an organism orients 
in accord with Loeb’s theories it is conse- 
