190 
and calorimetric analyses which were carried 
out in. Budapest. 
Determinations of the chemical energy— 
heat combustion—in known quantities of the 
material were made by means-of the bomb 
calorimeter, strictly according to the rules of 
modern calorimetry. Small (practically, be- 
tween 15° and 25° C.) calories were recorded. 
Concerning the applicability of thermochem- 
ical methods to the study of embryogenesis, 
nothing need be said at present except that 
indirectly the work of Rubner and others, 
while directly that of Tang] and his students, 
can leave no doubt on this point. 
Comparison between the fertilized egg and 
the hatched embryo of Fundulus disclosed a 
discrepaney in chemical energy which can be 
in no wise interpreted as an analytical error. 
Thus briefly summarizing the results, it was 
found that 
Calories 
1,000 fertilized eggs of F. heteroclitus con- 
(AES! codcoaungaggoeongoodoDOO OOOO 3,264 
1,000 hatched larve of I. heteroclitus con- 
TNE BoboooopDOode COD DOO ODCGCCODO OOD 2,550 
Transformed during development ......... “710 
Tf loss of energy during development is to 
have any special significance from the stand- 
point of embryology, it must be shown that no 
substances rich in chemical energy diffuse out 
of the egg during the period under discussion. 
This seems to be true of Hundulus, for the 
nitrogen content of the egg remains constant 
up to the 240th hour, and probably for the 
whole developmental period. In the case of 
the frog also, no substances appear to diffuse 
out of the egg, for the ash content remains 
the same from the beginning of the develop- 
ment to the end. The same thing has also 
been proved for the trout, the chick and the 
silkworm (Tangl and Farkas). The only al- 
ternative therefore seems to be that the dis- 
crepancy in chemical energy between the end 
and beginning stages of development is due to 
the transformation of chemical energy into 
heat, or other forms, and not to the diffusion 
of energy-containing substances out of the egg. 
During the developmental period, 384 hours, 
during which 1,000 eggs of F. heteroclitus 
SCIENCE 
[N.S. Vou. XXXV. No. 892 
lose 710 calories of chemical energy, larve are 
produced whose organic substance weighs in 
the neighborhood of 0.2 gram. If now the 
amount of energy lost is divided by the 
amount of organic substance produced and 
multiplied by ten, 710/.200 < 10, we get 3.6 
large (kilogram) calories—an amount which 
expresses the specific work of development, 
namely, the amount of chemical energy trans- 
formed during the production of one gram of 
organic substance of F’. heteroclitus. 
The further discussion of these results, as 
well as of many subordinate questions con- 
nected with them, must be reserved for the 
future, when I shall report upon work of the 
same kind now in progress on other forms, but 
not sufficiently advanced to warrant descrip- 
tion. The results of Tangl on the chick, how- 
ever, and of Farkas on the silkworm are highly ~ 
suggestive, for the specifie work of develop- 
ment (Entwicklungsarbeit) of the dry sub- 
stance (7. €., organic substance + ash) in the 
ease of the former is 3.8 kilogram calories 
and of the latter 3.1. In consideration of the 
fact that the errors of observation and an- 
alysis are concentrated on these end figures 
and embodied in them, the almost complete 
identity of the results for these widely di- 
vergent forms, 
Fundulus ..... 3.61 (organic substance) 
Chicken 3.8 (dry substance) 
Silkworm ..... 3.1 (dry substance) 
is a strong argument in favor of Tangl’s 
hypothesis expressed two years ago, namely, 
that the specific work of development (Ent- 
wicklungsarbeit) is not a function of phylo- 
genetic position, but the embryogenetie forma- 
tion of living substances widely divergent in 
organization seems to be connected with an 
equal expenditure of chemical energy. 
In conclusion, I wish to acknowledge with 
1Owing to the presence of sea salts in my ma- 
terial, I am unable at this time to calculate the 
corresponding value for the dry substance of Fun- 
dulus. Unless the ash diverges very widely from 
the expected, however, the specific work of devel- 
opment of 1 gr. of dry substance will be in the 
neighborhood of the value given for the organic 
substance. 
