3S8 
J. F. McClendon 
ning no yolk, fig. 4, and if all tliese are artefacts, the assertion that an 
alveolar structure in Butschli’s sense exists in the cytoplasin of the frog’s 
egg is not based on optical evidence (cf. Rhumbler). The fact remains 
that the spaces which Gurwitsch supposed to be filled with enchylemma 
in the centrifuged frog’s egg are in reality filled with fat droplets, and the 
process which he describes as a destruction of the alveolar structure is in 
reality an aggregation of the fat droplets. Wliether the process which 
Gurwitsch describes as a restitution of the alveolar structure, which 
occurs in eggs after they have been removed from the centrifuge, is a 
redistribution of the fat droplets, I cannot positively affirm, as I have 
not determined that the fat droplets are ever uniforraly redistributed, 
neither do Koxopacka’s figs. 12 and 14, PI. XXVI indicate such a process, 
and although on p. 772 she States that the vacuolated layer seen in cen- 
trifuged eggs disappears soon after the eggs are removed from the centri- 
fuge, she adds that the stratified arrangement of substances persists 
during the entire development of the eggs. 
On the Cause of the Abnormal Development of Centrifuged Eggs. 
Gurwitsch assunies that the abnormal development of centrifuged 
frog’s eggs is due to the failure of the nuclei to fit the portions of the cyto- 
plasm which surround them. This he attributes to the meniscus fcr- 
mation, which did not occur in my experiments. The question arises 
whether such an assumption is necessary to explain the facts. I con- 
cluded (09, 1) that the physical and Chemical differences between the 
layers of the egg were sufficient to account for the abnormal develop- 
ment, and found that if the centrifugal force was sufficiently prolonged 
(2771 X gravity for 20 minutes) not even the beginning of Segmentation 
ever occured. Gurwitsch maintains that similar explanations are in- 
validated by the fact that sometimes a portion of one layer Avill segment 
while the remainder of the layer is unsegmented, that is to say that the 
injury to the egg is independent of the stratification. It shoiüd be re- 
membered that frog's eggs are easily injured by handling, and that cen- 
trifugal force not only stratifies the egg, but causes currents in the egg 
and presses the eggs one against the other The currents in the egg are 
indicated by the Streaming of the black pigment observed by Morgax 
and myself. Pflüger observed that if the frog’s egg be inverted, the 
small cells appear in the white hemisphere, and Borx demonstrated this 
to be accompanied by an inversion of the egg contents. It has been pro- 
ved that the polarity of the frog’s egg is determined by the arrangement 
of egg substance, either deutoplasm or protoplasm proper. The nearly 
