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1891.] Embryology. 1021 
thoroughly to have ‘been covered by previous writers, and the author ; 
“attempts to show in the fairest manner possible which of the (always) 
several accounts is the more probable from his “observations on the bass,” 
We may now pass critically over the different sections of the paper. 
The egg of the sea bass is a small pelagic egg, about one mm. in 
diameter. Imbedded in the yolk, but near the surface, is a single 
large oil globule, which is always uppermost in the floating egg. After 
fertilization the protoplasm, which heretofore formed a thin layer over 
the egg, begins to flow to the pole opposite to the oil globule (lower), 
This patch of protoplasm at the lower pole is at first circular. 
before or during the first act of cleavage there arises an inequality in 
the axes, so that by the time the first two blastomeres are marked off the 
germ is bilateral. In the bass and mackerel the first two blastomeres 
are of equal size. ‘‘ This is normally so with the cod as well ; but on 
one occasion I observed that in all the eggs got from a single codfish 
the first two blastomeres were unequal in size. The inequality was 
very marked ; but the eggs were healthy and the average percentage of 
fish was hatched out.’’ 
This observation, which the author does not further follow up, must 
have an important bearing on the relationship of the first cleavage 
furrow to the plane of the adult body, and hence on the problem of the 
quantitative relationships of protoplasm (and nucleus?) in cell divi- 
sion. The somewhat hasty generalization, that in the Triploblastica 
the first cleavage plane divided the egg into right and left halves with 
reference to the adult, is meeting with general and inexplicable excep- 
tions ; and it is the exceptions determined by.casual observation as the 
above that show clearly that we do not yet understand the relationship 
between egg cleavage and adult structures. 
‘ The teleostean segmentation [cleavage of the egg] has eet 
been derived from a total segmentation essentially like that of Am 
bia ; and convinced of this, Rauber, Agassiz and Whitman, and Zieg- 
ler have endeavored to homologize the early furrows in the two groups. 
In regard to the first two furrows there can no be difference of opinion. 
The homology of the third teleostean furrow is by no means so clear. 
Ziegler, without entering into a detailed discussion of the matter, regards 
the first three furrows in the two groups as homologous. Agassiz and 
Whitman, after a critical examination of Rauber’s views, also pronounce 
-~ in favor of this homology, deciding that the third teleostean furrow rep- 
resents the equatorial furrow of Amphibia. I do not find, however, their 
reasons sufficient for discarding the homology offered by Rauber, sup- 
_ Ported as it is by variations (atavistic) in the teleostean germ toward 



