20 
which extends beyond a plane passing through the equator of the egg, 
giving to the finely granular blastodisc a pear-shaped outline. Its 
significance is not as yet fully comprehended and nothing more than 
passing remark can be made until the later stages have been more 
carefully studied. 
A retrospect emphasizes the differences of opinion existing and 
leads us to ask and wonder if the cleavage of the egg of Lepidosteus 
shows such wide variations, now cleaving in a holoblastic fashion 
(BEARD), again following the meroblastic type (DEAN), then conforming 
to an intermediate type (the writer)? If this be true, how shall we 
interpret a cleavage so remarkable and exceptional, and what new 
light may it throw upon the problems of gastrulation and embryo 
formation? If it be false, wherein lies the explanation of these diverse 
statements ? 
It would seem advisable before concluding as to the character 
of the cleavage to point out certain possible sources of misinter- 
pretation. 
Although BALFouR and PARKER state that the segmentation is 
complete, I think all will agree that they nowhere adduce evidence 
to prove this assertion, moreover they repeatedly say the furrows 
‘nearly meet” and to the latter statement the illustrations conform. 
Brarp’s later writings affirm his former conclusions. The state- 
ment, however, that “all the eggs of the proper stage show 
either four or eight complete furrows reaching to the 
lower pole”, leaves in my mind a shadow of uncertainty. Even in 
those Ganoids (Acipenser and Amia) which are more typically holoblastic, 
one does not find this marked regularity. I accordingly believe BEARD’s 
observations need confirmation. 
Dr. DrEan’s observations on the early stages are more detailed 
than those of the previous writers, but unfortunately the descriptions 
and illustrations were made from material fixed in alcoholic picro- 
sulphuric. Were drawings made from my material fixed in either 
picro-sulphuric or picro-acetic, they would present striking similarities 
to those depicted by DEAN, but to consider these monstrosities as 
normal is a most serious misconception. Dr. DEAN apparently 
realized later the uncertainty of these surface views, since he states 
in his paper on Amia (p. 414) that he had an “opportunity to 
observe the living material, and to prepare the figures of those 
stages especially which in surface view (as my studies of Acipenser 
and Lepidosteus had taught) could not well be examined in the fixed 
material”, 
