ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
41 
and there is only a small blastopore, the embryo has tlio form of a delicate 
line which extends from the blastopore along half a meridian of the egg. 
As Kuppfer and some later observers have noticed, tho vitelline pole is 
not placed exactly at the pole opposite to the germinal pole, but is to 
the side of the vertical axis of the egg. 
So far as concerns the time of appearance of the different organs 
Leuciscus does not agree with the Salmonidj©, which are generally taken 
as the type of development of Bony Fishes. 
Karyokinetic Phenomena in Cells of Blastoderm of Teleosteans.* 
— MM. E. Bataillon and R. Koehler find that sections, stained with 
boracic methylene-blue, of eggs eight days after fertilization present fine 
karyokinetic figures ; the chromatin always exhibits marked selection of 
this stain ; if eosin be used after the methylene-blue the nuclear 
granulations in a state of repose will be found stained by it. From 
these observations the authors conclude that, in these conditions, 
methylene-blue is a true reagent for chromatin in movement, and that, 
with the exception of the nucleoli, the granulations of the nucleus which 
are in repose have not the same reaction as the chromatin in division ; 
they must, therefore, change their chemical composition when they enter 
into the constitution of the filament. 
In the early stages of development of Leuciscus jaculus the blastodermic 
cells do not exhibit any individualized chromatin, and the karyokinetic 
figures are exclusively formed of achromatic elements. This important 
fact supports the opinion based on the most recent researches that, in 
the cell, the essential role does not belong to the chromatin, as has been 
hitherto supposed, but to the centrosomes. Chromatin exists at first in 
a diffused state in the protoplasm, as several authorities have already 
asserted. It is differentiated and individualized in this protoplasm in 
the form of colourable granulations ; and afterwards it becomes in- 
corporated with the nuclei to form the equatorial plates which are absent 
from the first stages. 
Vertebral Column of Eishes.f — Dr. H. Klaatsch finds around the 
notochord of dogfish embryos a double sheath, an inner, thicker layer, 
and a thin outer refractive membrane. This ontogenetic stage repre- 
sents, as Schneider recognized, the permanent state of Cyclostoma and 
of the cartilaginous Ganoids. The inner perichordal membrane is the 
notochordal sheath, a secretory product of the peripheral notochord cells ; 
the outer represents the elastica, probably due to perichordal tissue. 
The common ancestral type of all living fishes had around a cellular 
notochord a non-cellular fibrillar sheath, and outside this a strong elastic 
membrane. There is no reason to refrain from collating the vertebral 
arches of Amphioxus with those of Craniota. There is a fundamental 
similarity throughout ; in the primitive fishes cuticular fibrillar arches 
arose similar to those in Amphioxus ; “ in the inheritance of the posses- 
sion of these arches we see the reason for the marked differentiation of 
the skeletoblastic sheath in all fishes.” As primitive possessions the 
author also claims the longitudinal dorsal ligaments and the ventral liga- 
ment. But we cannot do more than indicate the lines along wjfich Herr 
* Comptes Rendus, cxvii. (1893) pp. 521-4. 
t Morphol. Jahrb., xix. (1893) pp. 649-80 (1 pi., 1 fig.). 
