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Miscellaneous. 251 
On the first Formation of the Body in the Vertebrata. 
By Professor Hts. 
Professor His, in continuing his researches upon the ovular de- 
yelopment of the Vertebrata, has arrived at some results fitted to 
produce a considerable change in the theory of blastodermic la- 
mellze as modified by Remak. According to the author, the blas- 
todermic lamelle would seem to constitute only secondary forma- 
tions, and even the median lamella cannot at any period be regarded 
as an anatomical whole. 
M. His distinguishes, from the first, in the hen’s egg submitted 
to incubation, two primitive blastodermic formations: at the ex- 
pense of one are formed all the organs closely or distantly related 
to the nervous system—the central nervous system, the peripheral 
nerves, the epidermis, the glands, and the muscles, both striped and 
smooth ; from the other originate the blood and the connective 
tissues. The former is what is generally denominated the proli- 
gerous disk ; but M. His gives it the name of archiblast or neuroblast ; 
the latter is the white vitellus, or the parablast or hematoblast, ac- 
cording to M. His. 
The archiblast is derived from what Meckel von Hemsbach de- 
nominated the ovule properly so called—that is to say, the part of 
the egg which undergoes segmentation after fecundation. ‘The pa- 
rablast, on the contrary, is an adventitious formation, comparable 
to the cells of the granular tunic of the ovum in the Mammalia ; and 
its constituent elements are similar in both the fecundated and un- 
fecundated ovum. : 
In the fecundated but not incubated egg, M. His distinguishes 
the germinal disk and the white and yellow vitellii The white 
vitellus forms a thin stratum surrounding the yellow one, and is 
prolonged beneath the germinal disk in the form of a cord to the 
centre of the egg. The germinal disk is a thin plate which rests 
upon the white vitellus, in the place where the ovule, properly so 
called, occurs in the unfecundated egg. After fecundation, this 
ovule, by segmentation, becomes converted into the germinal disk. 
Beneath this there is a cavity filled with liquid, the bottom of which 
is formed by the white vitellus. The peripheral part alone of the 
germinal disk rests immediately upon the white vitellus. Their line 
of union is what M. His names the dblastodermic circumvallation 
(Keimwall). The part of the germinal disk beneath which the cavity 
is situated is the pellucid area; that which assists in forming the cir- 
cumvallation is the opaque area. The author reverts to the opinion 
of MM. Schwann and Reichert, according to which the elements of 
the white vitellus are true nucleated cells. The cells of the germi- 
nal disk form at first a continuous layer—the superior blastodermic 
lamella. From the inner surface of this lamella start cords which 
anastomose and form a sort of network, but never, before incuba- 
tion, produce the true inferior blastodermic lamella. 
The first result of fecundation is the complete formation of the 
