Bauhaus-Universität Weimar

Titel:
Dictionary of philosophy and psychology including many of the principal conceptions of ethics, logics, aesthetics ... and giving a terminology in English, French, German and Italian, vol. 1 [a-laws]
Person:
Baldwin, James Mark
PURL:
https://digitalesammlungen.uni-weimar.de/viewer/image/lit29445/145/
BLASTOCOELE — BLIND SPOT 
if done with intent to corrupt public morals, 
to mock and insult believers, or to bring 
religion into hatred or contempt. See The 
Mod. Rev. (1883), 586 ff., and Blackstone, 
Comm., iv. 59. (k.m.w.) 
Blastocoele [Gr. ßXaaröf, germ, + koIXos, 
hollow] : Ger. Dotterhöhle, Furchungshöhle ; 
Fr. hlastocèle; Ital.hlastocele. A cavity which, 
in the development of many animals, forms in 
the midst of the group of cells produced by the 
cleavage of the ovum. 
A term suggested by Huxley for the seg¬ 
mentation cavity of von Baer. It gives origin, 
in some cases, to the enteron or digestive cavity 
of the coelenterates, and is regarded on the 
Planula Theoky (q. v.) as the primitive gut. 
Where the enteron arises by invagination it 
must be carefully distinguished from the blasto¬ 
coele. See Embryo (with figure). (c.Ll.m.) 
Blastoderm [Gr. ßXaoro'r, germ, + déppa, 
skin] : Ger. Keimhaut, Blastoderm ; Fr. blasto¬ 
derme] Ital. blastoderma. The layer of cells 
overlying the yolk, forming the germinal 
membrane from which the embryo animal is 
developed. (c.Ll.m.-e.s.g.) 
The term is due to Pander (1817), who 
observed the blastoderm of the fowl, and 
traced its differentiation into an outer or 
serous layer, a middle or vascular layer, and 
an inner or mucous layer. Bemak (1850-5) 
showed that the middle layer splits or cleaves 
into two. Thus four layers result, the relations 
of which have been in the light of more recent 
inquiry tabulated by Allen Thomson as 
follows :— 
Primi¬ 
tive 
Blasto¬ 
derm 
( 
Ectoderm 
Epiblast 
Body wall 
(Somato- 
Mesoderm. 
Mesoblast : 
pleure) 
Secondary 
- Blasto¬ 
Endoderm - 
Hypoblast 
Visceral wall 
(Splanchno- 
derm 
pleure) j 
In holoblastic or complete segmentation the 
primitive blastoderm forms a continuous 
vesicle ; in meroblastic or incomplete seg¬ 
mentation it forms a layer resting upon the 
uncleaved or unsegmented yolk-mass. See 
Ovum, and Cleavage. 
Literature : F. M. Balfour, Compar. Em- 
bryol. (1880-81); Allen Thomson, art. 
Embryology, Encyc. Brit. (9th ed.). (c.Ll.m.) 
Elastomere [Gr. ßXaarck, germ, -f- pépos, 
part]: Ger. Furchungskugel] Fr.blastomère] 
Ital. blastomero. Any one of the cells produced 
by the cleavage of the animal ovum. See 
Embryo. (c.Ll.m.) 
Blastopore [Gr. ßXacnös, germ, -f- 1rôpos, 
passage]: Ger. Cfrmund] Fr. blastopore] Ital. 
blastoporo. The orifice of the two-layered 
invaginate embryo or gastrula of many 
animals. 
The term was introduced by Lankester in 
1875. Regarded by Haeckel as the primitive 
mouth, and yet considered by many as the 
homologue of the anus of Piusconi in the frog, 
this opening has been the subject of much dis¬ 
cussion by zoologists. The term blastopore, as 
descriptive, avoids theoretical implications 
as to its ultimate fate. It seems, in some 
cases, to mark the jiosition of the future mouth ; 
in others of the future anus; and in some, 
by becoming slit-like and closing along the 
middle line, of both. Bee Embryo (with 
figure). 
Literature : E. B. Lankester, Quart. J, 
Microsc. Sei., xv. (1875) 163; Minot, Em¬ 
bryology. For its relations to the primitive 
streak in vertebrates, see Balfour, Compar. 
Embryol. ; also Hertwig, Embryol. of Verte¬ 
brates (Man and Mammals). (c.Ll.m.) 
Blastosphere [Gr. ßXaarös, germ, + erfydipa, 
sphere]: Ger. Blastula ; Fr. blastosphere ; 
Ital. blastosfero. The spherical mass of cells 
enclosing the blastocoele, the product of the 
holoblastic segmentation or cleavage of the 
ovum. See Embryo. (c.Ll.m.) 
Blastula [Gr. ß\acTT
    

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