320 



THE CAT. 



[chap. X. 



membranes coexist is the germ area, or gastrodisc. In the central 

 portion of this, a third membrane soon makes its appearance (Fig. 



144), This is the mcsohlad, 

 and is thought to be derived 

 from the h}7)oblast,''" by sub- 

 divisions of the cells of the 

 letter. The three-layered part 

 of the gastrodisc is a much 

 thickened part of it, and is 

 called the embryonal area, for it 

 is here that the embryo arises. 

 Tip to this point the matter 

 which is eventually to become 

 the body of a cat shows no re- 

 semblance to any animal what- 

 ever. It is but an aggregation 

 of cells of protoplasm arranged 

 as just described, and is rather 

 comparable with some very 

 lowlyorganisedfungus-like plant 

 than with anything we ordi- 

 narily understand as an animal. 

 § 5. It is in the midst of the embryonal area that the first sign 

 of the cat which is to be, is made manifest by the first appearance 



Fig. 142. — Longitudinal Section through the 

 Axis OF the Ovum, in which the Epiblastic 

 Cells (c) have almost surrounded the 

 Hypobla-stic ones ((')• 



il. Central cell. 



0. HypoWastic cell, occupying the interspace 

 left at one point by the epiblastic cells. 



FiK. 14n. 



A. Commencing separation between the epi- 

 blastic anil hypoblii.stic cells. 

 e. EpiWast. 

 i. HyiKiMast. 

 Ic. Cavity f'lpniicil by the separation. 



B. Comi>letion of the process, and formation of 

 a {reriu area, ov >;astro-ilisc, of two layers — 

 one (f) (if epiblastic cells, tlie other (i) of 

 hypiihlastic cells. 



OF THE EMiniYo. The first indication of the embryo is the appear- 

 ance of a longitudinal depression or furrow, termed the mednUary 

 (jroore (Fig. 145), and it is the sign of the appearance of the most 

 important and central of all the organs of the future animal, for in 



* In a papor read before tlio Eoyal 

 Society on March 23, 1876, Mr. E. A. 

 Scliiifcr describes tlie forinatiou of a 

 membrane in the cat's ovum between 

 the epiblast and liypoblast. This mem- 

 branous follicle he named, mcmhrana 



Umitaiis TiypohlaMica. The fact of its 

 ]»rescuco favours the view according to 

 which the mesoblast is derived from the 

 epibla.st. See Tro. Koy. Soc, vol xxiv., 

 plate 10. 



