Fig. 4. — A mature ovum, 100 times the natural size. The spheroidal egg cell is enclosed in a 

 thick structureless chorion (yc) ; a projecting micropyle (ym) opens at one point of it. The yolk is 

 composed of spheroidal, thickly compacted yolk grannies (yd) of equal size. The clear spheroidal 

 germinal vesicle (yn) contains a large dark germinal nucleus (yf), and this, again, a visible double 

 contoured germinal nucleolus (yp). 



Fig. 5. — A follicle of the ovary, seen from the inner (endoderrnal and abxial) surface, four times 

 the natural size. The ova are distributed on the free endoderrnal surface (turned to the coronal sinus) 

 of the fan-shaped transverse folds of the follicle in such a way that the smallest and younger ova 

 lie on the basal margin of insertion of the folds, but the larger and older on its freely projecting 



Fig. 6. — A follicle of the ovary in longitudinal section, four times the natural size. The flat axial 

 ectodermal surface of the subumbrella (qw) is separated by a thick gelatinous fulcral plate (zw) from 

 the thickly folded abaxial endoderm surface, from whose germinal epithelium (ds) the ova are 

 originated, h Umbrella cavity, cs Hollow cavity of the coronal sinus. 



Fig. 7. — Fold of a follicle of the ovary in longitudinal section, eight times the natural size. The 

 more mature ova (so) surrounded by a chorion, are enclosed in special fulcral capsules (yz), wide, 

 separate, gelatinous sheaths formed by a superficial abaxial growth of the supporting plate of the sub- 

 umbrella (wz). cs Hollow cavity of the coronal sinus. 



Fig. 8. — Horizontal transverse section through an interradial cathammal node, 300 times the 

 natural size, ug Gelatinous substance of the umbrella, transformed into fibrous cartilage (ug 2 ) at 

 the point of fusion. du 2 Umbral endoderrnal lamella of the cathamma. div 2 Subumbral endoderrnal 

 ^amella of the cathamma. zw Gelatinous supporting plate of the subumbral transformed into 

 fibrous cartilage (zw 2 ) at the point of fusion, cs Coronal sinus (in this case divided by the four septal 

 nodes into four perradial spaces), du Umbral endoderrnal epithelium ; die subumbral endoderrnal 

 epithelium of the coronal sinus. md" Insertion of the deltoid muscle (in transverse section). 

 mw Circular muscles of the subumbrella. quo Endoderrnal epithelium of the subumbrella. 



Fig. 9. — A small piece of fibrous cartilage from the hardened gelatinous tissue of the cathamma 

 (fig. 8, ug 2 ), 600 times the natural size. The histological structure of this modified gelatinous tissue 

 immediately at the point of fusion is similar to the fibrous cartilage of the vertebrata?. yz Cartila- 

 ginous cells enclosed in cartilaginous capsules, yi Fibrous cords of the intercellular substance. 



Fig. 10. — Horizontal transverse section through a fused clasp, 300 times the natural size. 

 qe Ectodermal epithelium of the exumbrella. qw Ectodermal epithelium of the subumbrella. 

 (In Umbral endoderrnal epithelium, dw Subumbral endoderrnal epithelium of the lobe pouch. 

 ug Gelatinous substance of the umbrella transformed in ug 2 into fibrous cartilage, zw Gelatinous 

 substance of the subumbrella transformed in zu\ 2 into fibrous cartilage, kl Cathamma lobare. hi Lobe 

 pouches. 



