1885.] Embryology. 203 
During my observations on the development of Gadus, made 
in 1881, I noticed a space which exists between the skin and mus- 
cle-plates (see Pl. x, Figs. 43 and 44, Contrib. Embryog. of Osse- 
ous Fishes), since then Carlo Emery?! has published his observa- 
tions founded on a study of transverse sections of the tails ot 
aia ps 8 Nerapee sryyyee S. 
i GS a, $ an Par 
aa La T i ae Òr mg S> ) a A 
mn If aa 
Seale MM: mn 
a e e 
————_ a T a A es 
X: aal, 
ISAAA = 
Ep- ECS E SE Q 
pren RAE, 
EXPLANATION OF FIGURES. 
Portions of vertical transverse sections of the caudal fin of a salmon embryo, show- 
ing the development of the halves of the permanent rays of one side. 
Fic. 1.—¢f, deep and superficial layer of epiblast; #, mesoblast; c, center of meso- 
blastic tissue proliferated into the dermal tail fold; ff, filamentous embryonic 
fin rays cut transversely near the margin of the caudal fold. 
“‘ 2.—Froma section nearer the base of the fin to show the process of fusion of 
the primitive rays, gr. The other letters as before, - 
«« 3.—From a section in which the rudiment of the permanent ray, pr, is covered 
by mesoblast, the fil tous rays, #7, having been still more thickly envel- 
in Fig. 2 ra 
of the presence o amentous embryonic rays can be seen ‘in the sub- 
“ 4.—Froim a section through an outer caudal ray near its base, showing the fibers 
ff enveloped externally by the mesoblastic core of the permanent ray, which 
forms a swelling which is cut across, on the top of which the first traces of 
the proximal end of the permanent ray appears. 
s 5.—Section through the basal part of a median ray, the primitive fibers in the 
vicinity having nearly disappeared, the ray itself again becoming covered ex- 
ternally by proliferated mesoblast. All of the figures enlarged 365 times, the 
cells being shown only in the two last. 
embryos of Fierasfer, Belone and Lophius, in the early lophocer- 
cal stage. In these he finds a homogeneous secretion interpose 
between the muscle-plates and the epiblast, extending also into 
1Sulla existenza del cosidetto tessuto di secrezione nei vertebrati. Att, R. Accad. 
Sci., Torino, XVII, 1883. 
