Fig. 45. 
Fig. 46. 
Fig. 47. 
Fig. 48. 
Fig. 49. 
Fig. 50. 
Boyer. — Mesoderm in Teleosts, 
PLATE VII. 
Drawings on this plate are transverse sections from an embryo of 96 hours, but 
somewhat more advanced than the one represented in Plate VI. Perenyi’s fluid. 
Kleinenberg's hamatoxylin. Sections 74 a thick. 
Through the region of the marginal vein (vn. marg.) in front of the pec- 
toral plate on the right side. The marginal vein in front of the first 
protovertebra runs obliquely (see this region in Fig. 56) ; hence in sec- 
tions successively nearer the tail it is seen farther from the axis of the 
embryo. X 310. 
Through the pectoral plate in the region of the nephrostome (pr’nph.). 
At this stage the lateral-line organ (o. In. l.) extends backward through 
a portion of the pectoral region (compare Figs. 46 and 42); this is 
not the case in a stage slightly less advanced. ‘The proximal region 
of the pectoral plate stands in close histological connection with the 
elements in the ventral region of the protovertebrs. X 910. 
Through the pectoral plate in the region immediately in front of the 
nephrostome. A few closely arranged nuclei below the protovertebra 
are from the anterior wall of the nephrostome (pr’nph.). The next 
section back shows the nephrostome, which is similar to that of Fig. 
46. X 310. 
Through the pectoral plate back of the nephrostome, showing the ele- 
ments (prf. my'tm.) passing over from the myotome into the pectoral 
plate. The proliferation of cells takes place both from the ventral 
margin of the myotome and from the peripheral layer, or muscle- 
plate (/a. mu.). X 750. 
Through the pectoral region at the fourth section back of the one repre- 
sented in Fig. 47. Nuclei (pr’f my’tm.) are shown, which undoubt- 
edly originate in the myotome, undergo rapid division, and later con- 
stitute a part of the pectoral plate (la. pet.). X 580. 
Through the pectoral region, at the next section back of that represented 
in Fig. 49. x 530. (Compare the relation between the pectoral plate 
(la. pet.) and the migratory cells (pr’f. my’tm.) of Figs. 49 and 50.) 
