ON THE EMBRYOLOGY OF THE TELEOSTS. 



211 



Explanation of Plates. 



Fig. 1. Micropyle of egg-of Ctenolabrus in section. 



Fig. 2. Surface view of same with surrounding pore canals. 



Fig. 3. Merlucius the germinal disc above showing the archamphiaster of maturation. 



Fig. 4. Early egg of Ctenolabrus before maturation and impregnation. 



Fig. 5. Portion of germinal area of egg of Merlucius with probable polar globules. 



Fig. 6. Formation of polar globule and expulsion of same through the micropyle. 



Fig. 7. The same a few seconds later ; in these two figures the details of micropyle are omitted. 



Fig. 8. A polar globule attached to one cell of a blastoderm of two segments. 



Fig. 9-10-11. Three successive steps in the formation of the biscuit-like germinal area, shown in section, 

 the shaded portion extending out from that region forming a portion of the intermediary layer. 



Fig. 1-. Result of first segmentation, the "tails" on either side the rudimentary " bourrelet peri- 

 pherique." 



Fig. 13. Preparations for second segmentation. 



Fig. 14. Resulting four segments with the temporary furrows of the yolk. 



Fig. 15. Diagram of amoeboid motions in blastoderm of eight cells. 



Fig. 16. Blastoderm of eight cells showing a common irregularity. 



Fig. 17. Amoeboid appearance of two cells. 



Fig. 18. Preparation for dividing from eight to sixteen cells, showing irregularity in time of division. 



Fig- 19- Blastoderm of 16 cells. 



Fig. 20. Blastoderm of 24 cells. 



Fig. 21. Optical section through the edge of a blastoderm in a late stage of segmentation. 



Fig. 22. Beginning, and fig. 23, later stage of invagination of hypoblast. The upper shaded portion 

 representing the epiblast and lower layer cells; s, the segmentation cavity, and the dark narrow line just 

 beneath, the intermediary layer; the broad shaded portion shows the outline of the lateral invagination. 

 The black line beneath h, the hypoblast, and e. a., embryonic area is possibly the segmentation cavity of 

 Ryder. 



Fig. 24. Blastoderm of fig. 23 from above, showing the outline of the segmentation cavity, the line across 

 shows the plane of the preceding section. 



PLATE XV. 



Fig. 24*. Cells from the margin of blastoderm ; and beneath, free cell formation in peripheral cushion ; 

 amphiaster x, and an aster b, are shown and also a stage in the formation of cell walls. 



