NO. 1431. BREEDING HABITS AND EGG OF PIPEFISII-G VDGER. 



499 



Fig. 55. 



Plate IX. 



Divided thick-ended 32 to 64-celled type of blastoderm. The spUt is here a 

 narrow vertical cleft. Cell walls are pushing into the hasal layer which 

 has large vacuoles. 



56. Stage of 64 cells. Section through a normal or gently arche.l type. One 



cell not yet free from central periblast. ^ 



57. Stage of 64 cells. Type with flat surface and aV)rupt edges. In uclei are very 



large and in spireme stage. ., , ^ , 



58 Same stage. High-arched type. Cells still connected to periblast layer. 

 59^ Section through thick-ended blastoderm of 64-celled stage. No distinct cen- 



tral periblast. . . . ,. ^ 



60. Stage of 128 surface cells. Normal type with 7 cells m process of formation 



from basal layer of protoplasm. 

 61 Second type of 128-celle<l stage. Central periblast laden with yolk. 

 62" High-arched type of this stage. Mitotic spindles stand at all angles to each 



other, and vacuoles aid in cutting out the cell to right. 



63 Fourth type of 128-celled stage. Cells are being cut out ot the basal syncy- 

 ■ tium, the -Rand- is separated from the outer periblast by a sharp re-en- 

 trant angle. Many of the darkly stained nuclei have beside them solidly 

 stained bodies of unknown function. 



64 A section through another thick-ende.l blastoderm of this stage. There is 



no central periblast; cells have been cut out of the syncytium 



65 Normal tvpe of 256-celled stage. The nuclei all stain solidly, cells are being 



cutoff from the periblast, the "AW/" is nucleated. This is the earliest 

 stage with nuclei in central periblast. , , „ , 



66. Stage of 256 surface cells, second type. -Ramr sharply marke.l off trom 



the outer periblast. ■ ^u i ,coi 



67. Same stage, third type, showing cells in process of formation in the basal 



svncytium. _ 



Plate X. 



68. High-arched type of this stage, with solidly stained nuclei-periblast wholly 



free from cells. .i i. f .k;^i, fl.r 



69. Horizontal section through blastoderm of same stage as that ot ^^hIch fig. 



68 is a vertical section. 



70 Vertical section through blastoderm intermediate between figs. *^''>/indb7 



7i: Stage of 512 surface cells, normal type. Surface cells show a notable elon- 

 gation, some forming "bridges." . ,u^,„,^i^; 



72. Hfgh-arched type of this stage. The cells are of unequal sizes, the nuclei 

 stain solidly, the periblast is nucleate.l and in process of budding off cells. 



73 Same stage, flat-topped, abrupt-edged type. The "i^«»rf" is ot peculiar 



tin mass while on the right a whole spindle is shown. 

 74. 512-celled stage, fourth type. -Rand- and thick perib ast nucleated. 



Some cells with mitotic figures, but most nuclei stam solidly. 

 75 Stage of 1,024 cells on surface, normal type. Outer cells flattening to form 

 "- an epid;rmic stratum which is at places two-layered. Many nudei and 



vacuoles are found in the periblast, out ot which a number of cells are 



76. SamTstage; second tyge. The periblast is sunken in ^^e yolk, ^^ th« 



blastonu^res only sparingly fill the segmentation cavity thus enlarged. 

 The nuclei are in the spireme stage and a - Declschicht is preserit. 



77. High-arched type of this stage. The thick periblast is vacuolated and has 



a giant spindle at the left 



