Plate XXVI. 



Fig. 17. — Primary oocyte, showing tlie karyolciiiotic figure for tlie first 



])(ilar glolmle. x 2 inim. '/ij- 

 Fig. 18. — Section through the equatorial plane of the karyoldnetic fignre 



for the first polar gloLnle ; the egg was ])reserve(l witli sublimate 



solution (Winkel oc. 3. x oh. S). 

 Fig. 19. — After emission of two |)olar glolmles (Winkel oc. 3 x oJ). 8). 

 Fig. 20.- — »Section .showing one stage of fertilization, when the two pronuclei 



(m.n. ixw\ /.It.) stand side hy sid(\ x 2 inim. '/ij (Zeiss). 

 Fig. 21. — Median section of fertilized egg, in which is f »utid a karyokinetic 



figure for the first cleavage, x 2 imni. '/,.,. 

 Fig. 22. — Median section of a young morula, x 2 F. 

 Fig. 23. — Median section of a young morula, showing the blastoeœlic pore 



(bLc). X 2 F. 

 Fig. 24.— Median section of a young hlastula, in which one blastoderm cell 



is seen giving off plasmic corpuscle {pl.co.). x 2 F. 

 Fig. 25. — Median sagittal section of an advanced blastula ; two plasmic 



corpuscles are detected in tlie segmentation cavity, x 2 F. 

 Fig. 2() (a, Z^).— Sagittal sections of a highly developed blastula, in which 



the invagination has just begun ; a shows a median section, x 2 



imm. 7i2- 

 Fig. 27. — Median sagittal section of a gastrula in which the invagination 



is deeper, x 2 imm. 7i2' 

 Figs. 28 (u-f). — Three transverse sections of an advanced gastrula ; rt througli 



the central depression, h behind the central de]>ression, and c near 



the posterior end of the emliryo. x 2 F. 

 I'^ig. 29, — Median sagittal section of an embryo at nearly the same stage 



as ill Fig. 8. x 2 inun. y^.,. 

 I'igs. 30 (r;-r). — Transverse sections of an embi-yo at nc^arly tho same stage 



as the j^receding ; « shows a ])ortion (left) of a section tln-ough the 



blastopore, h just behind the blastopore and through the ventral groove 



{v.gr.), c near the posterior end. x 2 F, a with the tube drawn out. 

 Fig. 31. — Transverse section through the l)lastopore of a larva, in which tlie 



anterior diverticula [nni.<liv.) are well develo]ied. x 2 F. 



