DEVELOPMENT OF DISTICHOPORA VIOLACEA. 157 



65. ZiEGLEK, H. E. — " Der biologische Bedeutung der amitotische Kern- 

 theilung im Thierreicb," ' Biol. Centralbl./ xi, 12 and 13, pp. 372— 

 389. Trausl. in 'Ann. N. H.,' viii, p. 362. 



DESCRIPTION OF PLATE 9, 



Illustrating Dr. Sydney J. Hickson^s paper on the 

 " Development of Distichopora/' 



Fig. 1. — Young ovum of Distichopora, situated in the cup-shaped tropho- 

 disc itr.). The germinal vesicle, 0, v., is situated near the centre of the 

 ovum. 



Fig. 2.— Germinal vesicle of the same stage, showing the vacuoles in the 

 nucleolus. 



Fig. 3. — Germinal vesicle of the ovum of Distichopora, migrating from the 

 centre to the periphery. The membrana limitans becomes obscure over the 

 pseudopodial processes. 



Fig. 4. — A peculiar condition of the germinal vesicle, observed in only one 

 preparation. 



Fig. 5. — A germinal vesicle, with chromatin granules arranged in a row. 



Fig. 6. — Germinal vesicle, containing numerous minute chromatin granules 

 situated at the periphery of the ovum. 



Fig. 7. — A stage showing the disappearance of the inner part of the mem- 

 brana limitans. 



Fig. 8. — A stage showing the complete disappearance of the membrana 

 limitans. 



Fig. 9.— Section of a young embryo which shows only two large nodes of 

 protoplasm, each of them containing a few deeply staining granules. The 

 yolk is omitted from the lower part of the section in order to show the loose 

 protoplasmic mesh-work which pervades the embryo. 



Fig. 10. — A later stage in the development, showing several nodes of 

 various sizes, some with nuclei, some without. 



Fig. 11. — A stage in the development corresponding to that of Fig. 10, to 

 show the relation of the nuclei to the yolk. Each nucleus is situated in 

 a small protoplasmic area or node, and the yolk granules close to it are ex- 

 tremely small. 



Fig. 12. — The same stage as Fig. 10, showing the different phases in the 

 formation of the nuclei. The details of the yolk are omitted. 



VOL. 35, PART 1. — NEW SEE. M 



