EXPLANATION OF PLATE Jill.— Continued. 



Pigs. 10 — 16. — Represent the successive modifications undergone by the 

 germinal vesicle of the same Qg^, as they were produced under my eyes. 



Fia. 10. — Beside the nucleolus are seen pseudo-nucleoli suspended in a 

 mass of gi'anular matter (nucleoplasma). 



Fig. 11. — The pseudo-nucleoli have disappeared. The nucleolus is divided 

 into a large number of fragments, which rapidly disperse and spread through 

 the whole extent of .the germinal vesicle, as seen in figs. 12 and 13. The 

 gradual diminution in the refractive power of the nucleolar substance is also 

 noticeable. 



Fig. 14. — The central part of the nucleolus alone remains visible. 



Fig. 15. — All trace of nucleolus has disappeared. 



Fig. 16. — The membrane is ruptured and the contents of the vesicle escape. 



Figs. 17, 18, 19. — Three successive phases of the disappearance of the 

 germinal substance. These modifications were produced in the space of 

 twelve minutes. 



Figs. 20, 21. — Dicyema Elidones. 



The two figures represent the nucleus of the central cell of the body of 

 Dicyema Slidones. Kolliker and Wagner, regarding the body of these organ- 

 isms as hollow, have called the supposed central cavity of the body by the 

 name of Leibeshohle. 



According to my observations, which have reference both to the organization 

 and the development of Dicyema, there is no general body-cavity. The axis 

 of the cylindrical body is occupied by an immense cell, which extends from the 

 cephalic to the caudal extremity of the organism. In this cell, which is 

 filled with clear hyaline contents and traversed by a protoplasmic network, 

 the germs originate and embryos develop. It is the nucleus of this cell 

 that I have figured. 



Fig. 20. — Shows the nucleus seen in section. The nucleus is limited by a 

 thick membrane. It is filled with a clear homogeneous, colourless and trans- 

 parent substance ; it is traversed by bands of nucleoplastic matter. On the 

 left is the nucleolus formed of a thin peripheral layer and a large vacuole. 

 Near the superior pole of the nucleus are seen large granulations (pseudo- 

 nucleoli ?). 



Fig. 21. — Represents the same nucleus viewed from above, to show the 

 nucleoplastic network extended under the nuclear membrane. (Hartnack's 

 No. 10 immersion.) 



Plate XIV illustrates Mr. Sankey's Memoir on a New 

 Process for Examining the Structure of the Brain, and 

 Plate XIX that of Dr. Carpenter on the genus 

 Astrorhiza of Sandahl. 



