EARLY DEVELOPMENT OF GRANTIA COMPRESSA. 293 



with these yolk-granules, but more towards the posterior or inner pole, a 

 number of mitochondria. At the outer or anterior pole of the cell lie a group 

 of special granules doubtfully identified as of true yolky nature. The nucleus 

 is small, extremely basophil, and contains a karyosome. Lying on the 

 nucleus is a distinctly marked capsular bod)', from which the flagelluin 

 arises ; this body is thought to be the Golgi apparatus (PI. 23. fig. 33). 



The large centrally situated "granular cells" (GC in PI. 23. figs. 28 and 32) 

 are formed of a nucleus which stains palely, and contains a coarse karyosome 

 and a cytoplasm in which lies a number of granules, some mitochondria, 

 others yolk, and certain others (GXin PI. 23. fig. 31) possibly Golgi apparatus. 

 In most cases these large granular cells contain fewer yolk-spheres than the 

 flagellated cells and about the same number of mitochondria. 



5. The smaller inner granular amceboid cells (or mesenchyme) are 

 apparently derived by an inward immigration from the flagellated cells, and 

 are distinguished by the fact that they are crammed with mitochondrial 

 granules and possess very little, if any, yolk. In Grantia eompressa the 

 amphiblastula, at the period drawn in PI. 23. fig. 28, generally contains only 

 two or three such cells (PI. 23. tig. 30). 



University College, London, 

 October 30, 1919. 



29. Bibliography. 



1. Conklin, E. G. — "The Orientation and Cell-Lineage of the Ascidian 



Egg." Journ. Acad. Philadelphia, vol. xiii., 1905. 



2. Dendy, A. — " G:mietogenesis of Grantia eompressa." Quart. Journ. 



of Micro. Science, vol. lx., 1915. 



3. " The Pseudo-gastrula Stage in the Development of Calcareous 



Sponges." Proceed. Roy. Soc. Victoria (Australia). 1898. 



4. Gatenby, J. Bronte\ — "The Modern Technique of Cytolog_y." Quart. 



Journ. of Micro. Science, no. 63, 1919. 



5. " The Identification of Intracellular Bodies." Journ. Royal Micr. 



Society, 1919. 



6. Gorich, W. — " Zur Kenntnis der Spermatogenese bei den Poriferen und 



Gqelenteraten nebst Bemerkungen liber die Ovogenese der Ersteren." 

 Zeit. f. wiss. Zool., Bd. lxxvi. 



7. Haf.CKEL, E. — " Ueber die sexuelle Fortpflanzung und das natiirliche 



System der Schwiimme." Jenaische Zeit. f. Med. u. Naturwiss., 

 Bd. vi. 



8. Hikschler, Jan. — " Ueber Plasmastrukturen in den Tunicaten-, Spon- 



gieh-, und Protozoenzellen." Anat. Anz. vol. xlvii., 1914-15. 

 8a. Jorgensen, Max. — " Beitrtige zur Kenntnis Eibildung Reifung, Be- 

 fruchtung, und Furchung bei Schwainmen (Syconen)." Arch, fur 

 Zellfor., Bd. iv., 1910. 



9. MlNCHlN, A. — Lankester's 'Treatise on Zoology/ Part II. 



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