294 



DR. J. B. GATENBY ON THE GERM-CELLS AND 



10. Maas, 0. — " Ueber Reifung und Befruchtung bei Spongien." Anat. 



Anz., Btl. xvi., 1900. 



11. MacBride, E. W.— " Text-Book of Embryology, Part I." Macmillan, 



London, 1914. 



12. Morgan, T. H. — 'Regeneration.' Macmillan Company, N.Y., 1901. 



13. Robinson, M. — "The Division of the Collar-Cells of the Calcarea 



Heterocoela."' Quart. Journ. of Micro. Science, vol. lvii., 1920. 



14. G-atenby, J. Bronte. — " The Gametogenesis and Early Development of 



Limnaa stagnalis, etc." Quart. Journ. of Micro. Science, vol. lxiii., 

 1919. 



DESCRIPTION OF THE PLATES. 



Explanation of Lettering. 



3= stages in passage 

 into mesoglea. 



of collar-cell 



AC = 

 AS= 

 £M= 



C = 

 COL= 

 ECT = 



END = 

 FC = 



EL = 

 FPN = 



GA = 

 GAO= 

 GAM= 



GC = 



GCAV= 



GCX= 



GE = 

 GX= 



1T= 

 LGC = 



M = 

 M&NG = 



MAM = 



acrosome. 



archoplasmic sphere. 



basement - membrane of collar 



epithelium. 

 :centrosome. 

 collar of collar-cell, 

 ectoplasmic zone of oocyte or 



egg- 

 :encloplasmic zone of oocyte, 

 future histocytes or collar-cells 



of larva, 

 flagellum. 

 female pronucleus. 

 Golgi apparatus. 

 Golgi apparatus of oocyte, 

 granular (mitochondria) amoebo- 



cyte. 

 granular cells of larva, 

 gastral cavity of sponge, 

 future granular (and lower cells?) 



of larva, 

 gastral or collar-cell epithelium, 

 large granules possibly of Golgi 



nature, 

 inner thickening of collar, 

 lower granular cells of larva, as 



distinguished from inner granu- 

 lar cells, 

 mitochondrium. 



mitochondria and nutrient (yolk) 



granules, 

 macromitosome (" Nebenkern ") 



or middle -piece of sperm. 



With regard to fixation and staining, the 

 F.W.A.= Flemming's fluid without acetic acid 



MES = mesogleal cells. 

 MPN = male pronucleus. 



N = nucleus. 

 NCH=nucleus of collar-cell (choano- 

 cyte). 

 NK = drawn-out "neck " of collar-cell 



formed of hyaline protoplasm. 

 NSC = nurse-cells associated with sper- 

 matogenesis. 

 OG = outer granules of flagellated cell 

 (possibly yolk of sorne'sort). 

 OGA = oogonium (young oocyte) formed 

 in situ from collar-cell. 

 OT = outer thickening of collar. 

 OTE = oocyte. 

 PB = polar body. 

 PC = first stages of metamorphosis of 



collar-cell into germ-cell. 

 PE= thickening of protoplasm on peri- 

 phery of collar-cell, inside the 

 collar. 

 S = sperm. 

 SCO = sperm-carrying cell (metamor- 

 phosed collar-cell). 

 SN = sperm-nucleus. 



SPA=space around, forming spermato- 

 zoa or nurse-cavity. 



SPT = spermatids. 



VAC = vacuolated region of cytoplasm 

 caused by entry of sperm and 

 flow of material to the region 

 of entry. 

 ;r=supposed remains of macromito- 

 some (MAM). 

 Y = yolk-sphere or nutrient meta- 

 plasmic granule. 



following abbreviations have been used : — 

 i II. W, A. = Hermann's fluid without acetic 



