ON FECUNDATION, MATURATION, AND FERTILISATION. 329 
5. Junin, C.—“ Structure et développement des glandes sexuelles ; ovogénése, 
spermatogénése et fécondation chez Styelopsis grossularia,” 
‘Bull. Se. de la France et de la Belgique,’ t. xxxv, 1893. 
6. Ruckert, J.— Die Chromatin reduktion bei der Reifung der Sexual- 
zellen,” ‘Ergeb. der Anat. u. Entw.,’? Merkel and Bonnet, Band iii, 
1893. 
7. STRASBURGER, E.—‘ Zellbildung und Zelltheilung.’ 
8. Vesporrsky, F.—‘‘ Entwickelungsgeschichtliche Untersuchungen,” Heft 
1, ‘Reifung, Befruchtung, und Furchung des Rhynchelmis-Lies,’ 
Prag., 1888. 
9. WuereteR, W. M.—‘ The Behaviour of the Centrosomes in the Fertilised 
Egg of Myzostoma glabrum,” ‘Journal of Morphol.,’ vol. x, 1. 
10. Witsoy, E. B., and Marruews, A. P.—‘‘ Maturation, Fertilisation, and 
Polarity in the Echinoderm Egg,” ‘Journal of Morphology,’ vol. x, 
No. 1. 
DESCRIPTION OF PLATE 17, 
Illustrating Mr. M. D. Hill’s “‘ Notes on the Fecundation of 
the Egg of Spherechinus granularis, and on the 
Maturation and Fertilisation of the Egg of Phallusia 
mammillata.” 
cent. Centrosome. chr. Chromosomes. f. prox. Female pronucleus. 
m. pron. Male pronucleus. 1st p. 6. First polar body. 2d p. b. Second 
polar body. Sp. ast. Sperm astrosphere. Sp. 2. Sperm head. Sp. cent. Sperm 
centrosome. sé sey. sp. First segmentation. 1s¢ seg. x. First segmentation 
nucleus. m.p. Middle piece. 1s¢ p. s. First polar spindle. 2xd p. s. Second 
polar spindle. 
Figs. 1—6.—Cross sections of eggs of Spherechinus granularis, 
Fig. 1. Section of unfertilised egg. 
Fig. 2. Section of egg ten minutes after fertilisation. 
Fig. 3. Section of egg fifteen minutes after fertilisation. Sperm astro- 
sphere has grown in size, and the centrosome is apparent. 
Fig. 4. Section of egg twenty minutes after fertilisation. Sperm astro- 
sphere is in contact with female pronucleus. 
es 
