THE EFFECTS OF HYrEKTONIO SOLUTIONS. 
477 
EXPLANATION OF PLATES 24-27. 
Illustrating Mr. J. Gray’s paper on ‘^The Effects of Hyper- 
tonic Solutions upon the Fertilised E ggs of Echinus. 
(Echinus esculent us and E. acutus.)” 
[Most of the outlines of the figures were drawn at talde level with a 
camera, under Zeiss ocular 2 and 2 mm. oil-immersion objective.] 
PLATE 24. 
Figs. 1-20. 
Figs. 1-.5.- — Nuclear figures of eggs of Echinus esculentus which 
had been treated with 50 c.c. sea-water -|- 5 c.c. 2t\ M. NaCl for half 
an lioni’. 
Fig. 1 . — Fused male and female pronuclei showing vesicle. 
Fig. 2. — Fused male and female pronuclei showing no vesicle, but a 
small dark mass of chromatin. 
Figs. 3 and 4. — Later stages of eggs in this series showing regular 
and irregular mitotic figures. [Magnification oc. 2, objective 
Fig. 5 . — Egg showing mnnerous sperm nuclei in process of division. 
[Magnification oc. 2, ol>jective L] 
Figs, fi-l 6.— Nuclear figures in eggs of E. esciilentus wdiich had 
been treated witli 50 c.c. sea-water + 6 c.c., 21 M. NaCl for half 
an hour. 
Figs, fia and fi b. — The female and male pronuclei from a single egg. 
Within the former are two vesicles, while in the latter are four minute 
bodies with a faint vesicular nature. 
Fig. 7. — Fusion of a large and small nucleus; the former contains 
thirty-six or more chromosomes, with one large and four small vesicles. 
The accessory male nucleus shows two small vesicles. 
Fig. 8. — This egg shows two accessoi-y male nuclei which have not 
fu-sed with the female pi’onucleus. Each show the typical haploid 
number of chromosomes and no vesicles. Within the larger nuclei are 
the full somatic number of chromosomes, together with a large, very 
darkly stained vesicle. 
Fig. 0. — Shows two large and two small vesicles within a nucleus 
whose chromosomes are well defined. 
