618 



BULLETIN OF THE 



LETTEES. 



The following letters are used throughout to designate respectively : — 



A = Amphiaster. 

 A^ = First arcliiamphiaster. 

 A^ = Second archiamphiaster. 

 A^ ■= Amphiaster of first segmenta- 

 tion sphere. 

 a = Aster. 



aa = Central area of aster. 

 ««/ = Structures at the centre of aa. 

 ae == External aster. 

 ai = Internal aster. 

 ar = Rays of aster. 

 ar' =*Thickenings in ar. 

 ars = Spiral astei'-rays. 



F. f2Jn 

 fpnl 



M. ma 



Tnpn 

 mpnl 



Female pronucleus. 

 : Female pronucleolus. 



Male aster. 

 Male pronucleus. 

 Male pronucleolus. 



N. n = Nucleus. 



T. p == Pedicel, or neck of polar 



globule. 

 pn, pn' = Pronuclei. 

 pnl = Pronucleoli. 

 pp = Pedicel-plate (Zellplatte ?). 



Fv = 



pz = 



R. r = 



r! = 

 r" = 

 rn = 

 ml = 



S. sp = 

 sp^ = 



sp^ 

 sp 



3 -— 



spf = 

 spfi == 

 spf" = 



spl = 



spm = 



spz = 



Purkinjean vesicle. 

 Clear zone in the yolk. 



Polar globule (Richtungs- 



blasclien). 

 First polar globule. 

 Second polar globule. 

 Nuclear structure of r. 

 Nucleolar structure of r. 



Nuclear spindle. 



First maturation spindle. 



Second maturation spindle. 



Spindle of first segmentation 

 sphere. 



Spindle fibres. 



Interzonal filaments. 



Thickenings in spf^ (Zell- 

 platte ?). 



Lateral zones of spindle 

 thickenings. 



Median (equatorial) zone of 

 spindle thickenings. 



Spermatozoa. 



V. r =Vitellus. 



ve = Vitelline envelope. 

 vm = Vitelline membrane. 



% 



TREATMENT, ETC. 



All Figures, except 62% 94, and 95, were drawn with the aid of the Chevalier- 

 Oberhauser camera ; and all, except 80'', 80", and 95, relate to Limax campestris. 



Figures 1-21, 27, 49, 51, 62% 65, 70% are magnified 140 diameters ; Figs. 30- 

 38, 76, about 200 diameters ; Fig. 95, 300 diameters ; all other Figures 750 

 diameters. 



The following Figures were made from living eggs : 1-21, 27, 30-38, 49, 51, 

 62% 65, 70% and 95. 



Figures 28, 29, 44, 52, and 52% are from sections of eggs hardened in chromic 

 acid ; all others, except Figs. 26 and 76, from the egg entire. 



Osmic acid (1%), followed by carmine, was employed to harden and stain those from 

 which Figs. 63, 64, 68-70, 71, 72, 75, and 77, were drawn. Those of Figs. 69 and 

 75 remained unstained by Beale's carmine. 



All eggs not otherwise specified were treated with acetic acid (l%-2%) for three 

 hours or more, and were subsequently stained in Beale's carmine. 



