Figure 39. Warnek's drawings for his work on the development 

 of gastropodan molluscs (development of Lymnaeus 

 stagnalis) . 



3-5 — the division of the light spot in the fertilized 

 ovum; 



7 — at the external area, light spot coming near the 

 surface; a light crescent-shaped formation appears; the 

 beginning of the formation of elevation; 



the elevation acquires the form of a club-head; 



9 the second elevation begins to form; 



10 — the second vesicle separates; the light spot becomes 

 spherical; the crescent-shaped region disappears; 



19 — completely separated yolk globules; 



22— the beginning of secondary nearness of the yolk 

 globules ; between them a light space ; 



25— the greatest nearness of the yolk globules; the 

 nuclei are not seen; 



25a— no n- simultaneous division of nuclei into two primary 

 yolk globules; 



27— non-simultaneous division of yolk globules; 



28-30 — gradual distortion of first fissure of division; 



3 4 cross -shaped position of the globules of division; 



36a — no n- simultaneous division of the nucleus into four 

 yolk globules; 



40— globules of division of the fourth stage (la- Id) are 

 situated in the space between globules of the third stage 

 CIA- ID) ; 



43— extension of nuclei in the yolk globules of the 

 third stage (1A-1D) ; 



45— the yolk globules of the fifth stage (2a-2d) 

 separated from the globules of the third stage (2A-2D) 

 and situated between the latter; 



46a — adjacent situation of nuclei, showing the origin 

 of the yolk globules of the fifth stage from the globules of 

 the third stage; 



47 — the yolk globules of the sixth stage (la 2 -Id 2 ) 

 separated from globules of the fourth stage (la 2 -Id 2 ); 



50 — the ninth stage of division. 



549 



