LiNViLLE. — Maturation Pulmonates. 



PLATE 1. 



All Figures are of eggs of Limncea elodes. 



Fig. 1. First maturation spindle, telophase. Centrosomes of large size. Sperm- 

 head near vegetative pole. Breaking of membrane at animal pole acci- 

 dental ; the flattening of the egg normal. 



Fig. 2, First maturation spindle. Portions of the membrane of germinative vesi- 

 cle still visible. Form of deep aster of spindle modified by sperm-aster. 



Fig. 3. Deep centrosome and aster, to show the rays beginning at centrosome and 

 extending through and beyond the centrosphere. 



Fig. 4. First maturation spindle. The sixteen chromosomes (concealed tetrads) 

 splitting longitudinally. Deep and peripheral centrosomes unlike. 



Fig. 5. Sperm-aster and sperm-nucleus. Nucleus elongated in the direction of its 

 aster, and pointed. Position of egg-aster indicated by dotted outline. 



Fig. 6. Germ-nuclei fused into a single (?) cleavage nucleus. First cleavage spin- 

 dle forming. Chromosomes being drawn to the spindle by tlie rays 

 which penetrate the interior of the fused germ-nuclei. Occasional 

 nucleoli show chromosomes attached to them. 



