lOO ULLIE. 



EXPLANATION OF PLATE VI. 



Fig. 82. Embryo slightly older than Fig. 79 ; seen from the ventral surface. 

 Invagination of larval mantle begun. 



Fig. 83. Obliquely sagittal section of stage of Fig. 82 ; v.p., ventral plate. 

 Fig. 84. Median sagittal section of same stage. 



Fig. 85. Ventral half of transverse section through stage of Fig. 82. Shell 

 •not drawn in. 



Fig. 86. Horizontal section through ventral wall of same stage. 

 Fig. 87. Section slightly dorsal to Fig. 86 (v. Fig. 84 for plane of section). 

 Fig. 88. Median sagittal section of the young glochidium of Unio complanata. 

 Fig. 89. Transverse section of the same stage, passing through the intestine. 

 Fig. 90. Same series ; three sections (7 \ /x) in front. 



Fig. 91. Horizontal section of same stage, showing opening of thread-gland 

 into mantle cavity. 



Fig. 92. February Glochidium of Anodonta, anterior view ; only a mere 

 fraction of thread drawn. 



Fig. 93. Ventral view of same; shell gaping. 



Figs. 94-97. Four transverse sections from stage of Fig. 93. Sections asym- 

 metrical, passing further forward on left side. 

 Fig. 94. Through cerebral ganglia. 



Fig. 95. Three sections posterior to Fig. 94; oes., rudiment of oesophagus. 

 Fig. 96. Five sections posterior to Fig. 94. 

 Fig. 97. Six sections posterior to Fig. 94. 

 (Sections 7.5 ^ thick.) 



