REPRODUCTION IN THE UNIONID^ 
97 
There is considerable diversity in size among glochidia even 
from the same genus, as represented by the series of text-figures 
(fig. 1, A'N), all drawn to the same scale, the most striking being 
the difference between the two species of Plagiola (G and^) 
and between Lampsilis rectus and gracilis {K and L). Harms 
('09) who has studied the exceedingly minute glochidia of Margar- 
itana margaritifera, finds that they are exclusively gill parasites 
Fig. 1. Figures showing relative sizes and shapes of the shells of a series of glo- 
chidia, belonging to the following species: A, Symphynota complanata, 0.30 X 0.29 
mm.; B, S. costata, 0.39 X 0.35 mm; C, Anodonta cataracta, 0.36 X 0.37 mm; D, 
Lampsilis (Proptera) alatus, 0.41 X 0.23 mm; Quadrula meta nerva, 0.19 X 0.18 
mm; F. Q., pustulosa, 0.32 X 0.23 mm; G, Plagiola elegans, 0.09 X 0.075 mm; 
H, P. securis, 0.31 X 0.23 mm;/, Quadrula ebena, 0.15 X 0.14mm; J, Q. plicata, 
0.21 X 0.20 mm; K, Lampsilis gracilis, 0.085 X 0.075 mm; L, L. rectus, 0.24 X 0.20 
mm; M. Obliquaria reflexa, 0.23 X 0.225 mm; N, Unio gibbosus, 0.22 X 0.19 mm. 
THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 9, NO. 1. 
