ORTMANN: A MONOGRAPH OF THE NAJADES OF PENNSYLVANIA 307 
in the anal opening. The dark brown color of the glochidia contrasts strongly 
with the whitish, semitransparent tissue at the base of the gills, and thus the supra- 
branchial canals are easily traced by this color. The same phenomenon was seen 
in a specimen of Quadrula undulata, collected July 8, 1909, where also numerous 
loose glochidia, but of whitish color, were found in the suprabranchial canals of all 
four gills. On May 13, 1910, a specimen of Symphynota costata was found, also in 
the act of discharging loose, brown glochidia through the suprabranchial canals. 
The glochidia were not plentiful in the canals. This specimen was not preserved. 
An additional case, corresponding closely to the instances just mentioned, was 
observed on July 12, 1910, in Anodonta imbecillis. Finally, I have observed’ in 
alcoholic material of five specimens of Strophitus edentulus collected April 22 and 
24, 1908, a similar condition. But here there were whole placentule as well as free 
glochidia in the outer suprabranchial canals, and in no case were they very 
numerous. 
Entirely different from these are the following observations: 
In a gravid female of Ptychobranchus phascolus (collected August 31, 1906; 
probably unusually delayed in the discharge), there were on the margin of the 
right marsupium about half a dozen placentee protruding through and beyond the 
edge, that is to say, in the act of escaping from the marsupium through openings 
in the outbulging edge of the gill. This peculiar fact suggested to me the idea, 
that the discharge of the glochidia might take place here not by the natural channels 
and the anal opening, but by breaking through the edge of the marsupium into 
the branchial cavity, and thence through the branchial opening into the surrounding 
water. I consequently made a careful search among my material for additional 
specimens caught in the same act, and I found indeed such evidence for this “un- 
natural” discharge. What I was able to ascertain is that there are actually, at 
the time of the discharge, holes breaking through the edge of the marsupium, which 
thus furnish an outlet for the glochidia. ‘These holes may be seen macroscopically, 
and are also shown quite satisfactorily in some of my slides. The best slides I 
have are made from Lampsilis luteola and multiradiata (See Pl. LX XXVIII, figs. 
18 and 20). But I also possess such from Lampsilis nasuta and Obovaria circulus, 
which show this feature, although less distinctly. I remember further, to have 
noticed macroscopically these holes in Lampsilis alata, but I did not succeed in 
obtaining a satisfactory slide, and I have a slide of Lampsilis gracilis (See Pl. 
LXXXVIII, fig. 16), which shows, as I believe, the closing up of these holes after 
the discharge of the contents of the ovisacs. 
In 1910 I found similar instances. A specimen of Ptychobranchus phaseolus, 
