16 THE NAUTILUS. 



Special attention would be directed to the fact that this 

 record includes four instances of the male discharging sperm, 

 one in case of Lasmigona complanata (Say), two instances of 

 Lastena suborbiculata (Say) and one of Lampsilis cardia (Raf.), 

 all observed in the laboratory aquarium. In case of both com- 

 planata and suborbiculata this physiologic fact disproves the 

 report that, like their nearest allies, Lasmigona compressa (Lea) 

 and Lastena ohiensis (Raf. ), are hermaphroditic. Another in- 

 stance of sperm discharge for Lampsilis cardia was observed in 

 nature. This discharge was observed as a tiny stream of milky 

 white cysts. Upon examination with a lens, magnifying 385 

 diameters, these cysts were observed to be hollow globular 

 masses of sperm, each cyst revolving through the water by 

 means of the flagella of hundreds of sperm cells thrust out 

 through the matrix. It was the pleasure of the author to ver- 

 ify the observations of Dr. A. E. Ortmann, (191 la, p. 319), 

 in discovering on several instances the female of this same 

 species, (cardia), buried in the gravel with only the siphons, 

 mantle flaps and two blackish ovisacs exposed. The ribbon- 

 like flaps waved to and fro in an undulating manner and occas- 

 sionally a white leaf-like conglutinate would be discharged. It 

 was noted that the marsupia of this species were sterile and 

 receptive on occasion of the sperm discharge. 



Another physiologic observation, made in the laboratory, 

 should be mentioned here in connection with the reproductive 

 functions of the Naiades and that was in case of the rotary 

 motion of the late embryos of Pleurobema obliqmim coccineum 

 (Conrad) and of Lastena ohiensis (Raf.). These are noted to 

 be revolving clock-wise around one axis at the rate of about fifty 

 times per minute. This phenomenon may be common with all 

 species of Naiades and the reason why only seldom seen may 

 be because of the short duration of this embryonic activity 

 which may be necessary in the final development into the 

 glochidial stage, for it was only in this structural stage that this 

 rotary motion was seen. 



The most prolific and continuous breeder, found by the 

 writer, is Lasmonos fragilis. This mussel, being the predomi- 

 nant form in northwest Missouri and thus being the most 



