280 ALLEN : POLYODON SPATHULA 



ence depend on the number and the distribution of these abnormal 

 ions as a function of their rate of damping. 



It is further shown that only a few constants need be deter- 

 mined in von Schweidler's equations to represent the observa- 

 tions with a good degree of accuracy. The remaining theories 

 do not seem to be adequate to represent the present observations. 



FISHERIES. — Notes on the breeding season and young of Polyodon 

 spathula. Wm. F. Allen, Institute of Anatomy of the 

 University of Minnesota. 



Since the appearance of Mr. Allis's recent papers in the Anatom- 

 ischer Anzeiger on the " Pseudobranchial and carotid arteries of 

 Polyodon^ in which he made use of a specimen 130 mm. (5.5 

 inches) long, I have received several letters of inquiry as to when 

 and where this material was obtained. 



It is a well-known fact that nothing is known concerning the 

 early development of Polyodon, and very few specimens under 

 6 inches in length have been obtained. 



In 1904, when employed by Mr. Allis, I was sent to the Missis- 

 sippi River for the purpose of obtaining all of the Ganoid material 

 possible. After considering various localities on the Mississippi 

 River system, the junction of the Ohio with the Mississippi, at 

 Cairo, was selected as probably the most favorable place for 

 obtaining this material. 



For an entire year the bars of these rivers were seined at all 

 times of the day and night; also the adjacent overflow lakes, 

 sloughs, and small streams were seined at regular intervals thruout 

 the year, and during the early spring a number of adults were 

 obtained from hoop-nets placed in the channel on the Missouri 

 side of the Mississippi, with the hope of obtaining sexually mature 

 individuals whose eggs could be fertilized and the embryos reared. 



So far as early embryonic material was concerned my results 

 were a failure, but a great many specimens from 6 to 12 inches 

 long were obtained, and about 25, varying in length from 4 to 

 6 inches were secured. Considerable data were obtained con- 

 cerning the habits that may be of value in future search for this 

 material. 



