No. 393.] THE LIFE HABITS OF POLYPTERUS. 727 
Aug. 3. Three fish from Toela (salt water), one male, two 
females. 
Aug. 4. One small male, one large male, one female which 
had shot her eggs. 
Aug. 5. Five females, three with eggs, two had shot eggs ; 
all below average size. 
Aug. 8. A pretty pair, male and female, apparently caught 
in same net. Female without eggs, male with striking copula- 
tory anal fin. 
Aug. 9. Three not designated. 
Aug. 10. Two not designated. 
Aug. 15. One not designated. 
Aug. 21. Two, both females full of eggs. 
Aug. 24. One large female with eggs. 
Aug. 25. One. 
Sept. 1. Female at Damietta with eggs. 
A review of the above list shows plainly that the greatest 
difficulty we found in getting the developmental stages at 
Mansourah by artificial fertilization was the scarcity of mature 
males. There were only twelve males to fifty-eight females. 
Although sexually mature individuals of both sexes will be 
seen to have been brought in the same day, it was found 
exceedingly difficult to keep one promising specimen alive and 
healthy until an equally promising mate could be secured. As 
many as fifteen fruitless attempts were made to raise larve, by 
mixing sperm that moved actively with eggs which appeared 
ripe (although these could never be shaken from the ovarian 
stalks in large numbers). 
This practical difficulty in keeping Polypterus in confinement 
is due to the fact that it is not an especially hardy fish. It will 
not survive more than three or four hours out of water, and 
only then under the most favorable conditions ; that is, cov- 
ered with damp grass and weeds. The Nile catfishes Clarias 
and Bagrus, on the other hand, retain an unimpaired vitality 
after twice as long an exposure to similar conditions. It is 
well known that these catfishes have accessory branchial 
organs, and some species make considerable journeys overland. 
Physiologically at least, therefore, Polypterus has not evolved 
