NOTES ON A FRESH-WATER MEDUSA FOUND IN STALLWORTH TUSCALOOSA, ALABAMA

¹ From the Department of Zoölogy, University of Alabama, and the Department of Biology, New York University

1. Fresh-water medusæ were observed in Stallworth Lake, an artificial body of water near Tuscaloosa, Alabama. They were first seen by the writer on September 14, 1928. They disappeared on October ninth of the same year and have not been observed since.

2. The hydroid stage was not found.

3. A description of the lake where the medusæ were found is given.

4. A historical survey of the fresh-water medusæ is made.

5. The medusæ agree very closely with Craspedacusta ryderi as described by Payne (1924). There are certain differences which may be developmental or due to dissimilar environmental conditions. The medusæ are assigned to the species C. ryderi.

6. The tentacles are grouped into four, instead of the three previously used groups.

7. Sections of the gonads demonstrated that all the medusæ examined were males.

8. Observations on the spermatogenesis of C. ryderi are included.

9. Since all gonads obtained were from adult medusæ, no information concerning the origin of the germ cells can be given.

10. The primary spermatocytes are only very slightly larger than the spermatogonia.

11. There is a meiotic stage in which the chromatin is stained only very poorly with iron hæmatoxylin.

12. There seem to be twelve chromosomes at each pole of the late anaphases of the primary spermatocytes.

13. Some portions of the sperm are stained more intensely by Flemming's triple method and others by iron hæmatoxylin. Thus the two methods give different appearances to the sperm.

14. Tails are not visible on sperm in fixed and stained preparations.