Seasonal Changes in the Testes of the Passerine Bird,Phainopepla nitens lepida.

This study was undertaken to determine the histological changes which take place in the testes of the Phainopepla during an entire year. It was hoped that such changes which were noted could be correlated in some way with the behavior of the birds.

The collection of Phainopeplas for this study was started on November 26, 1937, and has been carried on periodically up to the present time, December, 1938. The gonads were removed while still warm and fixed in Bouin's solution and then carried through the usual paraffin method. They were sectioned and stained, using Delafield's hematoxylin and eosin for some, and Heidenhain's iron hematoxylin for others.

The testes showed a gradual increase in size from a minimum of one mm on November 26, 1937, to their maximum size of 8 mm, which was recorded on May 14, 1938. While the general trend throughout the spring was upward in size some individual variations were noted.

The testes showed no rapid increase in size until March 24th, and few sperms appeared in the lumina of the tubules until May 12th. This is rather unusual for in most seasons on the desert breeding starts in February and is at its height by the end of March. Although the rains were late and it stayed cool much later than usual this year it does not seem that the reproductive cycle should have been slowed to such an extent. Yet this seemed to be the true condition, as it was further substantiated by extensive field excursions during that period.

In the winter testis (Fig. 1) the size was about 1 mm, the tunica albuginea was thick, as was also the tunica propria. The seminiferous tubules were small and there was an abundance of intertubular material, composed chiefly of connective tissue cells with possibly a few interstitial cells among them.