238 T. H. MORGAN. 



Fig. i, C, with that of the cock-feathered Campine in Fig. 9. 

 The bird was killed May 9, 1920. On the right side in the posi- 

 tion of the testis there was found a very small piece of testicle- 

 like tissue. In addition there were two sacks rilled with black 

 matter, attached loosely to the mesentery near the old position 

 of the testis. 



In this " small " Campine a piece of testis was found, as 

 stated, in the situs of the removed testis. The histological struc- 

 ture of this regenerating testis is entirely similar to that in the 

 regenerating piece of the Campine that was castrated when cock- 

 feathers were beginning to appear. The description of the latter 

 may serve for that found in the small Campine ; both pieces agree 

 in all details : the lutear cells have disappeared entirely and large 

 numbers of small lymphocytes are produced in the mesenchyme. 

 The spermatogenetic process is normal in the tubules that had 

 been left, but the spermatozoa are degenerate. New seminal 

 tubules are arising, but they are reduced to the Sertoli cells, no 

 spermatogonia being present. 



Besides this piece of regenerating testis there were found dark 

 masses of tissue. In these masses there has been an active pro- 

 liferation of connective tissue cells, which form strands placed in 

 all directions. Some of the cells in this stroma are filled with 

 large drops of a fat-like substance. There is an active hema- 

 topoiesis in these masses, the large lymphocytes being abundant, 

 both within and outside the blood vessels. Large accumulations 

 of normal and degenerated erythrocytes occur in the blood ves- 

 sels, hence the dark color of the masses. The aspect of the latter 

 suggests that they are portions of the degenerated epydidimis, a 

 few tubules of the latter being present, although their epithelium 

 is almost entirely degenerated. 



The extent to which the second " larger " bird had changed 

 by Sept. 9, is shown in Fig. 4, A. His new back and saddle 

 feathers were long and pointed. He continued to become more 

 cock-feathered, but his comb began to grow, and it became evi- 

 dent that some of the testis had been left. He was opened under 

 ether. Attempts were made to remove the pieces, but the opera- 

 tion was not successful as shown by the condition of the comb 

 which remained large. It was however very pale. The bird 



