142 ALICE M. BORING. 



gland cells in the interstitial tissue. Poll, in his studies of hybrid 

 birds, speaks of the increased development of the interstitial 

 gland composed of cells of epithelial nature in contradistinction 

 to the connective tissue. Ceni, in his account of experiments 

 with feeding ducks on caffeine and removing the cerebrum, 

 speaks of an increase of the amount of interstitial tissue at the 

 expense of the cells of the seminal tubules and mentions groups 

 of epithelial cells called interstitial glands. On the other hand, 

 Loisel distinctly states that he finds no evidence of activity in 

 the cells of the interstitial tissue of birds at any time of year, 

 but finds a fatty secretion formed by the Sertoli cells. Mazzetti 

 finds no more evidence of secretory granules in the cells of the 

 interstitial tissue than in the cells of the seminal tubules. He 

 claims that interstitial cells are derived from connective tissue 

 cells and gives an interesting list of variations in the number of 

 interstitial cells in different animals and in the same animal at 

 different times of year. Kirkbride states that the number of 

 interstitial cells in the testes of newborn infants is very variable. 

 Gudernatsch describes a case of hermaphroditism in man where 

 the interstitial tissue of the testicular portion of the ovotestis 

 was enormously developed, and yet the secondary sexual charac- 

 ters were such that the individual was usually regarded as a 

 female. 



So the question of the origin, nature and function of the inter- 

 stitial cells has been by no means settled. Now if it is a general 

 law that the interstitial cells and secondary sexual characters 

 are causally interrelated, one would certainly expect to find 

 abundant interstitial cells in a bird with such marked secondary 

 sexual characters as the domestic chicken. 



METHODS. 



Just-hatched chicks were used first, as there are some indi- 

 cations that there may be a differentiation in respect to certain 

 secondary sexual characters at that early age. The chicks 

 were all Barred Plymouth Rocks from the Maine Experiment 

 Station stock, not a day old. The gonads are easily cut off 

 from the surface of the kidney with scissors. They were fixed 

 in Gilson's, Flemming's and Hermann's solutions, these two osmic 



