472 L. V. DOMM AND MARY JUHN. 



V. SUMMARY. 



1. Unilateral castration in Brown Leghorn cockerels is followed 

 by compensatory hypertrophy of either the right or the left 

 retained testis when the operation is performed on birds aged 16, 

 24 and 32-40 weeks. 



2. The removal of the right or the left testis in chicks aged 

 one week caused a compensatory hypertrophy of the left retained 

 gonads only, after a period of thirty-one weeks, in our experi- 

 ments (Table I.). 



3. There may be a certain period before increase in weight of 

 the retained gonad over the controls becomes manifest; the 

 length of this period is variable. 



4. The left retained testis shows a greater tendency towards 

 hypertrophy than does the right. 



5. There seems to be a difference in the weight of the left 

 and the right normal testes; this is in favor of the left gonad in 

 very young birds and then gradually seems to become shifted 

 to the right testis as the bird becomes older and reaches maturity. 



6. A tentative suggestion is made, that there may be some 

 relation between the greater amount of germinal epithelium in 

 embryonic left testes and the greater tendency towards hyper- 

 trophy of the left surviving gonad which is particularly manifest 

 when unilateral castration is performed on young birds. 



BIBLIOGRAPHY. 



1. H. Ribbert. 



'50 Ueber die kompensatorische Hypertrophie der Geschlechtsdriisen. Archiv. 

 f. Anat. u. Physiol., 120: 247-272. 



2. A. Lipschutz. 



'22 The So-called Compensatory Hypertrophy of the Testicle after Unilateral 

 Castration. The Jour, of Physiol., 56: 451-458. 



3. J. Benoit. 



'25 Sur 1'hypertrophie compensatrice apres castration unilaterale chez le Coq 

 domestique. C. R. de 1'Acad. de Sc., 180: 1690-1692. 



4. J. Firket. 



'14 Recherches sur 1'organogenese des glandes sexuelles chez les oiseaux 

 Archives de Biol., 29: 201-345. 



5. R. Semon. 



'87 Die indifferente Anlage der Keimdriisen beim Hiihnchen und ihre Differ- 

 enzierung zum Hoden. Jen. Zeitschr. f. Naturwiss., 21. 



6. C. H. Swift. 



'16 Origin of the Sex Cords and the Definitive Spermatogonia in the Male 

 Chick, 20: 375-410. 



