SPERMIOGENESIS OF THE PRIBILOF FUR SEAL 491 



Le Plat considers that the two small granules at the end of 

 the axial filament are merely thickenings of the anterior ends 

 of the latter and that they are not of centrosomal origin. 



From a consideration of the diagrams it is readily seen that 

 the fundamental nature of the transformations of the centrioles 

 is the same throughout, the differences appearing in smaller 

 details, and it is not at all improbable that studies upon other 

 forms may bring out still further complications. No other branch 

 of cytology, however, presents greater difficulties than the study 

 of these minute objects, and great caution must be used in 

 criticism and in generalization from a limited number of facts. 



In conclusion, I desire to express my indebtedness to Prof. F. 

 M. MacFarland for the constant interest he has taken in my 

 work, and for the final revision of my manuscript, and to Mrs. 

 Olive H. MacFarland for her great kindness in redrawing the 

 figures which illustrate it. 



BIBLIOGRAPHY 



Ballowitz, E. 1891 Die Bedeutung der Valentin'schen Querbander am Sper- 

 matozoenkopfe der Saugethiere. Archiv f. Anat. u. Physiol. Anat. Abt. 

 p. 193. 



1908 Zur Kenntnis der Spermien der Pinnipedier. Anat. Anz., Bd. 33, 

 10, p. 253. 



Benda, C. 1891 Neiie Mittheilungen iiber die Entwickelung der Genitaldriisen, 



etc. Verh. d. physiolog. Gesellsch. zu Berlin Archiv. f. Anat. u. 



Physiol. Physiol. Abt. p. 549. 



1906 a Die Spermiogenese der Monotremen. Semon Zool. Forschungs- 



reise in Australien. Denkschr. Med. Nat. Ges., Bd. 6, 2. p. 413. 



1906b Die Spermiogenese der Marsupialier. Ibid., p. 439. 

 BiONDi, D. 1885 Die Entwicklung der Spermatozoiden. Archiv f. Mikr. Anat., 



Bd. 25, p. 594. 

 Branca, A. 1909 Sur la manchette caudale dans la spermiogenese humaine. 



Bibliog. Anat., Bd. 19, p. 85. 

 DuESBERG, J. 1908 La spermiogenese chez le rat. Archiv f. Zellforschung., 



Bd. 2, p. 137. 



1910 Nouvelles recherches sur I'appareil mitochondrial des cellules 



seminales. Archiv f. Zellforschung, Bd. 6, p. 40. 

 Heidenhain, M. 1907 Plasma und Zelle. Bardeleben's Handbuch der Ana- 



tomie des Menschen, Bd. 8, 1. 



1909 Ueber die Haltbarkeit mikroskopischer Praparate, etc. Zeitschr. 

 f. Wissensch. Mikros., Bd. 25, p. 398. 



Hermann, F. 1889 Beitrage zur Histologie des Hodens. Archiv f. Mikr. Anat., 

 Bd. 34, p. 58. 



THE AMERICAN JOURNAL OF ANATOMY, VOL. 14, NO. 4 



