488 JEAN REDMAN OLIVER 



The caudal tube was held by the earlier writers, such as 

 Koelliker ('67), to be derived from the nuclear membrane, a view 

 upheld today in a modified form by Schoenfeld ('00) for the 

 bull, and by Van Molle ('06 '10) for the squirrel, the mole, the 

 guinea-pig and the mouse. According to the last cited author 

 a hernia-like circular fold of the nuclear membrane is formed, 

 which grows backward as a double- walled tube. Between the 

 lamellae of this tube is a clear fluid derived from the nuclear 

 sap. When the annulus migrates downward along the axial 

 filament it takes with it the inner membrane of this tube, evagi- 

 nating it completely. At the same time the whole wall con- 

 tracts so that the final length of the single-walled tube is the 

 same as when in the earlier double-walled condition. 



Opposed to this conception is that of the derivation of the 

 caudal tube by a process of cytoplasmic differentiation alone, as 

 held by Lenhossek ('98), Meves f'OO), Duesberg ('08 '10), Retzius 

 ('09 b '09 c), Branca ('09),»Le Plat ('10) and many others. All 

 of these agree that the caudal tube arises with comparative 

 abruptness, its earliest beginnings being more or less obscure and 

 difficult to follow. Meves has given the most detailed account 

 of the process. According to his observations on the guinea-pig 

 a series of filaments inserted in a circle upon the nuclear mem- 

 brane at first appear. These are at first oblique, giving an hour- 

 glass outline to the whole structure. Progressively they become 

 more nearly parallel to the main axis of the future spermatozoon 

 and are united by a homogeneous substance into a hyahne tube, 

 the 'Manschette.' The fibrillar stage appears to be very short 

 and has been seen in detail by but few observers besides Meves. 

 My study of the events in the fur seal gives a complete con- 

 firmation of the origin of the caudal tube as held by Meves, the 

 early fibrillar stages shown in figures 16 to 19 being clearly visible 

 though not abundant, in my preparations. 



In respect to the ultimate fate of this structure two views are 

 held. According to Koelliker ('67) , Meves ('99) , Schoenfeld ('00) , 

 Duesberg ('08), Branca ('09), and Le Plat ('10) it disappears 

 without leaving any trace, and its function throughout is prob- 

 lematical. Retzius ('09) has emphasized the fact that the caudal 



