380 J. E. BLOMFIELD. 



next the hollow of the tube and extends into {o) tlie flagellum 

 or caudal filament (/'). 



The bar forms the middle piece (Mittel Sti'ick, of Schweigger 

 Seidel), while the caudal filament helps to complete the tail of 

 the spermatozoon. The caudal filament would appear to be 

 formed out of the plasma which tills up the hollow of the tubu- 

 lar polyplast. The further changes consist in a growth of the 

 cephalic nodule over the rest of the nucleus in the form of a 

 cap, and the elongation of the middle piece, which becomes 

 freed from the cell body while the caudal filament remains 

 attached to its distal extremity. 



The ampulla now consists of a mass of tube-like polyplasts, 

 each with its basilar nucleus, and each built up by a bundle 

 of spermatozoa, whose tails project towards the lumen of the 

 ampulla. As the next step, these are discharged, and now 

 nothing remains except the blastophoral cell. Each blasto- 

 phoral cell consists of plasma holding a basilar nucleus towards 

 its base^ and a body, which arose during the later development 

 of the spermatozoa, placed about the middle of cell, and called 

 by Semper " the problematic body/' 



Nothing is known about this body. It does not appear to 

 consist of fat, but possibly it is connected with the atrophy of 

 the blastophoral cells and ampulla which now takes place. (See 

 Semper's * Arbeiten,' 1875.) 



We now pass to the description of Spermatogenesis in 

 Mammals, contained in a paper by Dr. George Renson in the 

 ' Archiv de Biologie,' tome iii, fascicule ii, 1882, according to 

 which in its main outlines the process is strikingly similar to 

 what we have before described in other classes. 



The paper in question commences with a resume of the 

 work of previous observers, especially V. Ebner, Sertoli, and 

 V. la Valette St. George. A few pages are devoted to descrip- 

 tions of methods which are those in ordinary use, and then the 

 author commences the process as seen in the Rat, an animal 

 which all observers acknowledge to be the best for obser- 

 vation. 



lie first describes the elements which arc seen in a pre[)ara- 



