BAUMGARTNER : SPERMATID TRANSFORMATIONS. 59 



the thought that they are the same stage, and his fibers are re- 

 mains of the spindle. His fig. 43, of course, agrees with my 

 fig. 25 ; and fig. 43 may correspond to figs. 26 or 14, only that 

 his stain is weaker. 



Meves's investigations are the most extensive of the recent 

 ones on the nebenkern. He has used Paludina and Pygsera as 

 his objects. The consideration of the mitochondrion in the 

 spermatocytes I shall pass over, as it is not within the bounds 

 of this paper ; yet I hope to study the earlier generations of my 

 material, and shall then compare the results. In Meves's de- 

 scription of Paludina, I find but one point in which it agrees 

 with Gryllus. The head of the young spermatozoon in Paludina 

 has a clear space in the center filled with nuclear fluid, which 

 remains till the head begins to stretch. In Gryllus it is hollow 

 until maturity. 



In Paludina the nebenkern in one kind of spermatids is formed from threads 

 made up of mitochondria — small, round bodies identical with St. George's cyto- 

 microsomes and Erlanger's centrodeutoplasm. These threads change to vesi- 

 cles, which, reduced to four, closely surround the centrosome as it lengthens 

 into the middle piece. At first they form a four-cleft cylinder, but finally a 

 single sheath. An idiozome and spindle remains are seen in the spermatid. 

 They persist for awhile, and the former changes into the acrosome. In Pygcera 

 Meves finds two kinds of spermatids, distinguished by a small difference in size. 

 The larger forms the typical spermatozoon. The spindle remains form a " Spin- 

 delrest korper," which is soon lost. The ends of the mitochondrion chains form 

 a ring of dark mass surrounding a clear space. The ring is broken by radiating 

 clear spaces. These spaces collect and unite into larger vacuoles, which sur- 

 round the darker center. Finally there is only a dark ball with a surrounding 

 clear space shut in by a ring. The centrosome with attached axial filament 

 fastens itself to the nucleus; then both begin to grow longer. The axial fila- 

 ment passes over the surface of the ring surrounding the ball — the "mitochon- 

 drion korper" or nebenkern. This body elongates a great deal|; then the darker 

 mass puts forth numerous threads which surround the axial filament. 



As to Pygtrra, the peculiarity is the complete agreement of 

 his "mitrochondrion korper" and my nebenkern in appearance 

 and behavior for a part of the transformation and their complete 

 disagreement in the other part. The question with me is, Do 

 the two bodies whose final stages are so similar originate so dif- 

 ferently, or has one of us mistaken the origin of the body ? 



Since reading Meves's paper I have carefully reexamined my 

 material, and I am positive that I am right as to the origin of 

 the nebenkern ; but, on the other hand, I would not say that 

 Meves is wrong in his observations, as in doing so I should fall 

 into the same error which I think Meves himself has made. In 



