■60 KANSAS UNIVERSITY SCIENCE BULLETIN. 



his discussion of the literature he has forced every description 

 to agree with his ideas, or has declared that the author has de- 

 scribed some extra-nuclear organ as a nebenkern which is not a 

 nebenkern. Thus by implication, if not by direct statement, he 

 says that a nebenkern never comes from the spindle remains. 

 With due respect to his ability and long experience as an inves- 

 tigator, I must say that Meves is mistaken in this. St. George 

 himself traced the cytomicrosomes back to the spindle remains. 

 Besides, the many investigators whom I have cited above can- 

 not be mistaken as to the origin of the nebenkern. In my own 

 material I am positive that there is a direct passing of the in- 

 terzonal fibers over into the earlier stages of the nebenkern. 



That the body which forms the tail covering does not come 

 from the spindle remains in all cases, I am willing to admit. 

 Meves has cited many investigators, especially on vertebrates, 

 whose results favor such an opinion. The spindle remains do 

 not change into a nebenkern even in all Arthropods, as Black- 

 man ('01) finds no nebenkern, nor anything in anywise resem- 

 bling it, in Scolopendra. 



From my study of the results of other investigators, it is evi- 

 dent to me that there are at least two general methods for the 

 formation of the covering for the spermatozoon tail. One of 

 these plans will harmonize Meves's mitochondrion korper, Er- 

 langer's centrodeutoplasm, Heidenhain's pseudo-chromosomes, 

 and other similar structures. The other will show that Plat- 

 ner's large mitosome, Paulmier's blackberry stage and my 

 striated nebenkern are only different stages of the spindle re- 

 mains changing into the tail covering. 



V.— Summary. 



1. The chromosomes of the second spermatocytes break up 

 and the chromatin becomes diffused all through the nucleus. 

 Later the chromatin collects in granules again and finally forms 

 the walls of the tube-like spermatozoon head. 



2. The spindle fibers break loose as the clear space is formed 

 around the chromatin mass. They unite and contract, becom- 

 ing fewer, thicker, and shorter. These bend and form the 

 "striated nebenkern." The fibers break up and sometimes 

 show a blackberry appearance. Soon there is a collection of 

 darker material at the center, surrounded by a clear space, 



