BAUMGARTNER : SPERMATID TRANSFORMATIONS. 57 



changed the name nebenkern to mitosome. The centrosome lies in front of the 

 nucleus and forms the point of the head. This he calls the nebenkern. From 

 the spindle remains arise two bodies. A large, fibrous one from the equatorial end 

 has a clear space around it and the axial filament passes through it. It soon 

 elongates and forms the tail. This is the large mitosome. The other is much 

 smaller and arises from the polar end of the spindle fibers. It takes its place in 

 the angle between the large mitosome and the nucleus. Here it persists till the 

 nucleus begins to elongate, when it lengthens and surrounds the basal end of the 

 spermatozoon tail. This is the small mitosome. 



Platner ('85) saw a true nebenkern. I have already criticized 

 the use of the word "nebenkern," as the name for the spindle 

 remains in the spermatocytes. Platner himself later denied 

 the nuclear origin of the nebenkern. His results ('86, 2) 

 agree with mine concerning the uniting, converging, staining 

 and bending of the spindle-fiber remains and their passing to 

 the tail. Again, Platner ('89,1) probably followed the cen- 

 trosome and attraction sphere, as well as the nebenkern, in the 

 second part of the paper on Helix and Paludina. In the pancreas 

 the body is a result of secretion, and is not a nebenkern. In 

 Pygxra Platner 's large mitosome is the real nebenkern, as 

 shown by its fibrous structure, its surrounding clear space and 

 destiny. His small mitosome is what I have described as the 

 acrosome, and he is mistaken as to its final use. The body he 

 called centrosome in the nucleus is the persisting accessory 

 chromosome. Such would be my interpretation of his figures. 



Henking ('91) has followed the spermatid changes in Pyrrhocorix quite care- 

 fully. He finds that the fibers between the chromatin masses are separated into 

 peripheral fibers and central spindle fibers. The first, a part of the second and 

 the yolk mass, forms the nebenkern, which passes down over the axial filament. 

 The rest of the central fibers form the mitosome. This takes its position at the 

 angle between the nebenkern and the nucleus. On the surface of the nucleus it 

 passes to the anterior end, then back to its original position. A piece now is con- 

 stricted off and disappears, while the rest, increasing its affinity for stains, again 

 wanders to the anterior pole of the nucleus, and becomes the acrosome. 



The large amount of yolk substance is a disturbing element 

 in Pyrrhocoris , but the nebenkern agrees with that of Gryllus in 

 having the same origin and destiny, as does also the acrosome 

 in fate and position. Besides, there is much similarity in the 

 stages, as seen by comparing Henking's fig. 63 with my fig. 25, 

 and his fig. 85 with my fig. 32. 



Wilcox ('95 and '96) described the spermatid metamorphosis in Calo}Henus. 

 The interzonal fibers, a long, striated body composed very plainly of distinct 

 fibers, contracts longitudinally, and the corners round themselves off, and this 

 forms the nebenkern. It loses its fibrous structure, comes close to the nucleus, 



