f* 
106 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
45. In the second division the chromosomes form no equatorial 
plate; they are dragged along one by one to each pole, fourteen being 
drawn to one pole and fourteen to the other. 
46. At the close of the second maturation division, the intermediate 
fibers, especially those of the central spindle, having more or less 
chromatin granules adhering to them, persist as the nebenkern. The 
nebenkern consequently is a mitosome. 
47. The nebenkern does not form the middle piece of the sperma¬ 
tozoon nor the inner sheath of the axial filament, but persists for a 
considerable time at the base of the nucleus, after which it is gradually 
absorbed, moving bodily down along the axial filament forming 
vacuoles at regular intervals along its path. 
4S. The axial filament is not a single fiber, but a greatly attenuated 
central cytoretieulum in connection with the nucleus. 
«/ 
49. The centrosome finally takes up its position at the head of 
the nucleus; as the latter elongates into the mature spermatozoon 
head, the centrosome with the anterior part of the sperm cytoplasm, 
becomes imbedded in the cytoplasm of the head nurse-cell as the 
acrosome. 
50. I have seen nothing that could positively be identified as a 
middle piece. 
51. The mature spermatozoon is a greatly compressed and elon¬ 
gated cell, with its nucleus correspondingly elongated, with its fourteen 
chromosomes arranged in a row, and the centrosome at the anterior 
end. 
Historical Survey of the Literature. 
Malpighi is one of the first to give an account of the sexual organs 
of insects. He studied the silkworm and described the male genital 
organ of the larva. It was some time before the ovary was discovered, 
the red pigment of the testis making it more easily seen with the naked 
eve. 
V 
Swammerdam was unable to find the ovary; but he described the 
testis of Vanessa urticae as two kidney-shaped bodies. These he 
claims could not be found again in the pupa, as he found only a red 
body occupying about the same position. 
Bessels (’ 67 ) gives a correct explanation of this in calling attention 
