404 HARRY H. CHARLTON 



The first maturation division separates the dumb-bell-shaped 

 chromosomes transversely (fig. 39), and probably represents a 

 reduction division, as the idiochromosomes go to one pole undi- 

 vided. The second division of the autochromosomes is clearly 

 a longitudinal one (fig, 55), while the idiochromosomes separate 

 transversely, so that it would seem that this represents an 

 equational division of the autochromosomes and the separation 

 of the idiochromosomes one from the other. 



The centrosome 



The single- or double-rod type of centrosome has been described 

 in a variety of forms. Meves ('98) and Buder ('15) have 

 described them in the Lepidoptera, and Sewertzoff (Meves, '00) 

 in Orthoptera, and Korff ('01) in the Coleoptera. In plants 

 Von Mottier ('98) found them in the tetraspore mother cell of 

 Dictyota dichotoma. Korff also found them in the sperm cells 

 of the domestic hen and duck, while Hortega ('16) figures them 

 for the ganglion cells and brain of man. 



Von Mottier does not consider them homogeneous, but to arise 

 from small granules. In the beetles, Korff shows them to be 

 very like those found in Lepisma domestica, but he has not 

 reported any granule in relation to the rods at any time. He 

 finds the limbs of the V separating in the late telophase and 

 appearing parallel to the polar axis in the spindle. In Lepisma 

 domestica the centrosomes are always oblique to the axis, but 

 parallel to each other. 



We have seen the centrosome first as one or two small granules, 

 then as double rods with or without end granules, and still later 

 as single rods which only occasionally show a granule. In very 

 rare cases, instead of single rods, the centrosome consists of 

 several granules in the polar position. From these observations 

 the form of the centrosome would seem to be a variable quantity. 

 It is interesting in this regard that Korff ('01) was only able to 

 see the V-shaped centrosome in the sperm cells of the drake and 

 rooster, while all the other cells of the body showed centrosomes 

 consisting of single granules. 



