610 kobbht h. bo wen 



Notes on the Centkioles and the Transformations 

 OF THE Spermatid Nucleus. 



I have found the centrioles in the Icpidopteran spermatid 

 exceedingly difficult to demonstrate Avith any degree of satis- 

 faction. I am, therefore, unable either to confirm or deny the 

 extraordinary account given by Gatenby. His statement 

 that one of the centrioles is cast off ought certainly to receive 

 the most careful examination. It is usually an easy matter 

 in the insect spermatid to demonstrate the centrioles in some 

 form or other at the point of insertion of the tail filament, but 

 in the moths which I have studied even this has usually proved 

 impossible. Mgs. 28-30 show at the end of the axial filament 

 a small granule, which is presumably the centriole(s), and 

 Gatenby's fig. 51 seems to show something similar. I wish 

 only to point out here that in the Lepidoptera, as noted by 

 many workers, the head of the spermatid is bent very sharply 

 at the point of insertion of the axial filament, so that the original 

 insertion seems to be near the anterior side of the nucleus rather 

 than at its base, as is customary. Subsequent stages indicate 

 that this may actually be the case, the centriole perhaps shifting 

 its position to the base of the nucleus when the latter elongates 

 to form the sperm head. 



The breaking up of the chromosomes at the close of the 

 second maturation division offers no points of special interest. 

 The chromatic material becomes eventually spread out in a thin 

 and slightly uneven layer on the inner wall of the nucleus 

 (figs. 1, 4, 8, and 13), somewhat as in the Heiniptera (Bowen, 

 1922 a). During the later stages in the spinning out of the neben- 

 kern halves, a rearrangement of the chromatic material is 

 accomplished. This results in the appearances showTi in 

 figs. 15 and 16, in which one gets the impressi(m that a portion 

 of the nucleus is being cleared up by the ^\-ithdrawal of the 

 chromatin. Tliis seems actually to be the nature of the process, 

 for subsequently the nucleus appears divided rather sharply 

 into two areas, one of which is perfectly clear and transparent, 

 while the other retains the chromatic material probably still 



