THE SPERMATOGENESIS OF APLOPUS MAYERI. 
By H. E. Jorpan. 
INTRODUCTION. 
The object of the present investigation is primarily to trace the history 
of the accessory chromosome through the various stages in the process of 
spermatogenesis in the phasmid Afplopus mayer. Incidentally an effort is 
made to present in as concise a form as appears compatible with complete- 
ness the several salient points of similarity and difference between the 
growth and maturation phenomena as they obtain in Aplopus and other 
Orthoptera previously studied. 
The study of the accessory chromosome is approached from the stand- 
point of its possible relation to the determination of sex as first suggested 
by McClung (1901), and its support of the hypothesis of the morphological 
and physiological individuality of the chromosomes as enunciated by Rabl 
(1885) and later extended by Boveri (1902), Sutton (1902), Montgomery 
(1904), Baumgartner (1904), and others. 
This study purports to be mainly a cytological one. The microscopic 
anatomy, as also the anatomical relations of the gonads of Aplopus mayeri, 
is essentially similar to that so well described and illustrated by de Sinéty 
(1901) in the case of Leptinia attenuata and Menexenus obstusespinosus. 
Nor shall I here attempt a review of the literature on the subject of the 
“ heterochrosomes ” (Montgomery, 1901). This has been very excellently 
done by several cytologists (Sutton, 1900; McClung, 1902; Montgomery, 
1904) and more recently and very completely by Boring (1907). 
It seems necessary to state at this point only that the chromosome, for 
which I have adopted McClung’s (1901) terminology, “ accessory chromo- 
some,” has been described as a closely similar structure in many of the in- 
sects, especially the Hemiptera, under the several names of “ odd chromo- 
some” (Stevens) ; “chromatin nucleolus” (Montgomery) ; “ chromosome 
speciale” (de Sinéty) and “ heterotropic chromosome” (Wilson). 
MATERIAL AND METHODS. 
The material upon which the investigation is based was obtained from 
Loggerhead Key, Florida, through the kindness of the Carnegie Institution 
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