The nuclear components of the sex cells of four species of cockroaches. 515 
greater metabolic activity tban the other bodies and that the plas- 
mosome represents some of the material involved. 
The four species of cockroaches which have beeu studied show 
a close similarity in their spermatogenesis, the details of the various 
processes yarying between very narrow limits. On the other hand, 
comparison with other Hexapoda belonging to the same Order, shows 
certain decided dilferences. In this one Order, the methods of arriv- 
ing at the same ends are varied and a greater ditference is some- 
times found between different species of the same Order Orthoptera) 
than between species belonging to different Orders or even classes. 
An instance of this is seen in the case of Periplaneta, which in 
some respects diflfers more widely from that of Brachystola or Hip- 
piscus than from Tomopteris. Apparently, therefore, Korschelt and 
Heider’s distinction between pre-reduction and post-reduction is of 
value only for descriptive purposes, and is of quite minor impor- 
tance as far as the final result of the maturation mitoses is concerned. 
The writer has prepared the present paper under the direction 
of Professor E. B. Wilson of Columbia University, to whom the 
writer extends his wärmest thanks for the painstaking care he has 
given to its production and for the sympathy he has shown throughout 
the course of its development. The writer wishes likewise to thank 
Professor Ivix Sickels of the College of the City of New York for 
kindness shown him in Connection with this work. 
Zoological Laboratories, Columbia University in the City of New 
York, U. S. A. 
March 1, 1909. 
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Allen, C. 1J. 04. Chromosome reduction in Lilium canadense. Botanical 
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of Hydrophilus piceus (L.). Arch. f. Zellf. 2:181. 
Auerbach, ’96. Untersuchungen über die Spermatogenese von Paludina. 
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Baumgartner, 04. Some new evidences for the individuality of the chromo- 
somes. Biol. Bull. 8. 
Berry, '06. The accessory chromosome in Epeira. Biol. Bull. 11. 
Bonnevie, ’07. "Heterotypical" mitosis in Nereis limbata Ehlers. Biol. Bull. 
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