THE CHROMOSOMES IX THE OOGEXESIS, 



FERTILIZATION AND CLEAVAGE OF 



COREID HEMIPTERA. 



CHARLES V. MORRILL. 



I. INTRODUCTION. 



Tin- n-ci-iit i onclu-ions regarding sex-production based on the 

 IHK lr.tr dimorphi-m of the spermatozoa in the trarheate- have 

 invoked certain assumptions regarding oogene-i- and cleavage 

 which, though inaile in conformity with main- well-determined 

 facts, are -till in need of more adequate support from direct 

 observations. Tin- principal of these assumption- i- that in the 

 formation of tin- polar bodies, the diploid chromosome-groups 

 oi i IK- female an- reduced to haploid groups that are alike in all 

 the matin s. Further, since the spermato/oa are >t two 



sorts, the embryos produced would be correspondingly different 

 .nid tin- diltctvnce should be apparent from a study of the em- 

 br\onic inn lei. At present, however, the complete chnnno-ome- 

 le ha- been uorked out in only two groups of tracheates, the 

 ph\ Hi ixer.m- and aphids. In the phylloxeran-. Mor-.m 'o>, '< " i 

 ha- tiait-d the lull history of the chromosomes through several 

 genera tion- and the combined observations of Stevens ('050, 'o6a, 

 oil \dii Baehr '08, 'oi>) and Morgan ('09) practically completes 

 the . \( le iii the aphid-. The very recent observations of Boveri 

 and C.nlii k hough as yet published only in brief outline, 



-how that in ll<:>rak\s, a nematode, the chromosome-cycle i- 

 -iniilar to that a--umed for many insects and bears the same 

 relation to -ex-production, while Baltzer ('08) has found that in 

 -ea-un hin-. the conditions are the reverse of those in insects, 

 the ei;i;- Uiii- dimorphic and the spermatozoa all of one kind. 



The pre-eiit \\oik 1 was undertaken with the hope of demonstrat- 



I !n~ 1. 1. .1.1. in \\a- begun in the zoological laboratory of Columbia t "iiivi-i>ity 

 .in.l . ..inpli -ti -.1 in th.- anatomical laboratory of the College of Medicine, Syracuse 

 t "nivi T-ity. A part ni" the material was collected while occupying a John D. Jones 

 N l...lai-hi|> I.M, m at tin.- liinlivuical laboratory, Cold Spring Harbor. N. V., during 

 t In- Mimiiu-r ol' n;"7. an. I a \Vi>tar Institute room at the Mann. Biological Labor 



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