-l'I .ENES1S OF THK .MM<|o: j .1 



due to tin- i.i' i ill. it many of the chromosomes do not lie at right 

 the I iii.- of vision and must, therefore, appear fore- 

 -hortcned in ,m outline drawing. 



l-efore di the individual characteristics of the various 



chromo-ome- , n in metaphase, it might be well to gh 



l.rii-l" review of thi-ir history in the prophase. The spermatocvte 

 < lii-om- nteen in number. Of these, sixteen are 



l.i\al< in element- formed by the end to end union of univalent 



imosomes during the tetophase of the last spermatogonial 

 di\i-ion Hl.ickman. :o^. :o5, op. cit.}. The seventeenth element , 

 'In < liron;,,-<imc, is univalent in character, being de- 



ii\d dinctU from .1 si ngle specialized chromosome, the accessory 

 chromosome oi tl matogonium. The growth period following 



i|>-i- i Duration in Stolopendra, and during this period 



ill o| i In- ( In. mi* are grouped together to form a nucleolu 



like -inn tun- to which I have given the name karyosphnv. 

 \\hile in tin- karyi-pluTe the chromosomes arc so closely a^. 



d ih.it i luir indi\idual outlines cannot be distinguished \\iili 



'I In >, lio\\e\rr, enter the karyospherc as distinct in- 



dixidnal- .uid I.i -e from it as definite chroma tin segment-. 



-iinil.tr in every resj>ect except for their greater size. These 



Is \\oiild -rnn to argue f(>r, rather than against, the individu- 



.ilit\ oi the chromosomes during this stage. 



In tin- proph.i-r the chromosomes arising from the karyosph< 

 .tn i\|.it,ill\ long. -l-inler threads of granular chromatin, which 

 in\ .iri.tl'K -h'\\ near their middle an interruption of the chro- 

 in.itin thi- n |'K -niting the point at which the chromosomes 

 united during -\ n.t|i-i-. The two spermatocyte divisions al\\ 



li in .i loiigitudin.il and a cross division of these bivalent 

 rlrimnt-. The longitudinal division as a rule seems to occur 

 lir-t. although, a- \\ e -hall see later, this is not invariable, CM n 

 tor the ordinary chromosomes. The cross division or reduction 

 di\i-ioii iv-uh- in the separation of entire spermatogonical chro- 

 nio-oim--, tin' di\ i-ion occurring at the point at which they united 

 dining synapsis. However, although the results of these di- 

 \ i-ion- .tic tin -ame for all of the chromosomes (with the excep- 

 tion- to In- iioud later), the changes through which the tetrad 

 pass in the projih.i-e and the shapes they assume during the pro- 



