32-t PROCEEDINGS OF THE ACADEMY OF [April,. 



Wilson, E. B. 1902. The Cell in Development and Inheritance. 



1905. (a) Studies on Chromosomes: I. The Behavior of the Idiochromosomes 

 in Hemiptera. Jour. Exp. Zool., II. 



1905. (b) Studies on Chromosomes: II. The Paired Microchromosomes, 

 Idiochromosomes and Heterotypic Chromosomes in Hemiptera. Jour. 

 Exper. Zool., II. 



1906. Studies on Chromosomes: III. Sexual Difference of Chromosomes 

 Group in Hemiptera. with some Consideration on Determination and 

 Inheritance of Sex. Jour. Exper. Zool., III. 



Description of Plates XXII-XXVII. 



All the figures, with the exception of the text figure, page 10, were drawn at 

 the level of the table with the aid of a camera lucida. A Zeiss microscope 

 was used with a Xo. 8 ocular and a l(i mm. oil immersion objective, giving a 

 magnification of 2,250 diameters. The plates have been reduced to about 

 one-third their original size. 



Plate XXII — Callosamia promethea — Figs. 1-4 — Sp< rmatogonial rest stag' s 



showing stages in the disappearance of the net knot. 

 ' Fig. 5 — Spermatogonia] spireme. 

 Fig. (i — Spermatogonia! equatorial plat-' showing 38 chromosomes. 

 Fig. 7 — Spermatogonia! metaphase. 

 Fig. s — Spermatogonia! anaphase. 

 Figs. 9 and 10 — Spermatogonia! telophase showing formation of nuclear 



membrane. 

 Fig. 11 — Formation of spireme preparatory to synizesis. Spermatocyte. 

 Fig. 12 — First spermatocyte, synizesis. 



Fig. 13 — First spermatocyte, synizesis (smear preparation). 

 Fig. 14 — First spermatocyte, chromatin in loops. 

 Figs. 15- is — Degenerating cells. 



Fig. 19 — First spermatocyte, early post, synapsis (smear preparation). 

 Figs. 20-21 — First spermatocyte, late post-synapsis (smear preparation). 

 Fig. 22^First spermatocyte, spireme divided into reduced number of 



chromosomes. 

 Figs. 23-26 — Fir<t spermatocyte, growth sta.se. 

 Fig. 26 — First spermatocyte, smear preparation showing continuity of the 



chromosomes. 

 Figs. 24, 25 and 29 — First spermatocyte, ciliated centrosomes. 

 Fig. 27 — First spermatocyte, split segments. 

 Figs. 32, 33 — First spermatocyte, ring formation. 

 Fig. 28 — First spermatocyte, condensation of rings. 

 Fig. 34 — First spermatocyte, formation of plasmosome. 

 Figs. 35-3S — First spermatocyte, stages in prophase of first maturation 



division. 

 Fig. 39 — First spermatocyte, smear preparation, late prophase showing 



plasmosome with chromatin band. 



Plate XXIII — Callosamia promethea — Fig. 40 — First spermatocyte, equatorial 



plate, 19 chromosomes. 

 Fig. 41 — First spermatocyte, polar plate, 19 chromsomes. 

 Fig. 42 — First spermatocyte, metaphase, lateral view. 

 Fig. 43 — First spermatocyte, anaphase. 

 Fig. 44 — First spermatocyte, telophase. 

 Fig. 45 — Second spermatocyte, polar \iew. 

 Fig. 46 — Second spermatocyte, prophase, chromatin scattered, chromatin 



granule present. 

 Fig. 47 — Second spermatocyte, prophase, rearrangement for second division, 



zwischenkorper marks cell axis. 

 Fig. 48 — Second spermatocyte, prophase, two chromatin granules present, 



ciliated centrosomes. 



