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_Stenopelmatus._
FIG. 80. Telophase of second maturation mitosis.
81. Young spermatid, showing spindle-remains at _s_.
82. Spermatid showing a conspicuous chromatin element in nucleus, and spindle-remains (_s_) elongated.
83. Spermatid, showing centrosome (_c_) and divided spindle-remains (_s_ and _a_).
84. Older spermatid, showing centrosome (_c_), axial fiber of tail, and spindle-remains (_s_).
85. Spermatid, showing acrosome material (_a_) migrating to side of nucleus opposite centrosome.
86. Slightly older spermatid.
87. Later stage of spermatid, showing condensed chromatin, elongated centrosome (_c_), acrosome material (_a_), and spindle-remains (_s_).
88-89. Older spermatids, showing formation of acrosome (_a_) and middle piece (_m_).
90-92. More advanced stages.
93. Mature spermatozoon.
_Blattella germanica._
FIG. 94. Somatic cell from egg follicle, 23 chromosomes.
95. Spermatogonium, showing chromatin element (_x_) a.s.sociated with a nucleolus (_n_).
96. Same, prophase of mitosis.
97. Equatorial plate of spermatogonial mitosis, 23 chromatin elements.
98. Young spermatocyte, showing centrosome (_c_) and U-shaped element (_x_).
99. Young spermatocyte, element _x_ attached to one end of a long, fine spireme.
100. Coa.r.s.er spireme stage.
101-103. Bouquet stage.
104-105. Later spireme stage.
106. Various forms a.s.sumed by the combined nucleolus and element _x_; last figure from a giant cell.
107. Segmenting spireme.
108. Similar stage to fig. 107, one chromosome longitudinally split; element _x_ present.
[Ill.u.s.tration: STEVENS. PLATE III.
N. M. S. del.]
PLATE IV.
_Blattella germanica._
FIG. 109. Similar stage to figs. 107 and 108; chromosomes U-shaped and not longitudinally split; two centrosomes present (_c_).
110. Longitudinally split chromosomes.
111-113. Various stages in formation of cross-shaped tetrads.
114-117. Bent rods, U-shapes, split rings, pairs of rods, and rod-shaped tetrads (116), which are equivalent to the crosses of figs. 112-113.
118-122. Metaphase of first maturation division, showing the element _x_ in various positions.
123-127. First maturation spindle in metaphase.
128. Same in anaphase.
129-132. Late anaphase, showing element _x_ double in 129, and a lagging tetrad in 130.
133. Telophase, with the element _x_ in one daughter cell.
134-136. Prophase of second maturation mitosis, showing dyads and element _x_.
[Ill.u.s.tration: STEVENS. PLATE IV.
N. M. S. del.
BLATTELLA GERMANICA.]
PLATE V.
_Blattella germanica._
FIGS. 137-141. Dyads contracting for second maturation mitosis.
142. Equatorial plate of second maturation spindle, containing 11 chromosomes.
143-144. Same, with 11 chromosomes and the element _x_.
