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STUDIES IN SPERMATOGENESIS

PART II.
(PAGES 33-74. PLATES VIII-XV.)
A COMPARATIVE STUDY OF THE HETEROCHROMO-
SOMES IN CERTAIN SPECIES OF COLEOPTERA,

HEMIPTERA AND LEPIDOPTERA, WITH
ESPECIAL REFERENCE TO

SEX DETERMINATION.

BY N. M. STEVENS

WASHINGTON, D. C.:
Published by the Carnegie Institution of Washington
October, 1906

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STUDIES IN SPERMATOGENESIS.—II.

A COMPARATIVE STUDY OF THE HETEROCHROMOSOMES IN CERTAIN SPECIES
OF COLEOPTERA, HEMIPTERA, AND LEPIDOPTERA, WITH ESPECIAL
REFERENCE TO SEX DETERMINATION.

By N. M. STEVENS.

INTRODUCTION.

In Part I of this series of papers, the spermatogenesis of five species
belonging to four different orders ot insects was considered. In two
species of Orthoptera an ‘‘accessory chromosome’’ was found; in
Tenebrio molitor, one of the Coleoptera, an unequal pair of chromo-
somes was described; in the other species no heterochromosomes were
discovered. The apparent bearing of the chromosome conditions in
Tenebrio molitor on the problem of sex determination has led to a
further investigation of the germ cells of the Coleoptera. One of the
Hemiptera homoptera and two of the Lepidoptera have also been
examined for comparison with the Coleoptera and the Hemiptera
heteroptera.

METHODS.

As a result of previous experience with similar material, only two
general methods of fixing and staining have been employed: (1) Fix-
ation in Flemming’s strong solution or Hermann’s platino-aceto-osmic,
followed by either Heidenhain’s iron-hematoxylin or Hermann’s
safranin-gentian staining method (Arch. f. mikr. Anat. 1889). (2)
Fixation after Gilson’s mercuro-nitric formula, followed by iron-
hematoxylin, Delafield’s hzmatoxylin and orange G, Auerbach’s
combination of methyl green and acid fuchsin, or thionin.

The iron-hematoxylin with either mode of fixation gives by far the
most satisfactory preparations for general study. The other stains
were used mainly for the purpose of distinguishing between hetero-
chromosomes and plasmosomes in resting stages of the nucleus.

33

34 STUDIES IN SPERMATOGENESIS.

COLEOPTERA.
Trirhabda virgata (Family Chrysomelidae).

Two species of 77irhabda were found in larval, pupal, and adult
stage on Solidago sempervirens, one at Harpswell, Maine, the other at
Woods Hole, Massachusetts. The adult insects of the two species
differ slightly in size and color, the germ cells mainly in the number
of chromosomes, 77irhabda virgata having 28 and 7rirhabda cana-
densé 30 in spermatogonia and somatic cells.

In Trirhabda virgata, the metaphase of a spermatogonial mitosis
(plate vii1, fig. 3) contains 28 chromosomes, one of which, as in 7ene-
brio molitor is very much smaller than any of the others. ‘The mater-
nal homologue of the small chromosome is, as later stages show, one
of the largest chromosomes. In Zenedrio the unequal pair could not
be distinguished in the growth stages of the spermatocytes. In
_ Trirhabda it has not been detected in the synizesis stage (fig. 4), but
in the later growth stages (figs. 5-7) this pair is conspicuous. in
preparations stained by the various methods cited above, while the
spireme is pale andinconspicuous. The size of the heterochromosome
pair varies considerably at different times in the growth period, and
in some nuclei (fig. 7) both chromosomes appear to be attached toa
plasmosome. The ordinary chromosomes assume the form of rings
and crosses in the prophase of the first maturation mitosis (fig. 8), but
usually appear in the spindle as dumb-bells or occasionally as tetrads
(fig. 10), or crosses (fig. 11). The unsymmetrical pair is plainly seen in
figures 9 and 11, but is not distinguishable in apolar view of the meta-
phase (fig.13). In the anaphase (figs. 14-16) the larger and the smaller
components of the pair separate as in Tenebrio. ‘This is, therefore,
clearly a reducing division as far as this pair is concerned, and prob-
ably for all of the other pairs, though neither the synapsis stage nor the
prophase forms are so clear on this point as in some of the other species
studied. Figures 17 and 18 show metaphases of the two classes of
second spermatocytes, the chromosomes varying somewhat in form in
different preparations and even in different cysts of the same prepara-
tion. An early anaphase of this mitosis is shown in figure 19; here
the small chromosome is already divided. It was impossible to find
good polar views of the daughter plates in the two classes of second
spermatocytes, but it is evident from figure 19 and other similar views of
the second spermatocyte spindle that, as in 7exebrvio, one-half of the
spermatids will contain one of the derivatives of the small chromo-
some, the other half one of the products of its larger homologue.

TRIRHABDA VIRGATA. 35

Sections of male pupze were examined for equatorial plates of
somatic mitoses. Figure 1 is a specimen of such plates. As might
be expected, this figure resembles quite closely the spermatogonial
equatorial plate (fig. 3) in number, form, and size of chromosomes, the
small one being present in both. Figure 2 is from the follicle of a
young egg; here we find 28 chromosomes, but no small one. ‘The
chromosome corresponding to the larger member of the unequal pair
in the. male evidently has a homologue of equal size in the female. ‘The
chromosome relations in the male and female somatic cells are there-
fore the same as in Tenebrio molitor, and must have been brought about
by the development of a male from an egg fertilized by a spermatozoon
containing the small chromosome, and a female from an ege fertilized
by a spermatozoon containing the larger heterochromosome,

Trirhabda canadense.

In 77irhabda canadense the spermatogonial chromosomes are invaria-
bly smaller than in 7. vrgata, but similar size relations prevail. The
spermatogonial plate (fig. 21) contains 30 chromosomes, 29 large and
1 extremely small. In the growth stages the association of the two
unequally paired chromosomes with a rather large plasmosome is more
evident than in 7. virgata (figs. 22-23). In this species the unequal
pair is more often found at a different level from the other chromo-
somes in the early metaphase of the first maturation mitosis (fig. 24),
but it later comes into the plate with the other chromosomes (figs.
25-27), and divides earlier than most of the other bivalents (fig. 27).
In a polar view of this metaphase the largest chromosome often appears
double (fig. 28); in a front view it is a tetrad as in J. virgata, figure
10. Figure 29 is the equatorial plate of a metaphase in which the
larger component of the unequal pair has been removed in sectioning.
The daughter plates of a first spermatocyte in anaphase (fig. 30) show
the separation of the components of the heterochromosome pair; and
equatorial plates of the resulting two classes of second spermato-
cytes (fig. 31) show the same conditions. Figures 32 and 33 are
prophases of the second division, figure 33 showing the small chromo-
some ready for metakinesis. It was impossible here also to get good
drawings of daughter plates of the second spermatocytes to show the
content of the two classes of spermatozoa, but there is no doubt that
all of the chromosomes divide in the second mitosis, giving one class
of spermatids containing the small chromosome, the other class its
larger homologue. _

No male somatic cells were found in mitosis, but they would, if
found, show the same conditions as in the spermatogonia. One of

36 STUDIES IN SPERMATOGENESIS.

many good equatorial plates from egg follicles (fig. 20) shows 30 large
chromosomes, indicating an equal pair in place of the unequal pair of
the male.

Chelymorpha argus (Family Chrysomelidae).

This species was found in larval and adult stages on Convolvulus
arvensis at Harpswell, Maine, in July and August. It shows the
same conditions as 7rivhabda and Tenebrio, so far as the unequal pair
of chromosomes is concerned, and is especially favorable for study
of synapsis stages. The number of chromosomes in the spermatogo-
nia (plate 1x, fig. 36) is 22. Here the components of the unequal
pair are the small spherical chromosome and one of the several chro-
mosomes third in size, forming a comparatively small unsymmetrical
bivalent (figs. 47-49). The spermatogonia occupy the outer end
of each follicle, and next to them comes a layer of cysts in which the
chromosomes from the last spermatogonial division are closely massed
in the form of short deeply staining fos at one side of the nuclear
space (fig. 37). Following this synizesis stage comes one in which
some of the short loops have straightened, their free ends extending
out into the nuclear space (figs. 38 and 39). Figure 40 shows the
nucleus of a slightly later stage in which the free ends of two straight-
ened chromosomes are on the point of uniting. In figures 41 and 42
the point of union of homologous chromosomes is indicated in some
cases by a knob, in others by a sharply acute angle. In a slightly
later stage (fig. 43), when all of the short loops have straightened and
united in pairs, the point of union is no longer visible, all of the loops
being rounded at the bend and of equal thickness throughout. My
attention was first called to this method of synapsis by the con-
spicuous difference in number and length of loops in the synizesis
stage compared with the later bouquet stage just before the spireme is
formed. Following the synapsis stage shown in figure 43 comes one
in which the loops lose their polarized arrangement and unite to form
a continuous spireme (figs. 44 and 45). In this form, the heterochro-
mosome pair could not be distinguished until the spireme stage,
and it is, therefore, uncertain whether these chromosomes remain
condensed after the last spermatogonial divisions and are hidden
among the massed and deeply staining loops of the synizesis and syn-
apsis stages, or whether they pass through the same synaptic phases
as the other chromosomes, condensing and remaining isolated at the
beginning of the spiremestage. An early prophase of the first matu-
ration mitosis (fig. 46) shows segments of the spireme longitudinally
split, and in some cases transformed into crosses which show a trans-
verse division also. Most of the equal bivalents have the dumb-bell

CHELYMORPHA ARGUS. 37

form in the spindle (figs. 47-49). One is ring-shaped, the ring being
formed by union of the free ends of the segment so that the spindle
fibers are attached to the middle of each univalent chromosome (fig.
49). This method of ring formation, like that described by Mont-
gomery (’03) for the Amphibia, is of very frequent occurrence in the
spermatocytes of the Coleoptera. The dumb-bells are so bent at the
ends (fig. 52) that the spindle fibers, here also, are attached at or
near the center of each univalent component of a bivalent chromo-
some, and the separated, univalent chromosomes go to the poles of the
spindle in the form of Vs. As in Zezebrio the heterochromosome pair
is late about coming into the equatorial plate (figs. 47-48), but it does
finally take its position with the others (fig. 49) and separates into
its component parts somewhat earlier than the other bivalents
(figs. 52, 53). Figures 50 and 51 show polar views of the metaphase,
the smaller element (x) being the unequal pair. The chromosomes
in late anaphase are too much crowded to give clear drawings. As
in all the beetles so far studied there is no rest stage between the two
maturation divisions, but the late anaphase of the first mitosis passes
over quickly into the second spindle. Figures 54 and 55 are typical
equatorial plates of the second division, one showing the small chro-
mosome (s), the other its mate more nearly spherical than the others
(2). An anaphase including the small chromosome is shown in figure
56. Asin the species previously described the spermatozoa are evi-
dently dimorphic.

Female somatic equatorial plates from egg follicles are shown in
figures 34 and 35 ; 22 chromosomes are present and no one is without
an equal mate.

Odontota dorsalis (Family Chrysomelidae).

Odontota dorsalis is a small leaf-beetle found on Robinia pseudacacia.
The chromosomes are comparatively few in number, 16 in the sperma-
togonia (figs. 58 and 59), and of immense size when one considers the
smallness of the beetle. In some of the spermatogonial cysts many of
the chromosomes are V-shaped as in figure 58, while in others all, with
the exception of the small one, are rod-shaped as in figure 59, which
looks like a hemipteran equatorial plate. The spermatogonial resting
nucleus (fig. 60) contains a large plasmosome (pf), but no condensed
chromatin. The synizesis and synapsis stages are similar to those
in Chelymorpha (figs. 61 and 62). The spireme stage (figs. 63, 64)
contains, in addition to the pale spireme, a very conspicuous group
consisting of a large plasmosome with a large and a small chromo-
some attached to it. In the prophase, before the nuclear membrane
has disappeared, this group is easily distinguished from the other

38 STUDIES IN SPERMATOGENESIS.

dumb-bell and ring-shaped bivalents (figs. 65-67). In preparations
much destained (fig. 67) the small chromosome component of the
group retains the stain longer than the larger one. ‘The spindle in
prophase (fig. 68) is much elongated and the 8 chromosomes are often
spread out upon it so as to beeasily counted. In the early metaphase
the parachute-like heterochromosome group is always nearer one pole
of the spindle (plate x, figs. 69 and 70). The equatorial plate often
shows both the larger component of the pair and the plasmosome (fig.
71). Figures 72-74 show the metakinesis of the heterochromosome
bivalent. In figure 74 the two unequal elements are completely sepa-
rated and the plasmosome has disappeared. The equatorial plates of
the two resulting kinds of second spermatocytes appear in figures 75
and 76. In the anaphase of the second division all of the chromo-
somes are divided quantitatively as may be seen in figures 77 and 78.
A few dividing male somatic cells were found in the walls of the
testis. Figure 57 (plate 1x) is an equatorial plate from one of these.
The chromosomes are like those of the spermatogonia (figs. 58 and 59),
15 large and 1 small. No dividing female somatic cells were found.

A few drawings of developing spermatids are given to show the
transformations of a peculiar body which seems to be characteristic of
insect spermatids. Figure 79 is a very young spermatid showing only
diffuse chromatin in the nucleus. The nucleus soon enlarges (fig. 80)
and a large dense body (7) appears which stains like chromatin with
various staining media. A little later (fig. 81) the chromatin forms
a homogeneous, more or less hemispherical or sometimes crescent-
shaped mass which stains aneven gray in iron-hematoxylin. In
addition the nucleus contains a body (7) smaller than in the preceding
stage, but staining thesame. As the nucleus condenses and elongates
to form the sperm head, a light region containing this deeply staining
body is seen on one side (figs. 82, 83). A little later the body is
divided into two, which appear sometimes spherical (fig. 84), some-
times elongated (fig. 85). As the sperm head elongates still mote,
approaching maturity, these bodies diminish in size (figs. 86, 87) and
ultimately disappear. A cross section of the sperm head at such a
stage as figure 87 shows the chromatin in crescent shape with material
which stains very little within (fig.88). The chromatin-like body
described above was observed in 7enebrio in a stage corresponding to
figure 81, and it was thought that the larger body seen in some cases
and the smaller one in others might be the larger and smaller hetero-
chromosomes, but a study of this element in more favorable material
disproves that supposition by showing that the different sizes are
merely different phases in the evolution of the body. Throughout its

ODONTOTA DORSALIS. 39

history it stains like dense chromatin, and my only suggestion as to its
origin is that it seems, from a study of this and other species of beetles,
to bea derivative of the chromatin of the spermatid, increasing in size
for a time, then decreasing, and finally breaking up into granules and
dissolving in the karyolymph. Whether it has any function connected
with the development of the spermatozoon, or whether it is merely
material rejected from the chromosomes, as in many cases in oogen-
esis, one can only surmise.

In one testis a peculiar abnormality was found. In all of the perfect
spermatogonial plates two small chromosomes were present (figs. 89,
go). Nineteen such plates were counted in five different cysts. All
of the equatorial plates of the first spermatocytes showed 8 chro-
mosomes, as usual. In a few favorable growth stages (fig. 91) the
two small chromosomes were seen to be combined with the larger
heterochromosome and a plasmosome, and one first spermatocyte
spindle was found in which the same combination could be clearly
seen (fig, 92). All of the second spermatocyte metaphases in which
a small chromosome occurred, contained two small ones, making 9 in
all (fig. 93). The others contained 8 large chromosomes, as usual.
The only explanation suggested by the conditions is that somewhere
in its history, the small chromosome had undergone an extra division,
and that ever afterward the two products behaved like the one small
heterochromosome of a normal individual. The chief interest in this
abnormality centers in the fact that the two small chromosomes of
this specimen behave exactly like the usual single one, emphasizing
the individuality of this particular heterochromosome. Both evidently
have the same individual characteristics and affinities as the one in
other cases.

Epilachna borealis (Family Coccinellidae),

Epilachna borealis was found in abundance on squash vines at
Woods Hole, Massachusetts, in September. The testes, unlike
those of most of the Coleoptera, consist of many free follicles similar
to those of the Orthoptera. The germ glands were rather far
advanced, but some good spermatogonial and spermatocyte cysts
were found. In figure 94, a spermatogonial metaphase, the small
chromosome is shown with 17 larger ones. The heterochromosome
pair appears in condensed form in the spireme stage (fig. 95), andagain
in the first maturation spindle (figs. 96, 97). The varying forms of
the ordinary chromosomes are shown in figure 98. Figures 99 and
I0oo are equatorial plates of the first mitosis. The unequal pair is
shown by itself in figure 1o1, and the separation of the heterochronio-

40 STUDIES .IN SPERMATOGENESIS.

somes is seenin figure 102. Hquatorial plates of the second division,
one containing the small chromosome (0), are shown in figure 103. A
prophase of the same division (fig. 104) proves that the small chromo-
some divides quantitatively like the others. It was interesting to find
here and there in this material whole cysts in which the nuclei were
like those described by Paulmier (’99) for Azasa ¢ristis (plate xI1It, fig.
14) as cells which were being transformed to serve as food for the
growing spermatids (figs. 105, 106). The only occasional appearance
of these cysts seems to me to preclude their being a special dispen-
sation to furnish the spermatids with nutrition during their transfor-
mation. ‘Their appearance and size make me suspect that they are
giant spermatids due to the failure of one of the spermatogonial or
spermatocyte mitoses. The smaller chromatin body seems to corre-
spond to that described for the spermatids of Odontota dorsalis.

Euphoria inda (Family Scarabaeidae).

Of Euphoria inda only one male was captured, but the numerous
testes furnished abundant material in desirable stages. The sperma-
togonial equatorial plate (fig. 107) contains 20 chromosomes of which
the two smallest (/ ands) form the unequal pair. The resting sperma-
togonium contains a two-lobed plasmosome (fig. 108). The growth
stages are similar to those in Zezedrvzo in showing no distinct bouquet
stage, but there is aspireme stage in which the heterochromosome pair
is clearly seen (fig. 109). Figure r1o (plate x1) is an early prophase,
and figure 111 one in which the unequal pair appears with a tetrad and
several dumb-bell forms. The prophase of the spindle, as in Odontota,
is much elongated (fig. 112). In figures 113-116 the small heterochro-
mosome pair is shown in various positions with reference to the other
chromosomes of the metaphase of the first spermatocyte. Figure 117
shows it more deeply stained than the others in the equatorial plate.
This pair divides in advance of the others, and the larger and smaller
elements are plainly seen nearer the poles in anaphase than the other
univalent chromosomes (figs. 118-120). Daughter plates of the first
spermatocyte are shown in figure 121, and equatorial plates of the
second spermatocyte in figure 123. Figure 122 shows the telophase
of the first division with the spindle for the second division forming.
In figures 124 and 125 we have daughter plates of the two classes of
second spermatocytes, showing the content of the two equal classes of
dimorphic spermatozoa, as this was shown in Tenebrio. Figures 126
and 127 are anaphases showing the division of the heterochromosomes
(ands). Figures 128-130 are early stages in the development of the
spermatid showing the chromatin nucleolus (7) in various phases.

BLEPHARIDA RHOIS. AI

Blepharida rhois (Family Chrysomelidae).

The testes were rather too far advanced when this material was
collected and no dividing spermatogonia were present. The growth
stages (figs. 131, 132) show a faintly staining spireme and a hetero-
chromosome group similar to that of Odontota, a large and a small
chromosome attached toa large plasmosome. The spireme appears
to go directly over by condensation and segmentation into the dumb-
bell-shaped figures seen in the first maturation spindle (figs. 133, 134),
though cross-shaped bivalents occasionally occur (fig. 135). The
heterochromosome pair, slightly separated by plasmosome material, is
usually found at the periphery of the plate (figs. 133-136). Figure
137 is an exceptional anaphase in which the heterochromosome
elements are not mingled with the polar masses of chromatin. Figures
138 a and 6 are equatorial plates of the second mitosis, and figures 139
and 140 are pairs of daughter plates from second spermatocytes show-
ing again the dimorphism of the spermatozoa as to their chromatin
content. Asin several of the forms studied, material was collected for
examination of the somatic cells, but no favorable cases of mitosis were
to be found.

Silpha americana (Family Silphidae).

Only one male of this species was secured, but the large testes gave
all stages in abundance. The chromosomes, however, were very
small and too numerous, 4o in the spermatogonia (fig. 141). The
small chromosome is, nevertheless clearly distinguished in many of
these plates (s). The resting spermatogonium contains one very large
plasmosome and often one or two smaller ones (fig. 142, f). The
unequal pair is seen in the growth stages (figs. 143, 144), and may
frequently be seen outside of the equatorial plate of the first sperma-
tocyte spindle (fig. 146). In favorable sections it may also be found
in the plate among the other bivalents (fig. 147). Figure 145 is a
prophase showing the bivalent chromosomes still connected by linin
fibers. An equatorial plate of the first division is shown in figure
148, and a pair of corresponding plates of the second spermatocyte in
figure 149. The small heterochromosome divides in the second spindle
in advance of the others as seen in figure 150. ‘Therefore, although
this form is not especially favorable for detailed study on account of
the large number of small chromosomes, the conditions: are evidently
the same as in the other species gdescribed—an unsymmetrical hetero-
chromosome bivalent in the first spermatocyte, giving rise by the
second maturation division to equal numbers of dimorphic sperma-
tozoa, one class receiving the large heterochromosome, the other class
the small one.

42 STUDIES IN SPERMATOGENESIS.

Doryphora decemlineata (Family Chrysomelidae).

Doryphora decemlineata has been the most difficult one of the collec-
tion to work out satisfactorily. The chromosomes in the spermato-
gonial plates were in most cases much tangled, and the behavior of the
heterochromosome pair was such as to suggest an ‘‘ accessory chro-
mosome’’ rather than an unequal pair. Abundant material for the
study of somatic cells was at hand, but nothing favorable could be
found in the sections.

Two spermatogonial plates, containing 36 chromosomes, are shown
in figures 151 and 152 (plate x11). The small heterochromosome (s) is
slightly elongated. The synizesis and synapsis stages are especially
clear. The chromosomes, after the last spermatogonial mitosis go
over immediately into a synizesis stage consisting of a polarized group
of short loops, which later straighten and unite in pairs (figs. 153
and 154). From these loops are formed the spireme (figs. 155-158),
which splits and segments, producing various cross, dumb-bell, and
ring forms (figs. 159-163). As in most of the other species of
Coleoptera, the unequal pair is not distinguishable until the spireme
stage. Figure 162 is an unusual prophase in which all of the equal
pairs show a longitudinal split as well as a transverse constriction,
and the larger heterochromosome (/) is also split. Figure 163 shows
a somewhat later and more common prophase in which the unequal
pair, one ring, crosses, and dumb-bells may be seen. ‘This figure, as
well as figures 164-168, show the unequal pair in various relations to
the other chromosomes. ‘This pair in Doryphora consists of a large
\-shaped chromosome with a small spherical one attached to it in
different positions. When the small one is behind the V, the group
has the appearance of an orthopteran “‘ accessory.’’

Figures 169-171 show the separation of the two elements outside of
the equatorial plate, while in figure 168 the unequal pair is in line
with the other chromosomes. In figure 172, an anaphase, the unequal
elements are barely separated, while the metakinesis of the other pairs
is much further advanced.

Figures 173 and 174 are equatorial plates of the first division, one
showing only the larger element of the heterochromosome pair (fig.
174, x), the other both elements (fig. 173,/ and s). In the late
anaphase (fig. 175) the larger heterochromosome is often seen outside
of the polar mass, reminding one again of the ‘‘accessory’’ in the
Orthoptera. Occasionally it is found in some other isolated position
(fig. 176). Equatorial plates of the second division show the same
conditions as in the other species; some contain the larger hetero-
chromosome, others the smaller one (fig. 177, a and 6). It was impos-

DORYPHORA DECEMLINEATA. 43

sible to draw anaphases of the second division from a polar view and
the lateral view showed nothing unusual, merely the longitudinal
division of all of the chromosomes.

The spermatids show some interesting variations from the other
species which have been examined. In figures 178 and 179 we have
telophases of the second spermatocyte, showing centrosome and archo-
plasm (fig. 178) and certain masses of deeply staining material in the
cytoplasm (fig. 179, a,). Figures 180 and 181 are young spermatids
showing the archoplasm from the second spindle (a,) and a smaller,
more deeply staining mass (a,), derived from the irregular masses of
the earlier stage (fig. 179, a,). In figures 182 and 183, the axial fiber
has appeared and the larger mass of archoplasm (a,) is being trans-
formed into a sheath. The other body remains unchanged. During
the following stages this smaller archoplasmic body (@,) lies in close
contact with the axial fiber and sheath (a,), and gradually decreases
in size (figs. 184-186) until it disappears in a slightly later stage.
The acrosome seems to develop directly out of the cytoplasm. The
enigmatical body (a,), which is probably archoplasm from the first
maturation spindle, as it is not found in the cytoplasm of the first
spermatocyte, may serve as nutriment for the developing axial fiber.
The sperm head has a peculiar triangular form, staining more deeply
on two sides.

Miscellaneous Coleoptera.

Considerable material from the spruce borers was collected at
Harpswell, Maine, but the species were not identified. Although
these insects were in the pupa stage, most of the testes were too old.
There were no dividing spermatogonia and few spermatocyte mitoses.
Most of the spermatocytes contained 10 chromosomes, one of which
was plainly an unequal pair. In a few testes the number was 11,
indicating that pupze of two species had been collected. Figure 187
shows the metaphase of first spermatocyte mitosis with the unequal
pair in metakinesis. Figures 188 and 189 are first spermatocyte
equatorial plates of the two species, containing 10 and 11 chromo-
somes respectively.. Figure 190 is a first spermatocyte spindle in
anaphase, showing the unequal pair behind the other chromosomes.
Figure 191 is an equatorial plate from a second spermatocyte, showing
the small chromosome. In figure 192 are shown several of the biva-
lent chromosomes, including the unsymmetrical pair, from nuclear
prophases of the first division, all from the same cyst.

Adalia bipunctata (family Coccinellidz), the common lady beetle,
has a very conspicuous pair of unequal heterochromosomes, as may be

44 STUDIES IN SPERMATOGENESIS.

seen in figures 193-197 (plate x111). This would seem to be a favorable
form for determining the chromosome conditions in somatic cells, but
no clear equatorial plates were found in either larve or pupze.

In Cicindela primeriana (family Cicindelidz) there are 18 chromo-
somes in the spermatogonium (fig. 198), one beingsmall. The hetero-
chromosome group is blended into a vacuolated sphere in growth
stages (figs. 199, 200). In the metaphase of the first division it is
trilobed, or tripartite (fig. 201), and in metakinesis, a small spherical
chromosome separates from a much larger V-shaped one (fig. 202).
Equatorial plates of first and second spermatocytes are shown in
figures 203 and 204. Wholecysts of giant first spermatocytes were
found both in growth stages (fig. 205) and prophases (fig. 206). Here
the heterochromosome group is plainly double (fig. 205), and the con-
ditions observed must have been due to the failure of a spermatogonial
mitosis to complete itself.

Several of the Carabide have been studied, and the material,
though not especially favorable, is interesting in that some members of
the family have an unequal pair of heterochromosomes, others an odd
one. Chlenius estivus (figs. 207-212), Chlenius pennsylvanicus (figs.
213-215), and Galerita bicolor (fig. 216) have the unequal pair, while
Anomoglossus emarginatus (figs. 217-223) has an odd heterochromo-
some (x), which behaves exactly like the larger heterochromosome in
other carabs.

In the Elateride and Lampyridee we also have examples of the
second type with the odd chromosome. ‘Two Elaters, species not
determined (figs. 224-229 and 230-235), have each 19 chromosomes
in the spermatogonia (figs. 224 and 230), and in the first spermatocyte
division an odd chromosome (x) which is in each case the smallest.
In the first of these Elaters, the female somatic number was determined
to be 20 (fig. 229). In the second Elater the pairs of second sperma-
tocytes, containing g and 10 chromosomes respectively in the two
cells, were in nearly every case connected as shown in figure 235,
one pair of chromosomes not having separated completely in the first
mitosis. Of Lillychnia corrusca (family Lampyridz) only the sperma-
togonial equatorial plate, containing 19 chromosomes (x, the odd one)
is given, as no material in maturation has yet been obtained, and a
comparative study of the germ cells of the Elateridee and Lampyridz
will be made as soon as suitable material can be secured.

In addition to the species of Coleoptera described here, two others,
Coptocycla aurichalcea and Coptocycla guttata have been studied by one
of my students and the results published elsewhere (Nowlin, ’06). In
both an even number of chromosomes (22, 18) was found in the sper-

MISCELLANEOUS COLEOPTERA. 45

matogonia, one being very small and forming with a larger one an
unequal pair which remained condensed during the growth stage and
separated into its larger and smaller components in the first sperma-
tocyte mitosis. The result of maturation, as in the other species here
described and in Zenxebrio molitor, is dimorphism of the spermatozoa.
The method of synapsis in Coptocycla is like that described for
Chelymorpha argus.

HEMIPTERA HOMOPTERA.
Aphrophora quadrangularis.

The abundance of Aphrophora at Harpswell, Maine, in June and
July, 1905, suggested that it might be well to examine at least one
more of the Hemiptera homoptera for comparison with the many spe-
cies of Hemiptera heteroptera which have been recently reexamined
by Wilson (’05, ’05 , 06).

The larvee only were collected, as they gave all the desired stages
fora study of the spermatogenesis, and also oogonia and synizesis
and synapsis stages of the oocytes. In the first collections the testes
were dissected out, but the many free follicles break apart so easily
that the later material was prepared by cutting out the abdominal seg-
ments which contained the reproductive organs, and fixing those
without dissection. The same methods of fixation and staining were
employed as for the Coleoptera. Hermann’ssafranin-gentian method
was especially effective with this material.

In Aphrophora the follicles of each testis are free, forming a dense
cluster, each follicle being connected with the vas deferens by a short
duct. The very young follicles are spherical, the older ones ovoid in
form. ‘The primary spermatogonia (plate xiv, fig. 237)—very clear
cells with a lobed nucleus which stains slightly—occupy the tip of
the follicle. Next to these comes a layer of cysts of secondary sperma-
togonia which are conspicuous for their deeper staining quality (fig.
238). There appears to be no plasmosome in either class of sperma-
togonia. Figure 239 is the equatorial plate of a secondary spermato-
gonium. ‘There are 23 chromosomes, two of which are conspicuously
larger than the others and evidently form a pair. The odd one is one
of the three next in size.

Next to the secondary spermatogonia are cysts of young spermato-
cytes, whose nuclei show a continuous spireme and an elongated
deeply staining chromatin rod which is the odd chromosome (fig.
240). This is often more elongated than in the figure and more or
less wormlike in appearance. A pair of smaller chromatin masses may
sometimes be detected at this stage, and are readily found a little

46 STUDIES IN SPERMATOGENESIS.

later (fig. 241) when the nucleus has enlarged and the spireme has
become looser and stains less deeply. Here the odd chromosome is
more condensed, or shortened, and split. There is no synizesis and
no polarized or bouquet stage, but the nuclei of all of the spermato-
cytes contain a continuous spireme throughout the growth stage.
Synapsis must occur at the close of the last spermatogonial mitosis
before the spireme is formed. Figures 242 and 243 show a slightly
later growth stage. The form and connection of the ‘‘#z-chromosome’’
pair (Wilson, ’05,) comes out clearly here. Figure 244, froma safranin-
gentian preparation, shows both the odd chromosome and the m-
chromosomes. Some time before the first mitosis, the spireme splits
and the pairs of granules embedded in linin are wonderfully distinct,
both in iron-hzematoxylin and safranin-gentian preparations (fig.
245). The m-chromosomes have here formed a precocious tetrad (mz).
Figure 246 is a similar stage from a safranin-gentian preparation. Fig-
ures 247 and 248 show the condensation of chromatin granules to form
tetrads of various sizes, still embedded in the linin spireme. As these
tetrads come into the spindle without losing their elongated form, it is
evident that each one consists of two longitudinally split chromo-
somes united end to end in synapsis and separated in the first matura-
tion mitosis, which is therefore reductional, The odd chromosome
and the #-chromosomes show no longitudinal split in these figures,
but they may appear as in figure 249. Occasionally one of the tetrads
takes the form ofa cross (fig. 249). In this figure the split ‘‘ acces-
sory ’’ (x) lies against the nuclear membrane and the archoplasmic
material for the spindle is seen along one side of the nucleus. It is
certain here that the spindle fibers come from extranuclear material,
not from nuclear substance, as Paulmier (’99) describes for Azasa
tristts.

Figures 250 and 251 show the first maturation mitosis as it usually
appears in sections from mercuro-nitric material stained with iron-
hematoxylin. The odd chromosome is always more or less eccentric
and is attached by a spindle fiber to one pole. In Hermann material,
considerably destained, the tetrads and the odd chromosome appear
as in figures 252, 253, and 254, the tetrads being in position for a trans-
verse division. ‘The odd chromosome is always so placed that its lon-
gitudinal split is at right angles to the axis of the spindle, as though
it were to divide in this mitosis. It does not do so, however, but
goes to one daughter cell, always lagging behind, as is shown in
figures 255 and 256. Figures 257,a and J, are polar plates of the
first mitosis with 11 and 12 chromosomes, respectively, and fig-
ures 258, a, 6, and c, show the polar plates (a and ¢c) each containing

APHROPHORA OQUADRANGULARIS. 47

11 chromosomes, and the odd chromosome at a different level (0).
The latter is a view of the anaphase which one often gets at three foci
in one section. Figures 259,a@ and 4, are equatorial plates of the sec-
ond mitosis with 11 and 12 chromosomes respectively. Figure 260
shows a side view of the second spindle in metaphase, and figure 261
in anaphase. Figures 262 and 263 are daughter plates from two
spindles showing the chromosome content of the two equal classes of
spermatozoa, one class containing 11 ordinary chromosomes, the other
Ii ordinary chromosomes plus the odd heterochromosome, for the odd
chromosome divides with the others in the second spindle as in
Orthoptera (McClung and Sutton).

In figures 264 and 265 (plate xv) are seen the telophase of the two
kinds of second spermatocytes, one (fig. 265) showing the divided odd
chromosome, which continues to stain more deeply after the others
have become diffuse. All of the spermatids (figs. 266-268) contain, in
the early stages of development, a body () which stains like chroma-
tin, but increases in size from a small granule in the telophase (figs.
264, 265) to the large dense body (7) seen in figure 267. This is prob-
ably homologous with the chromatin nucleolus described for the
spermatids of the Coleoptera. In addition to this, in one-half of the
spermatid nuclei there is a condensed mass of chromatin which is
evidently the derivative of the odd chromosome of the spermatogonia
and spermatocytes (figs. 267 and 268, x), In common with the sperm-
atids of other Hemiptera these show two masses of archoplasm, the
larger of which forms the sheath (s) of the axial fiber of the tail, and
the smaller the acrosome (a2). The axial fiber grows out directly from
the centrosome, on either side of which there is a dense band forming
the lateral boundary of the middle piece. It will be seen that the
odd chromosome of Aphrophora is in its behavior precisely like the
typical Orthopteran ‘‘ accessory ’’ of McClung, and similar to the odd
chromosome of the Coleoptera.

In various parts of the young male larve dividing cells were found
and the number 23 determined (fig. 269). Turning now to the female
larvee to determine the somatic number, the oogonia proved to be more
favorable for counting. ‘Twenty-four chromosomes were present in
equatorial plates of oogonial mitoses (fig. 270), thus confirming Wil-
son’s results for the Avzasa group of the Hemiptera heteroptera.

_ In examining sections of female larvee stained with safranin-gentian-
violet, I was surprised to see a very marked polarized or bouquet
stage and to find among the loops something resembling the odd chro-
mosome of the growing spermatocytes. It was difficult to get a clear
view of this body as it lay within the loops. In one section of a

48 STUDIES IN SPERMATOGENESIS.

slightly earlier stage before synapsis, there were found two pairs of
chromosomes (fig. 271, %,, %2, and 1, m2) which were stained with
safranin in contrast with the violet spireme. These two pairs I
interpret as being (1) the homologues of the pair of #-chromosomes,
which remain condensed during the growth stage of the spermato-
cytes, and (2)a pair of heterochromosomes corresponding to the odd
chromosome of the male. Various combinations of these heterochro-
mosomes are shown in figures 272-277. Figures 278 and 279 were
taken from mercuro-nitric material stained with iron-hematoxylin.
In section 278 the ‘‘ bouquet’’ was cut through, showing the bivalent
corresponding to the larger pair in figure 271, and in figure 279 this
element is seen behind the paler loops. The history of these two pairs
of heterochromosomes, which have not, so far as I know, been found
before in oocytes, should be followed up in older ovaries, and related
species should be examined for similar phenomena.

LEPIDOPTERA.
Cacoecia and Euvanessa.

I had no intention of making an extended study of the spermato-
genesis of the Lepidoptera, but was interested to see if anything cor-
responding to the heterochromosomes of other orders could be found.
The material studied was the testes of the larvee of Cacwcia cerasivor-
ana and Exuvanessa antiopa. 'Thenumber of chromosomes is large, but
the equatorial plates are diagrammatically clear. In’ both species 30
chromosomes are found in both first and second spermatocytes. In
both, one chromosome is larger (figs. 290 and 293, x). In the growth
stage (figs. 283, 284) there is a two-lobed body (or sometimes two sep-
arate spherical bodies) which seems to correspond in size to the larger
pair of chromosomes in the first spermatocyte. In iron-hematoxylin
preparations this pair is often obscured by parts of the spireme which
are tangled around it. In safranin-gentian preparations it stains, not
like a plasmosome, but red like the heterochromosomes, while the spi-
remeis violet. The staining reaction at least suggests that this equal
pair of chromosomes, which may be traced through the synizesis stage
(fig. 280), synapsis stage (figs. 281, 282), growth stages (figs. 283, 284),
and prophases (figs. 285-287), into the first spermatocyte spindle (figs.
288, 290), and on to the second spermatocyte (figs. 289, 291, 292), is
an equal pair of heterochromosomes comparable to the equal pair of
‘“idiochromosomes ’’ found by Wilson in Vezara (’05). As the various
stages are practically the same in Auvanessa antiopa, but somewhat
clearer in Cacecia, only one figure is given for Ezvanessa—the equa-
torial plate of the first spermatocyte (fig. 293).

SUMMARY OF RESULTS. 49

SUMMARY OF RESULTS.

(1) An unequal pair of heterochromosomes has been found by the
author in 19 species of Coleoptera belonging to 8 families :

FAMILY. SPECIES,

I. Buprestide ......... Two spruce-borers, species not determined.

{ 1. Chlentus cesttvus.
II. Carabide ............ 2. Chlenius pennsylvanicus.
| . Galertta bicolor.
. Blepharida rhots.
. Chelymorpha argus.
. Coptocycla aurichalcea.
. Coptocycla guttata.
. Doryphora decemlineata.
. Odontota dorsalis.
. Trirhabda virgata.
Trirhabda canadense.
IV: Cicindelide ......... Cicindela primeriana.

: . Adalia bipunctata.
Wee Coccinellidzeysn.-.1¢ pie Barecias.

III. Chrysomelidz ...... 4

OIANRWNH W

Wilks Scaralcetdee) s-cemess Euphoria inda.
WAU, ASiiljalouieles! oedhaceponeone Silpha americana,
VIII. Tenebrionidz........ Tenebrio molitor.

(2) An odd chromosome, which behaves during the growth stage of
the first spermatocytes like the ‘‘ accessory’’ of the Orthoptera, has
been found in 4 species of Coleoptera,* belonging to 3 families:

FAMILY. SPECIES.
il, (Cereal OG ED soscocponsucnodoc Anomoglossus emarginatus.
IQL) IBIERveseio ie shbcsuodonoscecer Two Elaters; species not determined.
Tih, Lampyridz......-..-.... LEllychnia corrusca.

(3) In most of the species of Coleoptera examined, the unequal pair
ot the odd chromosome remains condensed during the growth period
of the first spermatocyte, like the ‘‘ accessory ’’ of the Orthoptera and
the various heterochromosomes of the Hemiptera.

(4) Several of these species of Coleoptera have a synizesis stage in
which the spermatogonial number of short loops is massed at one side
of the nucleus. This is followed by a synapsis stage in which the
loops straighten and unite in pairs, forming longer loops which soon

* AUG. 20, 1906.—Since this paper was prepared, 19 other species of Coleoptera
have been studied. Of these, 17 have an unequal pair of heterochromosomes in the
spermatocytes. Six belong to the Chrysomelide, making 14 of that family that have
been examined. Representatives of 4 new families—Melandryide, Lamiinz, Mel-
oide, Cerambycinz—have been studied. In only two species,—1 Elater and 1
Lampyrid—has the odd chromosome been found in place of the unequal pair. No
species of Coleoptera has yet been examined in which one or the other of these two
types of heterochromosomes does not occur in the spermatocytes. Of the 42 species
of Coleoptera whose germ cells have been studied, 85.7 per cent are characterized by
the presence of an unequal pair of heterochromosomes in the male germ cells, 14.3
per cent by the presence of an odd chromosome,

50 STUDIES IN SPERMATOGENESIS.

spread out in the nuclear space, and, with the exception of the hete-
rochromosomes, unite to form a continuous spireme.

(5) In several of the species of Coleoptera and in Aphrophora, it
has been shown that a body staining like chromatin develops in the
spermatids, increasing in size for a time, then breaking up into gran-
ules and disappearing. This body evidently has no relation to the
heterochromosomes, as it is the same for all of the spermatids. Its
staining qualities suggest that it may be material derived from the
chromosomes. It is finally dissolved in the karyolymph.

(6) In iron-hematoxylin preparations the heterochromosomes of the
Coleoptera vary greatly in their staining properties during mitosis. In
some species they stain exactly like the ordinary chromosomes, in
others the larger one of the unequal pair holds the stain more tena-
ciously than the others and also than its smaller mate, and this is true
in several cases where the heterochromosome is smaller than the other
chromosomes, which destain more readily. The odd chromosome
of the Elaters stains less deeply than the others in the first spermato-
cyte. In the growth stage they stain more deeply, as a rule, than the
spireme, with iron-hzmatoxylin or thionin, stain red with safranin-
gentian and green with Auerbach’s methyl green-fuchsin combination.

(7) Aphrophora quadrangularis agrees with the Azasa group of
Hemiptera heteroptera in having a pair of #-chromosomes and an odd
chromosome in the spermatocytes, but differs from many of that group
in that the odd chromosome divides in the second mitosis instead of
the first. It also differs from other known forms in exhibiting hete-
rochromosomes in certain stages of the oocytes.

(8) The two species of Lepidoptera examined have an equal pair
of heterochromosomes.

COMPARISON OF RESULTS. 51

COMPARISON OF RESULTS IN DIFFERENT SPECIES OF
COLEOPTERA,

In number of chromosomes there is great variation, the’ smallest
number (16) having been found in Odontota dorsalis, and the largest
(40) in Sz/pha americana. ‘The difference in size is also very marked,
as may be seen by comparing the spermatogonial plates in figures 3
and 58 with those shown in figures 94 and 141.

No other species of the Tenebrionide has yet been secured, and all
of the other beetles examined differ in a marked degree from 7enebrio
molitor in the growth stages of the spermatocytes. While in Zenebrio
the chromatin stains very dark throughout the growth stage, and the
unequal pair can not be distinguished until the prophase of division
(05, plate vi, figs. 171-180), in most of the others there are very dis-
tinct synizesis and synapsis stages, following the last spermatogonial
mitosis, then a spireme stage in which the condensed unequal pair of
heterochromosomes or the odd chromosome is conspicuous in contrast
with the pale spireme, whether the preparation is stained with iron-
hematoxylin, gentian, or thionin. In Zenebrio molitor, the unequal
pair behaved in every respect like the other bivalent chromosomes.
In the other forms, though it behaves during the two maturation divi-
sions like the symmetrical bivalents, it remains condensed during the
growth period like the ‘‘accessory’’ of the Orthoptera, the odd
chromosome, ‘‘ m-chromosomes,’’ and ‘‘ idiochromosomes’’ of the
Hemiptera. In several cases the heterochromosomes of the Coleoptera
are associated with a plasmosome (figs. 22, 23, 63, 132, 158, 217), as
is often true in other orders. This peculiar pair of unequal hetero-
chromosomes varies considerably in size during the growth stage in
some of the species studied, but changes very little in form, differ-
ing in this respect from the ‘‘accessory’’ in some of the Orthoptera
(McClung, ’o2) and from the large idiochromosome in some of the
Hemiptera (Wilson, ’05).

The odd chromosome, so far as it has been studied, behaves pre-
cisely like the larger member of the unequal pair without its smaller
mate (figs. 219, 220, 226, 233). Inthe growth stage it remains con-
densed and either spherical or sometimes flattened against the nuclear
membrane (figs. 217, 225, 231). In the first maturation mitosis it is
attached to one pole of the spindle, does not divide, but goes to one of
the two second spermatocytes (figs. 233, 235). In the second sper-
matocyte it divides with the other chromosomes, giving two equal

classes of spermatids differing by the presence or absence of this odd
chromosome.

52 STUDIES IN SPERMATOGENESIS.

All of the evidence at hand leads to the conclusion that in the
Coleoptera, the univalent elements ofall the pairs, equal and unequal,
separate in the first spermatocyte mitosis and divide quantitatively in
the second. In this respect the behavior of the chromosomes in this
order appears to be much more uniform than in the Orthoptera and
Hemiptera.

COMPARISON OF THE COLEOPTERA WITH THE HEMIPTERA

AND LEPIDOPTERA,

As has been seen above, the conditions in the Coleoptera, so far as
the heterochromosomes are concerned, correspond very closely in final
results with those in the Hemiptera heteroptera and the Orthoptera.
In minor details these chromosomes are less peculiar in the Coleop-
tera than in either of the other orders. KEven condensation during the
growth stage is not universal, and synapsis of the heterochromosomes
apparently occurs simultaneously with that of the ordinary chromo-
somes, instead of being delayed, as in many of the Hemiptera heter-
optera.

Aphrophora (Hemiptera homoptera) agrees with the Azasa group of
the Hemiptera heteroptera in having a pair of condensed m-chromo-
somes, in the growth stage, but this pair is already united in synapsis
when first seen. It differs from Avasa, but agrees with Banasa and
Archimerus in exhibiting a typical odd chromosome which goes to
one pole without division in the first spermatocyte, and divides with
the other chromosomes in the second spermatocyte. The odd chromo-
some in this species of Hemiptera, therefore, behaves like that in the
Coleoptera and Orthoptera. The most interesting points in the results
of this study of the germ cells of Aphrophora is the discovery of two
pairs of condensed chromosomes in certain phases of the growth stages
of the odctyes. ‘This has not been shown to be the case in any other
species of Hemiptera, so far as I can ascertain. It is now evident that
in the Heteroptera homoptera there are at least two distinct classes as
to behavior of chromosomes. In one class we have the Aphids
(Stevens, ’05 and ’06) and Phylloxera (Morgan, ’06) in which no hete-
rochromosomes have been found, while in the other class are such
forms as Aphrophora with both a pair of m-chromosomes and a
typical odd heterochromosome.

The two species of Lepidoptera examined indicate that here we may
have conditions comparable to those in Mezara—an equal pair of
heterochromosomes whose only apparent peculiarity is their condensed
form during the growth stage. Doubtless the results of other investi-
gators will soon throw more light on the heterochromosomes of this
order.

GENERAL DISCUSSION. ce

GENERAL DISCUSSION.

It will be seen from the foregoing that the results obtained in the
study of the germ cells of 7exebrio molitor have been confirmed in full
for several species of Coleoptera, and in part for 19* different species
belonging to 8* families. It has also been shown that a different type
of Coleopteran spermatogenesis exists in at least 3 families, where an
odd chromosome like that in the Orthoptera occurs in place of the
unequal pair. In all of these insects the spermatozoa are distinctly
dimorphic, forming two equal classes, one of which either contains
one smaller chromosome or lacks one chromosome.

The most difficult part of the work has been the determination of
the somatic number of chromosomes in the male and female. Insome
cases suitable material has been lacking; in others, thottgh material
was abundant, no metaphases could be found in which the chromo-
somes were sufficiently separated to be counted with certainty. In
three species (in addition to Zenxebrio molitor) where the unequal pair
is present, the female somatic cells have been shown to contain the
same number of chromosomes as the spermatogonia, but an equal
pair in place of the unequal pair of the male. In two new cases the
male somatic number and size have been shown to be the same as in
the spermatogonia. In oneof the Elateride, where the spermatogonial
number is 19, the female somatic number is 20, and in Aphrophora the
numbers in male and female cells are respectively 23 and 24. No ex-
ception has been found to the rule established by previous work on
the Coleoptera (Stevens, ’05) and on the Hemiptera (Wilson, ’05 and
’06), that (1) in cases where an unequal pair is present in the male germ
cells, it is also present in the male somatic cells, but is replaced in
the female by an equal pair, each component being equal in volume
to the larger member of the unequal pair, and (2) in cases where an
odd chromosome occurs in the male, a pair of equal size are found in
the female. It is therefore evident that an egg fertilized by a sper-
matozoon (1) containing the small member of an unequal pair or
(2) lacking one chromosome, must develop into a male, while an
egg fertilized by a spermatozoon containing the larger element of an
unequal pair of heterochromosomes or the odd chromosome must
produce a female.

Whether these heterochromosomes are to be regarded as sex chro-
mosomes in the sense that they both represent sex characters and
determine sex, one can not decide without further evidence.

*AUG. 20, 1906.—36 species belonging to 12 families. See note, p. 49.

54 STUDIES IN SPERMATOGENESIS.

Comparison of the two types in Coleoptera, especially where, as in
the Carabidze, both occur in one family, has suggested to me that here
it is possible that the small chromosome represents not a degenerate
female sex chromosome, as suggested by Wilson, but some character
or characters which are correlated with the sex character in some spe-
cies and not in others. Assuming this to be the case, a pair of small
chromosomes might be subtracted from the unequal pair, leaving an
odd chromosome. ‘The two types would then be reduced to one. It
may be possible to determine the validity of this suggestion for partic-
ular cases by observation or experiment.

Since the first of this series of papers was published, there have
appeared three important papers by Prof. E.\B. Wilson, bearing on the
problem of sex determination in insects. These papers are based on
a study of many species of the Hemiptera heteroptera. These insects
fall into two classes—one in which a pair of ‘‘ idiochromosomes,’’
usually of different size, remain separate and divide quantitatively in
the first spermatocyte, conjugate and then separate in the second
maturation mitosis; and another class in which an odd chromosome—
the ‘‘ heterotropic ’’ chromosome—divides in one of the maturation
mitoses, but not in the other. Wilson regards the odd chromosome as
the equivalent of the larger of the ‘‘idiochromosomes,’’ its smaller
mate having disappeared. In the somatic cells of the former class he
finds in the male the unequal pair, in the female an equal pair, the
smaller chromosome being replaced by an equivalent of the larger
‘‘idiochromosome.’’ In the latter class the male somatic cells con-
tain the odd number, the female somatic cells and oogonia an even
number, the homologue of the odd chromosome of the male being
present and giving to the female one more chromosome than are found
in the male.

In his latest paper Wilson (’06) makes a variety of suggestions as
to sex determination. He shows that if the ‘‘idiochromosomes ’’ and
the heterotropic chromosome be regarded as sex chromosomes in the
double sense that they both bear sex characters and determine sex, the
following scheme accounts for the observed facts in all cases where
an unequal pair or an odd heterochromosome have been found:

Sperm, Egg.
Large 3 ‘‘idiochromosome "’
1% or -+ Large 9 sex chromosome=a 9
Odd chromosome.

Small 9 “‘ idiochromosome "’
8 i or + Large 3’ sex chromosome=a

No sex chromosome

GENERAL DISCUSSION. 55

Here we know that such a combination of gametes must occur to
give the observed results, but we are not certain that we have a right
to attribute the sex characters to these particular chromosomes or in
fact to any chromosomes. It seems, however, a reasonable assump-
tion in accordance with the observed conditions. The scheme also
assumes either selective fertilization or, what amounts to the same
thing, infertility of gametic unions where like sex chromosomes are
present. It also assumes that the large female sex chromosome is
dominant in the presence of the male sex chromosome, and that the
male sex chromosome is dominant in the presence of the small female
sex chromosome. Or, it might rather be said that these are not really
assumptions, but inferences as to what must be true if the heterochro-
mosomes are sex chromosomes. ‘This theory of sex determination
brings the facts observed in regard to the heterochromosomes under
Castle’s modification of Mendel’s Law of Heredity (’99).

The question of dominance is a difficult one, especially in parthe-
nogenetic eggs and eggs which are distinctly male or female before
fertilization. It may be possible that the sex character of the egg after
maturation is always dominant in the fertilized egg, as appears to be
the case in these insects (see scheme). Conditions external to the
chromosomes may determine in certain cases, such as Dinophilus,
which sex character shall dominate in the growing oocyte, and matu-
ration occur accordingly. It is evident that this reasoning would lead
to the conclusion that sex is or may be determined in the egg before
fertilization, and that selective fertilization, or infertility of gametic
unions containing like sex characters, has to do, not with actual sex
determination, but with suitable distribution of the sex characters to
future generations. If both sex characters are present in parthenoge-
netic eggs, as appears to be the case in aphids and phylloxera, domi-
nance of one or the other must be determined by conditions external
to the chromosomes, for we have both sexes at different points in the
same line of descent without either reduction or fertilization.

Wilson suggests as alternatives to the chromosome sex determinant
theory according to Mendel’s Law, (1) that the heterochromosomes
may merely transmit sex characters, sex being determined by proto-
plasmic conditions external to the chromosomes; (2) That the hetero-
chromosomes may be sex-determining factors only by virtue of dif-
ference in activity or amount of chromatin, the female sex chromosome
in the male being less active. The first of these alternatives is an
attempt to cover such cases as Dinophilus, Hydatina, and Phylloxera
with large female and small male eggs. Here Morgan’s (’06) sugges-
tion as to degenerate males seems much to the point. The male sex

56 STUDIES IN SPERMATOGENESIS.

character, having become dominant in certain eggs at an early stage,
may, from that time on, determine the kind of development. As to
the second alternative, I see no reason for supposing that the small
heterochromosome of a pair is in any different condition, as to activity,
from the large one. ‘The condensed condition may not mean inactiv-
ity, but some special form of activity. And, moreover, it has been
shown that in certain stages of the development of the oocyte of one
form, Aphrophora quadrangularis, there are pairs of condensed chro-
mosomes corresponding to those of the spermatocyte, so that there
would hardly seem to be any basis for Wilson’s attempt to associate
the difference in development of male and female germ cells with
activity or inactivity of chromosomes, as indicated by condensed or
diffuse condition of the chromatin.

On the whole, the first theory, which brings the sex determination
question under Mendel’s Law ina modified form, seems mostin accord-
ance with the facts, and makes one hopeful that in the near future it
may be possible to formulate a general theory of sex determination.

This work has been done in connection with a study of the problem
of sex determination, but, whatever may be the final decision on that
question, it brings together a mass of evidence in favor of the belief in
both morphological and physiological individuality of the chromo-
somes, as advocated by Boveri, Sutton, and Montgomery. It also
gives the strongest kind of evidence that maternal and paternal homo-
logues unite in synapsis and separate in maturation, leaving the ripe
germ cells pure with regard to each pair of characters.

BRYN MAwR COLLEGE, /une 7, 1906.

BIBLIOGRAPHY. CY

BIBLIOGRAPHY.

Boveri, TH.
‘02. Ueber mehrpolige Mitosen als Mittel zur Analyse des Zellkerns. Verh. d.
phys.-med. Ges. Wiirzburg, N. F., vol. 35.
CasTLeE, W. E.
03. The heredity of sex. Bull. Mus. Comp. Zodl. Harvard College, vol. 40,
no. 4.
McCuuna, C. E.
‘99. A peculiar nuclear element in the male reproductive cells of insects. Zodl.
Bull., vol. 2. .
‘oo. The spermatocyte divisions of the Acridiidae. Kans. Univ. Quart., vol. 9,
ial itn
‘or. Notes on the accessory chromosome. Anat. Anz., vol. 20, nos. 8 and 9.
‘oz. The accessory chromosome—sex-determinant? Biol. Bull., vol. 3, nos. 1

and 2.

‘o2a. The spermatocyte divisions of the Locustide. Kans. Univ. Quart., vol. 1,
no. 8.

05. The chromosome complex of orthopteran spermatocytes. Biol. Bull., vol. 9,
no. 5.

MontGomery, TuHos. H., Jr.
‘or. A study of the chromosomes of the germ-cells of Metazoa. Trans. Amer.
IPlowil, Sleek, Wells Aoy
‘03. The heterotypic maturation mitosis in Amphibia and its general significance.
Biol. Bull., vol. 4, no. 5.
‘ora. Further studies on the chromosomes of the Hemiptera heteroptera. Proc.
Acad. Nat. Sci. Phila., rgor.
‘04. Some observations and considerations upon the maturation phenomena of
the germ-cells. Biol. Bull., vol. 6, no. 3.
'05. The spermatogenesis of Syrbuda and Lycose and general considerations upon
chromosome reduction and heterochromosomes. Proc. Acad. Nat. Sci.
Phila., 1905.
Morean, T. H.
‘06. The male and female eggs of Phylloxerans of the Hickories. Biol. Bull., vol.
IO, NO. 5.
Now tin, W.N.
’06. A study of the spermatogenesis of Coftocycla aurichalcea and Cofptocycla
guttata. Journ. of Exp. Zodl., vol. 3, no. 3.
PAuULMIER, F. C.
‘99. The spermatogenesis of Anasa tristzs. Journ. of Morph., vol. 15.
DE SINETY. ;
‘or. Recherches sur la biologie et 1’anatomie des phasms. La Cellule, vol. 19.
STEVENS, N. M.
'o5. A study of the germ cells of Aphis rose and Aphis enothere. Journ. of
Exp. Zo6l., vol. 2, no. 3. ii
‘o5a. Studies in spermatogenesis, with especial reference to the ““ accessory
chromosome.’’ Carnegie Inst. of Wash., pub. no. 36.
‘06. Studies on the germ cell of Aphids. Ibid., pub. no. 51.

58 STUDIES IN SPERMATOGENESIS.

SuTTON, W. S.

’o2. On the morphology of the chromosome groupin Srachystola magna. Biol
Bull., vol. 4, no. 1.

'03. The chromosomes in heredity.

Biol. Bull., vol. 4, no. 5.
WI ison, E. B.

'o5. Studies on chromosomes. I. The behavior of the idiochromosomes in

Hemiptera. Journ. Exp. Zool., vol. 2, no. 3.
‘osa. The chromosomes in relation to the determination of sex in insects.
Science, vol. 22, no. 564.

’o5d. Studies on chromosomes. II. The paired microchromosomes, idiochro-
mosomes, and heterotropic chromosomes in Hemiptera.
Zool., vol. 2, no. 4.

‘06. Studies on chromosomes. III.

Journ. Exp.

The sexual differences of the chromosome-
groups in Hemiptera, with some considerations of the determination and
inheritance of sex. Ibid., vol. 3, no. I.

60

DESCRIPTION OF PLATES.

[The figures were all drawn with Zeiss oil-immersion 2mm., oc. 12, and have been
reduced one-third, giving a magnification of 1,000 diameters. ]

PiaTe VIII.
_Trirhabda virgata (Family Chrysomelide).

Equatorial plate from somatic tissues of a male pupa, 27 large chromosomes,
I small one. .

. Equatorial plate from an egg follicle, 28 large chromosomes.

. Equatorial plate of spermatogonium, 27 large chromosomes, 1 small one.

. First spermatocyte, synizesis stage.

. First spermatocyte, early spireme stage, showing unequal pair of chromo-

somes.

. First spermatocyte, later growth stages.

8. First spermatocyte, prophase.

. First spermatocyte, metaphase.

. First spermatocyte, equatorial plate.

. First spermatocyte, anaphase, showing separation of the elements of the

unequal pair (Zand s).

. First spermatocyte, daughter plates.

. Second spermatocytes, equatorial plates.
. Second spermatocytes, equatorial plates showing V-shaped chromosomes.
. Second spermatocyte, early anaphase, the small chromosome in metakinesis.

Tritrhabda canadense.

. Equatorial plate from egg follicle, 30 large chromosomes.
. Equatorial plate of spermatogonium, 29 large chromosomes, 1 small one.
. First spermatocyte, growth stage showing the heterochromosome group.

24-27.
. First spermatocyte, equatorial plate.
. First spermatocyte, equatorial plate, small member of the unequal pair only

32733:

Heterochromosome group. #= plasmosome, /= large heterochromosome,
s = small heterochromosome.
First spermatocyte, metaphase.

present.

. First spermatocyte, daughter plates.
. Second spermatocytes, equatorial plates.

Second spermatocytes, prophase.

STEVENS

WF q
34 24

Fan,
cs ane

~

25.
xe Sse
®
(ete
N. M. S. del.

,
I2.

17.

ST.

«®
ee As

27.

COLEOPTERA

PLATE Vill.

9. 10.
b ie
e @ ® l S -.- J \ ]
: Q os
wl? @0e,
74. 15.
ah 8
es a= Ie nme
e Cr + 855
whe an ‘
a 78, b 79.
g
@ L
f) ét
23.
24.
&
C}->4
ns
2@ @®
28, Ze
i)
Seo te
@ Ss
"?

ao fae.

ee

ch
G 4)
s i
7 i=
a ee :
Z
tit
a
‘ae
uj
ope
7 é ee
- 7
*
aN?
y ;
4 i
ii *
’ - ‘
ov A
2
fs 4
: +
1 :
‘
++
P ‘
‘ .
~
‘
‘
.

as
‘i

_ a a Pe i

62

FIGS. 34-35.

DESCRIPTION OF PLATES.

PuaTeE IX.
Chelymorpha argus (Family Chrysomelide).

Equatorial plates from egg follicles, 11 equal pairs, no small chromosome.

. Equatorial plate of spermatogonium, 21 large chromosomes, I small one.

First spermatocyte, synizesis stage.

. First spermatocyte, synapsis stage.
. First spermatocyte, bouquet stage after synapsis.
. First spermatocyte, spireme stage showing the unequal pair of hetero-

chromosomes.

. First spermatocyte, prophase.

. First spermatocyte, metaphase.

. First spermatocyte, equatorial plates, x the heterochromosome pair.
. First spermatocyte, showing metakinesis of the unequal pair.

. First spermatocyte, anaphase.

. Second spermatocyte, equatorial plates.

. Second spermatocyte, anaphase.

Odontota dorsalis (Family Chrysomelide).

. Equatorial plate of male somatic cell from walls of the testis, 15 large

chromosomes, I small one.

. Equatorial plates of spermatogonia, 15 large chromosomes, I small one.
. Resting nucleus of spermatogonium, showing plasmosome (P).

. First spermatocyte, synizesis stage.

. First spermatocyte, synapsis stage.

. First spermatocyte, spireme stage, showing the larger and smaller hete-

rochromosome associated with a plasmosome.

. First spermatocyte, prophases.

STEVENS

N. M. S. del.

, Z
Se: Dine
a ao aac ~

a 30.

41.

47. 4.

60.

PLATE IX

\
On ih’
77. 8 39:
“A V2 °
43+ 44. 45.
of: eec8e
; ene ry i
mw Ne

49»

55:
56 A
3
v
)
P Wi ili}
p 6 63
ol.
Qo ©
cs
=.

66.

COLEOPTERA

64

Fics. 69-70.
71.
Wie

73-74:
75-76.
77:
78.

79-80.
81-87.

88.
89-90.

gl.
g2.

93:

94:

95-
96-97.
98.
99-100.
Iol.
102.

103.
IO4.
105-106.

107.

108.
I0Q.

DESCRIPTION OF PLATES.

ESN OG
Odontota dorsalis.

First spermatocyte, metaphase.

First spermatocyte, equatorial plate.

First spermatocyte, metaphase, showing metakinesis of the heterochro-
mosomes.

First spermatocyte, anaphase.

Second spermatocyte, equatorial plates.

Second spermatocyte, showing metakinesis of the small chromosome (s).

Second spermatocyte, prophase, showing chromosomes longitudinally
split.

Young spermatids, 7 the chromatin nucleolus.

A series of Stagesin the development of the sperm head, showing the
various phases in the history of the chromatin nucleolus (7).

Cross-sections of nearly mature sperm heads.

Equatorial plates of spermatogonia of abnormal individual, 15 large
chromosomes, 2 small ones.

First spermatocyte from same testis, spireme stage, showing 2 small
chromosomes associated with 1 large one and a plasmosome.

First spermatocyte from the same testis, metaphase showing a similar
heterochromosome group.

Second spermatocyte from same testis, equatorial plate, showing 2 small
chromosomes.

Efpilachna borealis (Family Coccinellide).

Equatorial plate of spermatogonium, 17 large chromosomes and 1 small
one.

First spermatocyte, spireme stage, showing the unequal pair.

First spermatocyte, late prophases.

First spermatocyte, metaphase, showing chromosomes of different forms.

First spermatocyte, equatorial plate.

Unequal heterochromosome pair from a metaphase.

First spermatocyte, anaphase; ordinary chromosomes stippled to show
more clearly the metakinesis of the unequal pair.

Second spermatocyte, equatorial plates.

Second spermatocyte, prophase.

Abnormal giant spermatids, probably in process of degeneration.

Euphoria inda (Family Scarabeide).

Equatorial plate of spermatogonium, 20 chromosomes. The 2 smallest
are the unequal pair of heterochromosomes (/ and s).

Resting spermatogonium, showing plasmosome ().

First spermatocyte, spireme stage.

STEVENS

58.

IOS.

N. M. S. del.

706,

@ %
deh
SOE
e
@,ee
71.
lid 73
‘yen
78.
79.
nN A \
) | |
a ae ‘ : / } n
iS | in,
| 4 a
\|
| \| \
8 | |
es 34. } 85. |

gl. oe
sit
@
2 06, ;
2 97
pe-n= tame S
x4 a?
2 Q= Fit
. Saf di sy a 29
Mg 103 6
IOI. eae
+e
wee l guet® o
ee x he % ae
SLY dd (4 ‘SO-PasA 1. p
ry Ams re ah? 3
og tel 3 Ar 3
Fre axt
107 108.

COLEOPTERA

PEATE

74:
.
30,
¢--%,
+-4t,
f
86.

IO4.

x.

Se r aed <M ; ,
A bd ) o- a) , 2 2 Y
os . ae ure lg » mad ¢* “ : ¢ Y ~ ae : \ de meres
i ‘ in watt ~ “toy Pea ¥ ie ' 2 : is ‘
7 a nl *
iy ca fe) 4 } ; v
iv ww
ym Ay '
a a , Jus ” .
a ;
4 Fd ea i 4
a(t Ries .
vy o ‘ ;
fo > 2) ? 7 4 ‘
bd tT : ,
r . d
id 4
é
ps =
ry 1
4 °
1s
,
i
A)
an
Ye
:
i
.
’
i
*
-
.
‘
‘

66

Fics. 110-111.
112-113.
I14-116.

117.
I18-120.
Tin
1225
I23.
I24-125.
126-127.
128-130.

131-132.

133-135.
136.
Tia 7e

138.
139-140.

I4I.

142.
143-144:
145.
146-147.
148.
149.
150.

DESCRIPTION OF PLATES.

PLaTE XI.
Euphoria inda.

First spermatocyte, prophases.

First spermatocyte, late prophase.

First spermatocyte, metaphase.

First spermatocyte, equatorial plate, x the unequal pair.
First spermatocyte, anaphase.

First spermatocyte, daughter plates.

Second spermatocyte, prophase.

Second spermatocyte, equatorial plates.

Second spermatocyte, daughter plates of the two classes.
Second spermatocyte, anaphase.

Spermatids, 2 the chromatin nucleolus.

Blepharida rhots (Family Chrysomelide).

First spermatocyte, spireme stages, showing the heterochromosome
group.

First spermatocyte, beginning.of metakinesis.

First spermatocyte, equatorial plate, x the unequal pair.

First spermatocyte, late anaphase, showing the heterochromosomes 7/
and s.

Second spermatocyte, equatorial plates.

Second spermatocyte, daughter plates of the two classes.

Silpha americana (Family Silphide).

Equatorial plate of spermatogonium, 40 chromosomes—39 large, 1
small. ;

Resting nucleus of spermatogonium, showing 2 plasmosomes ().

First spermatocyte, spireme stage.

First spermatocyte, prophase.

First spermatocyte, metaphase.

First spermatocyte, equatorial plate.

Second spermatocyte, equatorial plates.

Second spermatocyte, showing metakinesis of the small chromosome.

STEVENS

N. M. S. del.

142,

~,) @
6% af
123
a ——
128,
ae
7@ e
134.
ome «3 o
oe ° sere
ip

I4}.

rms. 179.
&
Ne PS
WSS vy
a@ 124. 2)
I -+---@ id ae
129.
730.

I 35.

COLEOPTERA

PLATE

fe

3 38

68

FIGS. I51-152.
153:
154.
155-158.

159.
160-163.
164-171.

172.
173-174-
175-176.

I77-
178-179.
180-186.

187.
188-1809.

Igo.
IgI.

192.

DESCRIPTION OF PLATES.

PLATE XII.
Doryphora decemlineata (Family Chrysomelide).

Equatorial plates of spermatogonia, 36 chromosomes—35 large, 1 small.

First spermatocyte, synizesis stage.

First spermatocyte, synapsis stage.

First spermatocyte, spireme stages.

First spermatocyte, spireme segmented and split.

First spermatocyte, prophases.

First spermatocyte, metaphase.

First spermatocyte, anaphase.

First spermatocyte, equatorial plates.

First spermatocyte, late anaphase.

Second spermatocyte, equatorial plates.

Second spermatocyte, telophase, a, archoplasmic material.

Spermatids in different stages; a1, archoplasmic material from first
spermatocyte spindle, az archoplasmic material from second matu-
ration spindle.

Spruce-borers (Family Buprestidae).

First spermatocyte, metaphase.

First spermatocyte, equatorial plates of two species, ro and 11 chro-
mosomes.

First spermatocyte, anaphase.

Second spermatocyte, equatorial plates containing 9 large chromo-
somes and 1 small one.

Chromosomes from prophase of the first spermatocyte, all from the
same Cyst.

STEVENS

I57.

769.

787.

N. M. S. del.

Jyu
~
SAWS
0 2
o(=
-_ « & S
NifA
3
252 453 154.
*
dS ~-
= f
an a 160.
158. oe

iy it

165. =
166
om f f
Wh sis x
yey
‘ : 172
170. HIE 7
Ae
eres @
Vie
»)
Tie b
ie a,
\ J
I8I 82. f
183.
@.», @ ®
@e
@ o° : ®e AY of
e 2 eee
e® ois oe
" ®
188, 789.
i rgl.
790.

COLEOPTERA

@..x

PLATE XII.

7O

Fic. 193.
194.
IQ5-
196.
T1972

198.
199.
200.
201.
202.
203.
204.
205.

206.

207.

208.
209-210.
211.
212.

213.
214.
215.

216.

217
218.
219-220.
221.
222.

223.

224.
225.
226.
227.
228.
229.

230.
231.
232.
233-
234.
235.

236.

DESCRIPTION OF PLATES.

PLaTeE XIII.
Adalia bipunctata (Family Coccinellide).

Equatorial plate of spermatogonium, 20 chromosomes—rg large, 1 small.
First spermatocyte, spireme stage, x the heterochromosome group.

First spermatocyte, metaphase.

First spermatocyte, equatorial plate.

Second spermatocyte, equatorial plates.

Cicindela primeriana (Family Cicindelide).

Equatorial plate of spermatogonium, 20 chromosomes—1g large, 1 small.

First spermatocyte, spireme stage, x the heterochromosome group.

First spermatocyte, prophase.

First spermatocyte, metaphase, x the unequal pair in tripartite form.

First spermatocyte, showing metakinesis of the heterochromosomes (/ ands).

First spermatocyte, equatorial plate.

Second spermatocyte, equatorial plates.

Giant spermatocyte, spireme stage, heterochromosome group double the
usual size.

Giant spermatocyte, prophase.

Chlenius estivus (Family Carabidae).

First spermatocyte, spireme stage, showing the unequal pair associated
with a large plasmosome.

First spermatocyte, metaphase.

First spermatocyte, beginning of metakinesis.

First spermatocyte, equatorial plate, 17 chromosomes.

First spermatocyte, anaphase, showing elongated centrosome and diver-
ging univalent chromosomes.

Chlenius pennsylvanicus.

First spermatocyte, spireme stage.
First spermatocyte, equatorial plate, x the unequal bivalent.
First spermatocyte, late prophase.

Galerita bicolor (Family Carabidae).
Equatorial plate of spermatogonium, 30 chromosomes—zg9 large, 1 small.

Anomoglossus emarginatus (Family Carabide).

First spermatocyte, growth stage, x the odd chromosome.

First spermatocyte, prophase.

First spermatocytes, metaphase, x the odd chromosome.

First spermatocyte, equatorial plate.

First spermatocyte, daughter plates containing 18 and 19 chromosomes,
respectively.

Second spermatocytes, equatorial plates.

Elater I (Family Elateride, species not determined).

Equatorial plate of spermatogonium, 19 chromosomes, x the odd one.

First spermatocyte, spireme stage, x the odd chromosome.

First spermatocyte, metaphase.

First spermatocyte, prophase.

First spermatocyte, equatorial plate.

Equatorial plate from egg follicle, 20 chromosomes, x; and xg the pair
corresponding to x in the spermatogonium.

Elater IT (Species not determined).

Equatorial plate of spermatogonium, 19 chromosomes, x the odd one.
First spermatocyte, spireme stage.

First spermatocyte, prophase.

First spermatocyte, beginning of metakinesis.

‘First spermatocyte, equatorial plate, « the odd chromosome.

A pair of second spermatocytes in metaphase, two chromosomes connected,
x the odd chromosome.

Ellychniacorrusca (Family Lampyride).

Equatorial plate of spermatogonium, 19 chromosomes.

PLATE Xill.

STEVENS
vy, ; = ew
a ee e e
Ba pie » ¢ sires o
* jae pn 3 a
TN 944 : i Mgt
196. 2197:
193. 194. ee 198 oe
LY | Hol : ba
. < 20%! ones
Se. # mA ass ie é 0
e . 5
203. 204.
AaeE . . -
207, 202, 208)
BD f , -
fe. & ® owe
beh Oo } ® r) 200?
oes e alse s88gg° wag She: a
e F
; ‘ 211
2 209. 270.
20 ae ie 09
es
i) ' | we
eoee* e ‘ Pee ’ ote
: e ! e \ bor? ee .s .
ad pas = Ae aS ae nee d
A HR : é
op e
212 273. 214. > os ,
2 aie 278.
AN < s * ‘ e
6, 00 ee ee -
: feet 1 eee : ° TY) © e oes et @* . e ve ° SS ie wots a\ Ss i]
x) ee? OAs Oraten. in70 Weer
. ee e CAC Oy J aoe
221 e eg : .
a 222 6
; 220. 22 ae
219.
2 le t-—@. ah ¢ * ic
<3 et L x) oo (t awl .
AS : @ @o fee. SS A
bm iPS eo PS & ‘
Ars @o- 2 NAF = of
i & 2 onic
xi ts 228, 229. © 230,
227,
226.
*e Fo 04 Aen PY 9 9 Seta!
0,08 2 S @ x Sy
e AN af oF ?e
Fe bad ae : Ht==>- a ( { "Re Se
cs ce ‘ 234. 236
233 a 235. 3} .
N. M. S. del.

COLEOPTERA

i

72

Fic. 237.
238.

239.
240.
241-243.

244.
245.

246.
247-248.

249.
250-251.

252-254.

255-
256.
257-

258.

259.
260.
261.
262-263.

DESCRIPTION OF PLATES.

PLATE XIV.
Aphrophora quadrangularis (Hemiptera homofptera).

Resting primary spermatogonium with lobed nucleus.

Resting secondary spermatogonium, with nucleus staining much more
deeply.

Equatorial plate of secondary spermatogonium, 23 chromosomes.

First spermatocytes, very early growth stage, x the odd chromosome.

First spermatocyte, later spireme stages, showing the odd chromosome (x)
and a pair of 72-chromosomes (772).

Similar stage from a safranin-gentian preparation.

First spermatocyte, split-spireme stage, x the odd chromosome, m the m-
chromosome tetrad.

Similar stage from a safranin-gentian preparation.

First spermatocyte, condensation of chromatin granules to form tetrads in
the linin spireme.

Later tetrad stage.

First spermatocytes, metaphase from mercuro-nitric material.

Similar stages from Hermann material, showing longitudinal split in both
the bivalents, and the odd chromosome (x).

First spermatocyte, anaphase.

First spermatocyte, telophase.

First spermatocyte, daughter plates containing 11 and 12 chromosomes,
respectively.

First spermatocyte, a andc daughter plates, each containing 11 chromo-
somes, x the odd chromosome at a different level (0).

Second spermatocyte, equatorial plates of the two classes.

Second spermatocyte, metaphase.

Second spermatocyte, anaphase.

Second spermatocyte, daughter plates of the two classes.

PLATE XIV.

STEVENS
=
Sis ye Se
Let Cf
gosto’ f C 6 “A "Mm
Ve id a OP ;
f ‘ 241.
237 238. 239. Pn
- x. 5
eee M---q m _ Z
- =s im ve
244s
242. 243
<ntee. ~.@ k eo .*
~O yrs meee a e2@e
nm 9y 8 fret as fete Core
+ mM .-- i |
“s er 4 S"-@ a Bs es
BA Z Sees
wae er
247» 248. 249 En ae
) OE&
_—« ie
e ie, ©" =
i} 8g wy we Qe
“qe “nun eB x ao « ye
2
2 wt
252 253. : +
5. oop. 255. 4 es
% ® ry B e® oe e @ 2e ea?
SOM SS SP
e b @ 4
a 3} a c
257. 258. a Bye :
Kae ee e
& ete 2a
eose 8680 % oe ose
esse re “03 eBoe
oreo ‘ 262. t a 263 6
260. 261.

N. M. 8. del.
HEMIPTERA HOMOPTERA

>» : ~~
at eae Sa ae
is

74

Fics. 264-265.

266.
267-268.

260.
270.
ZY fit

272-277.

278-279.

280.

281-282.
283-284.

285.
286-287.

288.
289.
290.
291-202.

293.

DESCRIPTION OF PLATES.

PLATE XV.
Aphrophora quadrangularis.

Second spermatocyte, telophase, showing chromatin nucleolus (7)
and the products of division of the odd chromosome (x).

A spermatid containing the chromatin nucleolus (7).

Spermatids containing both the chromatin nucleolus (”) and the odd
chromosome (x), a the acrosome.

Equatorial plate from asomatic cell of a male larva, 23 chromosomes.

Equatorial plate of an odgonium, 24 chromosomes.

Resting nucleus of a young odcyte before synapsis, showing two pairs
of condensed chromosomes, corresponding in size to the m-chromo-
somes and the odd chromosome of the spermatocytes.

Sections of nuclei of odcytes, showing one or more of these hetero-
chromosomes, from safranin-gentian preparations.

Bouquet stage from iron-hzematoxylin preparations, showing the
heterochromosome bivalent (<x).

Cacecia cerasivorana (Lepidoptera).

First spermatocyte, synizesis stage, showing 2 condensed chromo-
somes (x; and %).

First spermatocyte, synapsis stage.

First spermatocyte, growth stages.

First spermatocyte, prophase.

First spermatocyte, later prophases, showing the heterochromosome
pair (x).

First spermatocyte, metaphase.

Second spermatocyte, metaphase.

First spermatocyte, equatorial plate.

Second spermatocyte, equatorial plates.

Euvanessa antiopa (Lepidoptera).

First spermatocyte, equatorial plate.

STEVENS

279.

2) -

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Ry Wate
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HEMIPTERA AND LEPIDOPTERA

268,

PLATE

278,

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287.

XV.

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