278 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Spermatogenesis in Pentatoma.* — Dr. T. H. Montgomery, junr., 
lias studied the spermatogenesis up to the formation of the spermatid in 
an insect belonging to the old genus Pentatoma (Hemiptera heteroptera). 
He describes (1) the spermatogonia aud their mitoses; (2) the first 
spermatocytes from the anaphases to the rest stage ; and (3) the sper- 
matocytic mitoses. 
The resting spermatogonia are grouped in the form of rosettes, their 
cell bodies connected at the centre. In the cytoplasm, at some distance 
from the nucleus, lies a spherical idiozome, within which centrosomes 
could not be found in the resting cell. 
In the prophase of spermatogonic mitosis, the continuous chromatin 
thread segments into 14 chromosomes, which are at first elongate, and 
later nearly spherical. In the meantime a pair of centrosomes appears 
in the idiozome, then leaves the idiozome and wanders towards the 
nucleus ; the centrosomes are connected by a central spindle. The 
central spindle and pole fibres are of cytoplasmic origin, while the 
mantle fibres are probably to a great extent derived from the nuclear 
lining. The idiozome substance appears to take no part in forming 
the spindle fibres, some of it being still present in mitosis. The chro- 
mosomes are grouped in a dense plate in the monaster stage, the mantle 
fibres being attached to each end of each chromosome. 
In the rnetakinesis the 14 nearly spherical chromosomes are halved, 
but it could not be determined with certainty whether this is a longitu- 
dinal division. Fourteen daughter chromosomes pass into each daughter 
cell (first spermatocyte), and shortly afterwards the complete separation 
of these cells takes place. In the metaphase the chromosomes do not 
fuse together. The connective fibres formed in metakinesis represent 
each a hollow cylinder of linin formed from the linin of the chromo- 
somes. 
The anaphase of the first spermatocytes may be subdivided into three 
well-marked periods : the early anaphase, the synapsis, and the post 
synapsis. In the first the 14 chromosomes elongate into threads, one of 
which becomes the chromatin nucleolus. 
In the synapsis the chromosomes are closely grouped near the 
centre ; the chromatin nucleolus shortens and thickens ; a true nucleolus 
first appears closely apposed to the inner surface of the nuclear mem- 
brane, so that it is probably cytoplasmic in origin ; the idiozome forms 
a compact mass at one point on the outer surface of the nuclear mem- 
brane ; in it may be found with great regularity one or two small 
grannies, which are probably centrosomes. 
In the post synapsis the chromosomes separate as long nearly smooth 
threads, usually three or four in number, probably formed by end-to-end 
coalescence of the 13 chromosomes of the synapsis. The true nucleolus 
gradually becomes detached from the nuclear membrane ; the chromatin 
nucleolus becomes spherical, and sometimes divides into two or more 
portions. 
The telophase is characterised by the shortening and thickening of 
the chromosomes, now irregularly monilated. The true nucleolus in- 
creases in size and wanders towards the centre of the nucleus : the now 
spherical chromatin nucleolus is apposed to the nuclear membrane. The 
* Zool. Jalirb., xii. (1898) pp. 1-88 (5 pis. and 1 fig,). 
