550 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Generative and Embryonic Mitoses.* — Dr. Y. Haecker continues 
his studies on the behaviour and numerical relations of the chromosomes 
in mitosis. He believes that the chromatin substance of the nucleus 
has the tendency before each division to become by segmentation a 
characteristic number of idants constant for the species. In large nuclei 
rich in chromatin, such as occur during cleavage and development, the 
last segmentation of the threads tends to be omitted, so that bivalent 
elements are present. This suppression or imperfection of the last 
chromatin-segmentation is a wide-spread phenomenon in the life-cycle 
of generative cells (pluri valent divisions). Tn this way the quadruple 
groups in maturation-divisions are to be regarded as longitudinally cleft 
double elements. He gives a table from which the following is con- 
densed : — 
Non-generative Mitoses. 
Generative Mitoses. 
Small to medium- 
sized nuclei, with 
small chromatin 
elements. 
Medium-sized to large 
nuclei, with large 
chromatin elements 
Somatic mitoses, with the 
normal number of ele- 
ments. 
Embryonic mitoses, with 
the normal number of 
elements. 
Embryonic mitoses, with 
half the normal number 
of elements (cf. vom 
Rath. 
Mitoses in the germinal zone of 
Ascaris, in which the chro- 
matin loops break up. 
First division of maturation.^ 
(The chromatin threads 
occur in normal number, 
but closely associated in 
pairs.) 
Primitive genital cells of 
Cyclops. (The chromatin 
elements at first in pairs, 
but separate in the dy- 
aster.) 
Heterotypical and homoo- 
typical divisions in testes 
of salamander. (The union 
in pairs persists even in 
the dyaster ?) 
Generative divisions in As- 
cciris. (More than two 
elements of a lower order 
remain united ?) 
Histology and Histogenesis of Striped Muscle. j — Dr. J. Schaffer 
begins with a discussion of Colmlieim’s areas, passes to the structural 
and optical differences in fully grown muscles, contrasts this with 
adolescent and embryonic muscle, and ends with a discussion of sarco- 
lysis. 
The areas seen on a cross section of striped muscle fibres express a 
structural character of the living fibres, due to the disposition of the 
fibrillar and connective substance. The fibrils may be uniformly dis- 
posed in uniform sarcoplasm, or several fibrils may be united in pillars 
* Arch. f. Mikr. Anat., xliii. (1894) pp. 759-87 (1 pi., 2 figs.), 
f SSB. K. Akad. Wiss. Wien, cii. Abtli. iii. (1893) pp. 1-148 (6 pis.). 
