60 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
observations on tlie reducing divisions. In the germinal vesicle six 
chromatin loops arise by transverse division, and another division raises 
their number to twelve. Then follows a double longitudinal cleavage, 
with the result that twelve tetrapartite chromosomes form the equatorial 
plate of the first directive spindle, in the male and female pronuclei 
6 chromatin loops arise by transverse division, another division raises 
their number to 12, a single longitudinal division follows, and thus 21 
bipartite chromosomes form the equatorial plate of the first segmenta- 
tion spindle. In the segmentation nuclei, it is likely that 6 loops arise 
by transverse division, and two subsequent divisions increase the number 
to 12 and then to 21. A longitudinal cleavage follows. The result is 
that there are 21 bipartite chromosomes in the equatorial plate of the 
spindle. 
The Genus Apus.* — Dr. F. Braem describes a new species of Apus 
from Syria, and has made the study of this form an occasion for revising 
the other species of the genus. He begins with Brauer’s Lepidurus 
Grubei and shows that an exaggerated appreciation of minutiae has compli- 
cated the taxonomy beyond endurance. We need not go into details ; 
the point is that the systematists seem to have forgotten that distinct 
species must be established on account of differences greater than 
those which may occur between the members of a family. Of Apus 
productus the author recognizes two varieties, var. Scbafferi (Regens- 
burg, Wien, Berlin, Breslau, Konigsberg, &c.), and (?) var. glacialis 
Kroyer (Greenland). Distinct from these are the varieties Sieboldii 
(Rouen) LubbocTci (Sicily), Dayi (Syria), Middendorjii (Kiew), which 
are united by Braem in Apus extensus n. sp. He also deals with Apus 
cancriformis, A. numidicus , and A. sudanicus. 
Vermes. 
a. Annelida- 
Researches on Syllideee.t — Dr. A. Malaquin has a monograph on these 
Worms, which he arranges in four groups — 1, Exogones, e.g. Exogone ; 
2, Euxj Hides, e.g. Syllides ; 3, Syllides, e.g. Syllis , and 4, Autelytes, 
e.g. Autolytus. The cuticle, which is generally delicate, is thick in the 
Syllides ; various forms of glandular cells are to be found in the 
epidermis ; the muscles of the body-wall are always arranged in very 
simple bundles, as in the Archiannelida, and are never pennate. 
The brain has no limiting membi ane, and there is no sharp demarcation 
between the nervous and epidermal elements ; the medullary substance 
contains several masses or centres, and the oesophageal connectives are 
always superficial or lie in the epidermis. The ventral medulla is 
formed of one median and two lateral cords, and is nearly always in 
contact, by its ventral surface, with the epidermis ; in Syllis it is, 
indeed, removed from it, but is still connected by a pedicel. There are 
typically two pairs of eyes, the development of which shows that the 
different layers which compose the eye arise from the differentiation of 
a single layer of cells. Whatever be their degree of development, and 
there is in this considerable variation, the eyes are always formed of 
* Zeitschr. f. wiss. Zool., lvi. (1893) pp. 165-87 (1 pi.). 
f Lille, 1893, 8vo, 477 pp., 14 pis. From Mem. Soc. Sei. Lille. 
