628 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
the list nine new species from South Africa and Madagascar. Six of 
these came from Prof. Weber’s collection, and three from that of Dr. H. 
Lenz. All are fully described, and their systematic position discussed. 
e. Crustacea. 
Minute Structure of Gills.* — Dr. J. Kimus has studied the gills in 
species of Asellus, Cirolana , Idotea, Anilocra , and Cymothoa. Each lamella 
is an outgrowth of the body-wall, with two epithelial walls and an exter- 
nal cuticle. The epithelial walls bound a vascular cavity, and are united 
by bridges or pillars in which some connective-tissue may be included. 
This intermediate tissue, mesodermic in origin, has not been previously 
described. It seems to be of some physiological importance in deter- 
mining the course of the blood. 
Parthenogenetic Cypridse/f — Dr. Richard Woltereck has investi- 
gated especially the formation and development of the egg in certain 
species of Gypris, and prefaces his paper by noting how little is really 
known of the Ostracods as compared with Phyllopods and Copepods. 
Among the special points of interest exhibited by the first named are 
the great variation in habit in nearly related forms, and the frequency 
of parthenogenesis, whether permanent, temporary (seasonal), or local. 
There is similar variation in the form and colour of the egg, and in the 
methods of egg-laying. 
The origin, growth, and maturation of the eggs were followed in 
detail, and the regular occurrence of a synaptic state in the growing eggs 
was demonstrated. As in other cases, the synapsis is indicated by the 
fusion of the chromatin threads into a ball, while the nucleolus retreats 
to the opposite end of the nucleus. When the synaptic state is over, it 
is seen that the similar germ-cells have become differentiated into ova 
and nutritive cells. The latter, demonstrable in the ovary, have broken 
down by the time the ova reach the oviduct. They are remarkable for 
their excess of chromosomes (hyperchromatosis), and for the tendency 
these have to group themselves in dyads and tetrads. These ultimately 
ajDproach nearer and nearer together, until the nucleus is filled with a 
dark amorphous mass of chromatin. In the egg-cells on the other hand 
the chromosomes diminish and disappear, the chromatin being repre- 
sented by minute microsomes, the conspicuous nucleolus appears in 
several different forms, a clear vesicle is developed in the nucleus, and 
the so-called yolk-nuclei appear in varying form in the cytoplasm. When 
the growth of the egg is completed, it is laid, and maturation begins. 
With the beginning of this process the chromosomes reappear. The 
single polar body usually divides after its formation. The process of seg- 
mentation is described in detail, and the result is to show much general 
resemblance to the conditions seen in Copepoda. 
In an interesting discussion of the theoretical value of his results, 
the author rejects the suggestion that synapsis has anything to do with 
reduction, and regards it as a suppressed mitotic division, notably be- 
cause it is preceded by a segmentation of the chromatin threads into 
chromosomes, a process which does not again occur in the egg-cells till 
* Anat. Anzeig., xv. (1898) pp. 45-51 (G figs.). 
f Zeitsclir. f. wiss, Zool., Ixiv. (1898) pp. 59G-G23 (2 pis.). 
