42 6 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Cladocera of Basle.* — Herr T. Stingelin has a preliminary notice of 
the result of two years’ work on these freshwater Crustacea. He has 
discovered no less than 68 species, among which are a number of new 
forms, and there are, as may be expected from the number, many species 
which are comparatively rare. The author has been able to convince 
himself of the local variation of various species, and he is able to show 
that in certain waters quiter different species are dominant at different 
times; forms which in the summer of 1893 were most abundant totally 
disappeared in the summer of 1894. 
Copepod Studies. | — Dr. W. Giesbrecht continues his studies on 
Copepods. He deals first with the morphology of the abdomen in the 
female. From his own researches, taken along with those of Claus, 
Maupas, and Canu, it seems almost certain that all free-living Copepods 
pass through (about) five “ Copepodid-stages ” between the last nauplius 
stage and sexual maturity. At each stage there is a moult, and with 
each moult an additional segment is gained. As Claus showed, the anterior 
portion of the last trunk-segment is periodically constricted off as a new 
one. The first Copepodid stage has five free segments between head 
and feet ; the adult has typically ten segments equally divided between 
thorax and abdomen. Bat this typical number is not found in the 
majority, and where it occurs it is usually in the males only. By sup- 
pressed division, or, more usually, by secondary coalescence, the number 
of abdominal segments is often reduced. Dr. Giesbrecht explains what 
happens in different cases. Thus, in the Gymnojplea- species, the formula 
for the abdomen in the fifth Copepodid stage is 1, 2, 3, 4 -f- 5, if it be 
four-jointed ; 1 + 2, 3, 4 -f- 5, if it be three-jointed. There are many 
similar results, but the next chapter has greater general interest. 
The author proceeds to discuss the luminosity of pelagic Copepods. 
He has observed that of Pleuromma ahdominale , PI. gracile, Leuckartia 
flavicornis , Heterochseta papilligera , Oncsea conifera a small list com- 
pared with the number of forms in which no trace of luminosity could 
be detected. After describing the varied position of the luminous glands, 
he seeks to substantiate the important conclusion that the stimulus 
provoking luminosity causes primarily the emptying of the glands, and 
that the luminosity occurs not in the living protojffasm of the glandular 
cell, but as a secondary effect of the medium on a secretion of the gland. 
There does not appear to be any reaction between the secretion of the 
luminous glands and that produced by ordinary skin glands. All that 
the author can venture to assert is that there are two necessary factors 
in producing luminosity, the secretion and water. Is the process 
chemical? If so, is there in the secretion some substance which, like 
potassium, becomes luminous in contact with water ; or does contact 
with water bring two substances in the secretion into reaction? After 
a careful review of observations and speculations, Giesbrecht concludes 
that in the phenomenon of luminosity physiological processes are 
involved only to the extent of producing the luminous substance and 
placing it in the conditions required for its being luminous. The 
luminosity itself is a secondary phenomenon, accompanying a chemical, 
* Zool. Anzeig., xviii. (1895) pp. 49-51. 
t MT. Zool. Stat. Neapel, xi. (1895) pp. 631-94 (1 fig.). . 
