58 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
whole region of the eyes and the nauplius appendages ; from the second 
arises the region of the body behind the mandibles. 
The author gives interesting details in regard to the remarkably 
strict regularity in the cell-divisions of the ectodermic germinal area. 
The “ Urzellen ” always divide so that the equatorial plane is at right 
angles to the longitudinal axis of the embryo, and their descendants 
keep up this regularity for a long time, alwaj^s dividing equally, and 
spreading in regular rows from the median ventral line sidewards. 
As to the ventral nerve-cord, Bergh shows that the ectodermic cells 
in that region arise as “ Urzellen,” which by repeated division (budding) 
form cell-rows, spreading inwards. 
When the development of My sis is compared with that of Annelids 
(Oligochseta and Hirudinea), the first point of resemblance consists in 
the manner of growth — the budding of “ Urzellen ” and the serial 
arrangement of the resulting cells. But in the Oligochaeta and Hiru- 
dinea the ectoderm cell-rows of the germinal area are generally covered 
by the epidermis, whereas in Mysis they lie quite freely, and even give 
origin to the epidermis of the related region. Moreover, in the Oligo- 
chaeta and in Clepsine the cell-rows are rudiments of quite definite organs, 
while in Mysis they form the material for all the ectodermic structures 
of the given region. Perhaps the Polychaeta may be more thoroughly 
congruent. It may also be noted that the number of ectoderm “ Urzellen” 
and of myoblasts in Mysis and other Crustacea is much greater than in 
Annelids. But more material must be collected before any thorough- 
going comparison can be made. 
Antennae of Cyclopidae.* — Herr Al. Mrazek finds the origin of the 
antennae of Cyclopidae in the type possessed by Calanidae. A change 
of life and associated changes in the function of the antennae brought 
about the transition from a morphologically many-jointed, but physio- 
logically unjointed, type to one in which the joints become func- 
tional. The difference between the physiological and the morphological 
segments can still be made out. The segments forming a physiological 
segment are more intimately connected than those which belong to two 
different (physiological) segments, and eventually they may fuse. 
The Genus Cyclops, j — Herr 0. Sclimeil has begun a monograph of 
the fresh-water Copepods of Germany. At the outset he discusses the 
recent contributions, progressive and otherwise, which have been made 
to our knowledge of the systematic relations of these Crustaceans. In 
18G3 Claus recognized 14 German species, now 49 are known, and 
additions to the list must be looked for. After giving diagnoses of the 
three families Cyclopidae, Harpacticidae, and Calanidae, the author gives 
a general description of the genus Cyclops , and the rest of his mono- 
graph, so far as the parts have reached us, consists of descriptions of 
23 species of Cyclops . 
The Pontellidse.J — Prof. C. Claus begins his discussion of this 
family with an account of the antennae and their development ; he then 
describes the nauplius larvae and the cyclopid stages, and finally passes 
* Zool. Anzeig., xvi. (1893) pp. 376-85. 
t Bibliotheca Zool. (Leuckart and Chun), Heft 11, pp. 1-184 (8 pis ). 
j Albeit. Zool. Inst. Univ. Wien (Claus), x. (1893) pp. 233-82 (5 pis ). 
