G30 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
and Mydiris. He then proceeds to compare these amphibious Decapods 
with other non-amphibious forms from the temperate seas. In com- 
paring them with the common crab, he points out how differently the 
appendages are articulated to the body, and how the peculiar setae 
which are found on the lower parts of the body of amphibious forms are 
altogether wanting in Cancer. There are differences also in the form 
of the carapace, in the meropodites of the walking feet, and in the 
characters of the forceps. Comparison is then instituted between the 
amphibious forms and Hyas araneus , and also Nephrops norvegicus. 
These examples of exclusively water-breathing Crustacea of various 
families show that the morphological peculiarities of the amphibious 
forms are independent of one another, but that they are due to their 
special modes of life. In conclusion, Prof. Aurivillus discusses in a 
general way the morphological peculiarities of the amphibious forms, 
and -shows how great has been the influence of their mode of life on 
various parts of their bodies. 
Crangonidse.* — Mr. A. E. Ortmann has made a study of the systematic 
and geographical distribution of this family of Decapods, which is a true 
marine group characterised by the adaptation of most of its members to 
the cold water of the Arctic and deep-sea regions. The absence of the 
group from Tertiary deposits agrees with their morphological characters 
and their supposed recent development. The genus Pontocaris is, no 
doubt, the most primitive of the family in regard to the sculpture of the 
carapace, the number of gills, and the shape of the second pair of 
walking limbs; from it arise two divergent branches. The author 
gives a technical definition of the family and of the genera, together 
with full details as to the geographical distribution of the species. The 
regions of life in which Crangonidae are found are the littoral and the 
abyssal. These habits admit of a universal distribution of the family, 
but the genera and species are more restricted. The littoral species 
especially are confined by barriers, and only a few species are adapted 
to the warmer seas. By adaptation to a cooler temperature a large 
number of these Crustacea are able to descend to greater depths, and, 
thanks to this habit, they may enter and cross the tropics in the deep 
sea. The species adapted to greater depths show, as is usual, a very 
large horizontal range. Only the true Arctic species are able to live 
along the most northern shores of America and Asia, and so show a 
circumpolar distribution. On the shores of the Atlantic and Pacific, 
however, nearly allied species are sometimes found. These must be 
derived from common ancestors living when the Arctic Ocean was not 
so cold as at present. Later these species retreated more southwards, 
and by the topical separation of their range the morphological cha- 
racters would change, and distinct forms be developed. Within the 
limits of the Arctic region we can distinguish three sub-regions : — 
(1) The Arctic circumpolar. (2) The Atlantic boreal. (3) The Pacific 
boreal. The Arctic littoral region is the centre of origin of the family, 
and the centre of its development. 
Otocysts of Mysis.f — Herr A. Bethe discusses these structures, which 
occur, as is well known, in the root of the median caudal appendages. 
* Proc. Act'd. Philad., pp. 173-97. 
t Zool. Jahrb. Abth. Anat., viii. (1895) pp. 544-64 (1 pi.). 
