SCHIZOPODA. 
O 
o 
said to have reached that state. Still, they afford material for a re-description and 
figures of the species in the adult state, with some notes on the growth changes. 
The Mysidacea consist of eleven specimens, referable to six species. The most 
interesting of these species is Hansenomysis antarctica , an Antarctic representative of 
a genus hitherto known from but three specimens from Arctic and boreal waters. 
The chief interest of the collection lies in the evidence which it may afford as to 
the similarity or dissimilarity of the fauna at the two poles. There are no species 
common to the fauna of both polar regions iu the collection ; but, on the other hand, 
all the genera save one, Antarctomysis, are represented in northern waters by species 
which are quite distinct from their southern allies. 
Exploration of the bottom fauna of the deep waters of the globe, especially in 
tropical and sub-tropical regions, is as yet only in its infancy, and it is therefore 
extremely probable that what are now known to be bipolar genera and species will in 
future be found to be cosmopolitan in their distribution. The Schizopoda were long 
thought to have in Lophogaster typicus a stock instance of a bipolar form, but the 
gaps in its distribution have been almost completely filled up as a result of recent deep- 
sea work, and, with the exception of the tropical Atlantic, its range is known to be 
complete from Norway to the Cape. 
Two bipolar species of Mysidse are known, however— Boreomysis scyphops, G. 0. 
Sars, from Arctic waters, and Lat. 50° S., near the Crozet Islands, and Amblyops 
crozetti , from the seas of Greenland and Ian Mayen in the north and the Crozet Islands 
in the south. They are not known from the intermediate waters. 
Of the genera of Antarctic Schizopoda, Euphausia, Thysanoessa, and Eucopia are 
world-wide in range, but the northern and southern species are quite distinct, even the 
hitherto supposedly cosmopolitan Eucopia australis, Hausen having shown to contain 
at least two species, probably three. 
Pseudomma, Hansenomysis, Dactylamblyops, and Mysidetes are, as at present 
known, bipolar genera, but Pseudomma, at least, ranges far from both poles, and 
further exploration will probably extend the known range of the other genera also. 
The .most interesting case is presented by the genus Antarctomysis. It is closely 
related in structure to the northern species Michtheimysis mixta (Lilljeborg), a species 
inhabiting chiefly the colder waters of the northern hemisphere. The two genera are 
separated only in the characters of the male pleopods, which are more primitive in the 
Antarctic form, and neither genus is likely to be found to have a distribution which 
extends very far from the poles they frequent. 
In the preparation of this report I have received much valuable help from many 
sources. The authorities of the British Museum kindly allowed me to examine and 
dissect two specimens from the ‘ Challenger ’ collections in their charge. To I)r. 
Caiman, of the British Museum, I have been much indebted for information on many 
points connected with the ‘Challenger’ material, and he lias, also, at my request, 
furnished me wdtli drawings of various species. Mr. E. \Y. L. Holt kindly examined 
