Full resolution (JPEG) - On this page / på denna sida - Sidor ...
<< prev. page << föreg. sida << >> nästa sida >> next page >>
Below is the raw OCR text
from the above scanned image.
Do you see an error? Proofread the page now!
Här nedan syns maskintolkade texten från faksimilbilden ovan.
Ser du något fel? Korrekturläs sidan nu!
This page has never been proofread. / Denna sida har aldrig korrekturlästs.
from physiology and oecology as from morphology. We liave not the right to prefer one
character to another. We must try to give a picture that is as correct
and complete as possible of the species as we find i t in nature.
This programme puts a gigantic task before us, but nature is work.
It is of course not only from the point of view of the identification of species that it is
desirable to pay attention to as many characters as possible. The descriptions of species are
not only useful for a barely certain identification. They are also to enable us to decide
the mutual relationships of the forms described. The descriptions of the species form the basis
on which in most cases the investigation of the natural system of a group almost exclusi vely
must rest.
If attention is paid to only a few organs this obviously présupposés that the characters
that are not taken into considération are quite constant or, if they are variable, that their
variation is accompanied by corrélative changes in the organs that are included in the diagnosis
or of which reproductions are given. A constancy or corrélation of this kind seems of course,
even a priori, very improbable. I myself have observed a great many instances in which it
does not exist.
A good illustration of this is shown by the two species described below belonging to the
sub-family Cypridininae, namely Cypridina (Doloria) levis and C. (]).) pectinata. —I may mention
in passing that these two forms played a considérable part in the development of my studies
of this group of animais, as it was during the examination of them that I realized the necessity
of departing from the old-established superficial methods of investigation and description. —
These two species show a striking resemblance with regard to the length and the type of the
shell, the endopodite of the second antenna, the seventh limb and the furca, in other words,
those organs to which in the group Cypridiniformes (cf. below) attention had hitherto been
almost exclusively paid. I too assumed at first that they were quite identical. Only after
the number of species investigated by me was increased and I had observed that there was a
great difference between the Ostracods of South Georgia and those of the Falkland Islands —
Tierra del Fuego did I undertake a detailed re-examination of specimens from both these regions,
paying attention not only to the organs mentioned above but to the other organs as well. It
was only then that I discovered that this was a case of two very well differentiated species
and that profound differences were present, especially in the maxilla and the fifth limb,
in other words two organs to which practically no attention had formerly been given
in this group.
As a proof of how necessary it is to observe carefully in each form the conditions of the
various characters and not to attempt a prématuré generalization, some examples may also be
given, taken from forms treated in the present portion of my work. In the sub-genus Cypridina
the number of furcal claws is quite constant. In some other sub-genera and genera of the
sub-family Cypridininae this character is constant in each species, but on the other hånd
it is variable for the sub-genus or genus considered as a whole. Finally in a number of species
in this sub-family the number of the furcal claws differs not onlv from individual to individual
but sometimes even on the two furcal lamellae of the same individual. Similar conditions may
Zoolog, bidrag, Uppsala. Suppl .-Bd. I.
Some reasons for the
neiv method.
<< prev. page << föreg. sida << >> nästa sida >> next page >>
