20 TAGE SKOGSBERG, A NEW FRESH-WATER OSTRACOD. 
that will be treated in a later paper — have, if I am not mistaken, hitherto been 
overlooked. 
It may be asked if in spite of the important differences, stated above, in the 
distal ' bristles of the second endopodit joint of the second antenna of males and 
females the homology of these bristles may nevertheless be established. The great 
agreement between the sexes in the bristles of the other extremities and the other 
bristles of the second antenna and especially the fact that, in spite of great dissimi- 
larity at first sight, the same number of bristles occurs in both sexes make an 
assumption of homology extremely plausible. 
If homology does exist, which bristles correspond to each other? 
Three bristles of the male, the two long and narrow lateral bristles situated 
at about the middle height of the joint, the one a little proximally to the other, 
and the small posterior one, the sensorial function of which is somewhat uncertain, 
show such a striking resemblance with three bristles of the female both in size and 
shape as well as in their position that their homology with these bristles can hardly 
be doubted. As to the other four a close comparison between the sexes will simi- 
larly show a striking agreement in the arrangement. As will be seen from the above, 
two of them are medial, one situated just within the end-joint, the other a little in 
front of the other; in the male the posterior of them scarcely attains the double 
length of the end-joint, the anterior is developed as a rather weak claw only a little 
longer than the posterior; in females these bristles are represented by the two long 
and powerful claws. The other two of these four bristles are in both sexes situated 
in front of the two last-mentioned, the one somewhat in front of the other; the 
posterior of them is median, the anterior lateral; in the female sex these bristles are 
represented by the short and strong dorsal claw and the short and narrow dorsal 
bristle; in the male they are represented by the two main-claws. Homology of the 
bristles according to the arrangement consequently necessitates fundamental diffe- 
rences in their development in the two sexes. 
If on the other hand we try to homologize these four bristles according to 
their development, a procedure which seems to be supported by the fact that in 
both sexes they exhibit almost similar types, viz. two main-claws, one short claw, 
and one short ordinary bristle, we must assume so complete a modification of the 
arrangement as to make such a supposition anything but probable. — I shall return 
to this question in a further paper in which I shall be able to illustrate it by 
examples taken from several species of other genera. 
As to the cause of this dimorphism, in other words with reference to the dif- 
ferences in the application of these bristles in the two sexes, nothing can be said, 
our knowledge of the biology of these small creatures being still too imperfect. It 
may, however be mentioned that this antenna, as stated by S. JENSEN, is used by 
the males in seizing the females. 
The variability of the furca of this species is to be noticed, tbis organ in seve- 
ral other species of this subgenus — judging from the descriptions — being of a high 
diagnostic value. 
