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Transactions of the Wisconsin Academy of Sciences, Arts and Letters
volume VIII (1888-1891)

Birge, Edward A.
List of crustacea Cladocera from Madison, Wisconsin ,   pp. 379-Plate XIII ff. PDF (7.9 MB)


Page 387


            List of Crustacea Cladocera from Madison, Wis.      387
   Sida, Limnosida and Daphnella have short, fleshy knobs rather than
   -hooks, and Latona is devoid of any special structure. Bolopedium has
   a hook similar to that of Latonopsis but much longer, as is natural in
   that genus.
     The new hatched male has the copulatory organ in the form of a pair
   ,of small buds, which do not reach the adult form until after four or
five
   moultings. The antennule of the young male differs widely from the
   adult form  It is short, lacks the appendix ciliata, and shows a distinct
   suture between base and flagellum. The latter is covered with long stragg-
   ling hairs. The whole structure closely resembles the female anten-
   nule. It is clear that the extension of the male antennule beyond the
   sense-hairs in the homologue of the flagellum of the female.
                          RELATIONS OF THE GENUS.
     Sars was entirely justified in separating Latonopsis from Latona. While
   the structure of the two genera is quite similar in the female, the male
   differs widely from tht of Latona. The antenna is more like that of
   Daphnella Luan that of a y other genus, especially in the rami, while
the
   great development of the base is like that of Latona. The antennule is
   peculiar and shows an intermediate stage between that of Latona and
   Daphnella, though nearer the former. In the male, however, the anten-
   nule is more like that of Sida than that of Latona. In the form of the
   body, the outline of the head, in the fornices, the position of the eye,
   eye-muscles and optic ganglion; in the heart; in the shape of the cara-
   pace, and the development of the setae of the carapace,- it approaches
   Latona. It lacks entirely the peculiar development of the antenna seen
--in-Latona and 'the plate on the lower side of the head; while Latona
   lacks the development of the shell-gland, which Latonopsis shows. In
   most of the points of resemblance and difference between the two
   genera, Latonopsis is nearer the ordinary form of the Sididce, and it
   may be considered as connecting Latona with the other Sididae, but
   with many cross-relations to other genera.
                       RELATIONS OF THE TWO SPECIES.
    L. occidentalis is very close to L. australis. Indeed, I am not sure
but
  that they are really the same species. There are many points of minor
  difference, but the most tangible is the antennule, which is about twice
  as long in the American form. It must not be forgotten, however, that
  Sars' specimens were hatched from mud, and it may be possible that
  specimens collected in their native waters will agree more closely with
  the American species. If the difference is constant, L. australis is nearer
  the ordinary type of the Sididce in the structure of the antennule.
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