"^'iSi!^,i:t" ^MMm in the Uni.

476
VERMES.
22. VAN BENEDEN, EDOUARD. Etude zoologique et anatomique
du genre Macrostomum, comprenant la description de deux
especes nouvelles. Bull. Ac. Belg. (2) t. xxx. 1870.
ROTIFERA.
23. CUBITT, CHARLES. Observations on some points in the
economy of Stephanoceros. M. Micr. J., May 1870, p. 240.
24. HUDSON, C. T. On Syncheeta mordax. M. Micr. J. July
1870, p. 26.
INCERT^E SEDIS.
25. METSCHNIKOFF, ELIAS. Ueber Tornaria. Z. wiss. Zool.
1870, p. 131.
1. CLAPAREDE describes Annelids observed in the winter of 1868-69—some
new, others mentioned already in his previous volume. The second part of
Ehler's ' Borstenwtirmer' having appeared between the publication of the
original work and this supplement, the author now avails himself of the
opportunity of replying to some criticisms and discussing some views put
forward by Ehlers. The book is very rich in anatomical, histological, and
physiological details. The remarkable history of Nereis dumerilii is given
at considerable length, with some additions to the account published in 1869
in the 'Archives Suisses,' and with the addition of four plates in illustration.
The facts already published are here reiterated :—(1) that JV. dumerilii attains
sexual maturity; (2) that some specimens of JV. dumerilii become metamorphosed
into Heteronereis, and then attain sexual maturity (probably not
the same individuals which have developed sexual organs as Nereids, but
others born from the eggs of these latter) ; (3) that there is a second Heteronereis
form also connected with JV. dumerilii, which is small and swims on
the surface, the.first form being large and tubicolous ; the two Ilcteronereisforms
develop from the Nereis-form, apparently at distinct seasons of the
year. To these facts M. Claparede now adds that a Nereid herniaphroditeform
is also included in the cycle, which, according to observations made by
Metschnikow at San Remo, is probably the same as Moquin-Tandon's hermaphrodite
Nereis from Marseilles (JV. massiliensis). When to all this is added
the fact that the form recognized as Nereis dumerilii proper (so to speak) is
itself exceedingly variable, the picture of specific indefiniteness is complete.
Nereis cuttvifcva and its Heteronereid form are also described in this work; but,
says M. Claparede;, there is no reason to suppose here the existence of sexual
maturity in both Nereis- and Heteronereis-form. All specimens exhibiting
ova or spermatozoa were already partially metamorphosed into the Heteroneveis-form.
The discovery that Heteronereis is but the sexual condition of
species of Nereis belongs to M. Malmgren. M. Claparede has shown how
complicated the condition of things becomes in some cases by the development
of sexual organs in the larvae (for so the Nereids may be called),