476 VERMES. 
22. Van Beneden, Edouard. Etude zoologique et anatomique 
du genre Macrostomumj comprenant la description de deux 
especes nouvelles. Bull. Ac. Belg. (2) t. xxx. 1870. 
EOTIFEBA. 
23. CuBiTT, Charles. Observations on some points in the 
economy of Stephanoceros. M. Micr. J., May 1870, p. 2 10. 
24. Hudson, C. T. On Synchceta morclax. M. Micr. J. July 
1870, p. 26. 
Incert^ sedis. 
25. MetschnikofPj Elias. Ueber Tornaria. Z. wiss. Zool. 
1870, p. 131. 
1. Claparede describes Annelids observed in the winter of 1868-69 — some 
new, others jnentioned already in his previous volume. The second part of 
Ehler’s ‘ Borstenwurmer’ 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 A. dumerilii attains 
sexual maturity ; (2) that some specimens of N. dumerilii become meta- 
morphosed into Ileterotiereis, 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 Ilete- 
ronereis form also connected with N. dumerilii, which is small and swims on 
the surface, the^first form being large and tubicolous ; the two Ileteronereis- 
forms develop from the Nereis-iorm. apparently at distinct seasons of the 
year. To these facts M. Claparede now adds that a Nereid hermaphrodite- 
form is also included in the cycle, which, according to observations made by 
Metschnikow at San Remo, is probably the same as Moquin-Tandon’s herma- 
phrodite Nereis from Marseilles {N. massiliensis). When to all this is added 
the fact that the form recognized as Nereis dumetilii proper (so to speak) is 
itself exceedingly variable, the picture of specific indefiniteness is complete. 
Nereis cultrifera and its Ileteronereid 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 Ileteronei'eis-iorm.. All specimens exhibiting 
ova or spermatozoa were already partially metamorphosed into the Iletero- 
net'eis-iovxa. The discovery that Ileteronereis 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 develop- 
ment of sexual organs in the larvae (for so the Nereids may be called),* 
