CESTOIDEA ROTIFERA. 
481 
the outer gives rise to the epidermis and central nervous system; the 
inner, thinner layer develops the muscular portions. The head and ventral 
wall are represented by the germ-stripe, formed by tlie growing together of 
the four plates, whilst the covering-in of the dorsal region is a secondary 
formation. The proboscis arises as a simple inversion at the anterior end 
of the germ-stripe. A pecpliar form of P^7^c?^M??^-larva found at Odessa is 
also described by the author, in which he recognizes a rudimentary nervous 
system in thickened portions of the epidermis. An important comparison 
of the development of Echinoderms and Nemerteans follows this, and con- 
clusions as to the affinities of the Echinodermata. Twelve quarto plates 
illustrate this valuable memoir, of which two belong to the developmental 
history of the Nemerteans. 
22. Van JIeneden (jhmior) describes Macrostomum viride, n. sp., from a 
freshwater ditch at Louvain, and another found among fucoids on the coast 
of Brittany, to be called M. clajjaredii. The anatomy, and histology of the 
two forms are given with detail and precision, the first-named being figured 
in a plate, whilst figures of the second are referred to as given in the author’s 
Recherches sur la compo.sition et la signification de I’oeuf,” Mdm. cour. do 
I’Acad. Roy. de Belgique, t. xxxiv. Van Beneden is led to erect Oersted’s 
genus Macrostomum into a family, Macrostomiens, in which he recognizes 
the following genera and species : — 
Macrostomum^ CErst. 
j M. histrix, CErsted. 
\m. viride, Ed. v. Ben. 
Omaloaomum, Ed. v. Ben ) Clap. 
I O. claparedu, Ed. v. Ben. 
Mecynostomum, Ed. v. Ben M. auritum, M. Schultze. 
Some very important facts in support of the author’s views on the 
vitellogenous glands and their relation to the yelk are described. 
23. CuBiTT describes with much care the trochal disk in Stephanoceros 
and allied forms. He finds the eye to be double, and not single as stated 
by some authorities. He also finds branched nerve-cells in the so-called 
brain. He announces new views as to the contractile power of the water- 
vascular system, and declines to admit the existence of a cilium pro- 
ducing the flickering appearance ” in the vibratile tag, as described by 
Huxley in Lacimdaria. Other observations, evidently made with care, and 
therefore worthy of attention, are recorded in this paper. 
24. Hudson gives a similar essay on the structure of Synchoita. 
25. Tornaria was first described by Johannes Muller ; it has since been 
seen by Krohn, Fritz Muller, and Alex. Agassiz. MetschnikofF describes 
and figures it carefully. He points out its possible affinities, and concludes 
that, if it is not the larva of Balanoglossus, it is, at any rate, very much like 
that strange worm. 
