400 SUMMARY OF CURRENT RESEARCHES RELATING TO 



complete posteriorly; no striations were observed in the radiating mns- 

 cular fibres of the gizzard. Of the gentis Staurocephalus a new species, 

 S. australis, is described. Eulalia quadrocula is related to E. microceros 

 Clap., but the new species has four pairs of eyes, Psamathe (?) crinita may 

 turn out to be a type of a distinct genus. SipJionostoma affine is peculiar in 

 possessing a pair of very long narrow cylindrical glands opening on the 

 lateral dorsal surface of the body, just behind the head. These glands 

 extend through a considerable portion of the body, have delicate walls, and 

 contain cells inclosing small greenish particles. Halla australis is rich 

 orange in colour, and from it a purple pigment is extracted by alcohol. 

 There are seven pairs of jaws, some toothed, others not toothed. This 

 species resembles Nereis jtarlhenopeia Delia Chiaje, but the latter has not 

 the long whip-like setse. Imbedded in the substance of tlie nerve-cord, in 

 the anterior segments, are a series of eight or ten oval vesicles. Each 

 is inclosed in a fibrous capsule, pierced by nerve-fibres, and contains a 

 spherical solid body ; the author suggests that they may be a rudimentary- 

 form of otocyst. 



Conodonts.* — Herren J. V. Eohon and K. A. von Zittel have examined 

 the structure of those enigmatical bodies which Pander regarded as the 

 teeth of cartilaginous fishes of Silurian times, and find that all the forms 

 consist of parallel-layered conical laminso, arranged one over the other, 

 and sometimes traversed by fine radial canals. The structure of these 

 Conodonts has, then, nothing in common with the teeth of any fish, nor 

 with the corneous teeth of Cyclostomi, nor can they be regarded as the 

 lingual denticles of Molluscs, hooks of Cephalopods, or fractured points of 

 Crustaceans ; they do, however, agree admirably in form and structure with 

 thf» buccal apparatus of Annelida and Gephyrea. Their great multiplicity 

 of form leads us to suppose that they belonged to numerous genera and 

 species, and consequently to the inference that in the Palajozoic times the 

 shores of the sea were peopled with a great abundance of worms of very 

 different kinds. 



B. Nematheliniutlies. 



Embryology of Nematodes.! — M. P. Hallez has a note on the develop- 

 ment of the mesoderm in round-worms ; the layer starts from two cells 

 which undergo division. As they do so the two mesodermic cells become 

 smaller and smaller, while retaining their characteristic granular aspect ; 

 the two first cells grow larger and become very distinct, and will give rise 

 to the gonad ; by developing two cells posteriorly, they form the com- 

 mencement of the genital ducts. Later on the two primitive cells are 

 replaced by a small cellular mass, which is the ovary or testicle. The 

 author has as yet been unsuccessful in making out the formation of the 

 excretory apparatus. 



The 16-6tage appears to be important ; in it there are four endodermal 

 cells, of which the anterior and posterior will give rise respectively to the 

 fore and hind parts of the intestine, while the two median give rise to 

 the median part ; there are the two initial cells of the mesoderm, two 

 sexual cells, and eight ectodermal cells, of which the central is probably 

 the point of departure for the cells of the central nervous system. Thus, 

 from the beginning of segmentation, all the regions and all the organs of 

 the new being are indicated. 



* SB. Bayer. Akad. Wiss., 188G, pp. 108-36 (2 pis.), 

 t Comptes Rendus, civ. (1887) pp. 517-20. 



