564 SUMMARY OF CURRENT RESEARCHES RELATING TO 



and Caligina the author proposes the term of Eostrostomata — to which 

 there is the obvious objection that it is a vox hyhrida. The author 

 gives a table to show the systematic changes which he proposes. 



Vermes. 



Nervous System of Euniceidse.* — G. Pruvot finds in Hyalinoecia 

 tuhicola that the two central ganglia are so curved and connected 

 by a thick median commissure that there is superiorly a " ventricle " 

 which communicates by a large anterior cleft with the general cavity. 

 In the family generally we find that the cerebroid mass is made up of 

 two distinct parts, one cerebral and one stomatogastric ; the antennae 

 and the organs of sense are innervated exclusively by the posterior 

 or cerebroid portion of the mass ; the unpaired posterior appendage 

 represents a pair of appendages fused along the middle line. The 

 stomatogastric centre alone provides the nerves of the palpi and the 

 stomatogastric filaments, and the whole system presents essentially 

 just the same arrangement as the general nervous system, for there 

 is a supra-oesophageal centre, an oesophageal collar, and a ventral 

 chain of, at least, two ganglia, the lower of which appears to the 

 author to be constricted and to be formed by the fusion of what were 

 primitively two ganglionic masses. 



Cerebrum of Eunice harassii, and its relations to the Hypo- 

 dermis.f — E. Jourdan describes the cerebral ganglia oi Eunice harassii 

 as being composed of a central mass of dotted substance, which is 

 covered by a thick layer of nervous cells (the nuclear layer of 

 Ehlers). Above this, and just below the cuticle, there are epithelial 

 elements which are conical in form, and have their bases, instead of 

 terminating on a membrane, prolonged into rigid filaments, which 

 penetrate into the nuclear layer, and, by uniting, give rise to, as it 

 were, pillars which pass from the cuticle to the mass of dotted 

 substance. The protoplasm of these hypodermic cells is greatly 

 reduced, and their nuclei are characteristically fusiform. They 

 become lost in the nuclear layer, and closely fused with other fibrils, 

 which have a similar histological character, but are of a different 

 origin. 



The nuclear layer, which is rightly regarded as being nervous 

 in nature, is made up of various elements. In section the layer forms 

 a delicate plexus between the hypodermic pillars, and each of the 

 spaces is occupied by a spherical nucleus. The nerve-cells of the 

 layer are composed of a large nucleus, hardly any protoplasm, and 

 a fine enveloping membrane; they give off one or two processes, 

 which are exceedingly delicate when taken singly. 



The fibrils which are connected with them, but which, as has been 

 already said, are of different origin, arise from the nerve-cells ; though 

 their function is no doubt different to that of the hypodermic fibrils 

 their histology is absolutely the same. The spaces left in the 



* Comptes Eendus, xcviii. (1884) pp. 1492-5. 

 t Ibid., pp. 1292-4. 



