890 SUMMAKY OF CUBRENT RESEARCHES RELATING TO 



paper into their burrows ; and it was found that in the case of leaves, 

 that part of the leaf was, in the great majority of cases, seized by 

 which the leaf would present the least resistance. Nearly three times 

 as many of the triangles were drawn in by the apex as by the base. 



Prefecundation in Spic* — A. Giard has observed that in the 

 Spio crenaticornis of Montagu the mature ovum has the form of a 

 spheroid, considerably flattened at its two j)oles ; around the equator 

 there are about twenty transparent vesicles connected with the vitel- 

 line membrane; their function would appear to be that of micro- 

 pyles, and the author can only compare them with the follicular 

 elements of the Ascidians. The germinal vesicle is very large and the 

 always central nucleolus is likewise voluminous. Some time before 

 the maturation of the ovum we may see in the germinal vesicle, at 

 some distance from the nucleolus, a smaller cellular body ; this 

 eccentric element is nucleated ; it approaches and gradually becomes 

 applied to the nucleolus, when it loses its own nucleus and becomes 

 at last reduced to a double membrane surrounding the nucleolus of 

 the egg, with which it finally so fuses that no sign of this phenomenon 

 is left in the egg. Nothing is known as to how this element pene- 

 trates, and the significance of the phenomenon still remains to be 

 explained by further and wider observations. 



Northern Gephyrea."]" — In this magnificent addition to the litera- 

 ture of the Northern Seas, D. C. Danielssen and J. Keren give 

 in Norwegian and English (in parallel columns) a full account of 

 the results of their studies on a group to which in this year so much 

 attention has been directed. The ten genera and sixteen species (of 

 some of which, unfortunately, only a single specimen was obtained) 

 comprise two new families, four new genera and seven new species, 

 some of which are of the greatest significance. 



Phascolosoma liUJehorgi n. sp., has a proboscis which is equal in 

 length to the trunk, and is studded with minute pointed papillae. 

 Aspidosiphon armatum n. sp., has the surface of its body provided 

 with chitinous plates, varying in size and arranged round the apertures 

 of the glands of the skin. There are a number of chitinous hooks on 

 the proboscis. Onchnesoma glaciale has a proboscis which is twice as 

 long as the trunk, and the chitinous hooks are confined to its anterior 

 fourth. The skin is hyaline. Stephanostoma hanseni n. g, et sp., has 

 an oral disk which is exceedingly broad and carries, in addition to a 

 few scattered tentacles, one large group of tentacular organs; the 

 body is cylindrical, and the proboscis and trunk are about equal in 

 length. The anal orifice lies close to the base of the proboscis. A new 

 genus (Hamingia) is added to the family Bonellidse (H. arctica n. sp.), 

 from the other two genera of which it difi"ers, however, in the absence 

 of bristles and of a proboscis. In consequence of the absence of this 

 latter organ the circulatory and nervous systems are somewhat 

 modified ; at the anterior extremity of the perivisceral cavity there is 

 a floating muscular organ which appears to have the function of a 



* Coniptes Reudus, xciii. (ISSl) pp. GOO-2. 



t ' Den Norskc Nordliavs Expeilitiou,' iii. (1881) GO pp. (G pis. and 1 map). 



