612 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
There are four pairs of gonads which, up to a certain point, develope 
equally ; later on, the gonad of segment xii. degenerates. Four pairs of 
genital ducts are developed from nephridial funnels and a short section 
of the succeeding tube. The young embryo is provided with an un- 
paired sense-organ which consists of a few large embryonic cells, and is 
placed on one side of the stomodmal aperture. In the epidermis of the 
very advanced embryo there are peculiar cells which may possibly be 
sense-organs. 
Central Nervous System of Earthworm.* * * § — M. P. Cerfontaine has 
investigated the structure of the so-called giant-fibres of Leydig, which 
have been the cause of so much discussion. He comes to the conclusion 
that they are nervous in nature, and that they are quite special nerve- 
fibres which are due to the union of the prolonged cylinder-axes of 
several cells. As the median giant-fibre arises anteriorly and is directed 
backwards, its nerve-current is antero-posterior. The direction of 
development, and therefore of the nerve-current, is postero-anterior in 
the lateral fibres. On their course the giant-fibres give rise, in each 
ganglion, to ramifications which put them into relation either with 
other elements of the chain or with the periphery. These fibres ought 
to be considered as very complex nervous formations, which have to 
establish connections between the different parts of the nervous system. 
In fact the author thinks that it is the possession of these fibres which 
allows of the simultaneous production of muscular contractions in all 
parts of the body of the earthworm. 
By applying the method of Ehrlich it was found that the number of 
cells which enter into the constitution of one ganglion is larger than can 
be shown in a drawing, and the same is true of the columns of nerve- 
fibres. 
A Double-headed Earthworm.! — The Bev. H. Friend has a brief 
note on a species of Allolobophora longa Ude, in which the head is 
double ; the second head appears to consist of two segments only. 
New Genus of Oligochaeta.J — Mr. F. E. Beddard describes under 
the name of Gordiodrilus a new genus of Oligocheeta, which he places 
near to Ocnerodrilus. Four of the new species of the genus are from 
West Africa, and the fifth from the island of Dominica. So far as the 
atrial pores are double and the opening of the vasa deferentia inde- 
pendent this new form resembles Acanthodrilus, but it, with Ocnerodrilus 
and Moniligaster , alone amongst the terricolous forms, agrees with the 
aquatic genera in having the lining of the atrium formed by a single 
row of cells. For the present the new genus is placed in the family 
Ocnerodrilidm. 
Dissemination of Hirudinea by Palmipedes. § — M. J. de Guerne 
brings together several instances which show that leeches may be carried 
from place to place by wild ducks and other Palmipedes. One leech, 
* Bull. Acad. Boy. de Belgique, 1892, pp. 742-52 (2 pis.). 
t Science-Gossip, 1892, p. 161 (2 figs.). 
X Ann. and Mag. Nat. Hist., x. (1892) pp. 74-97 (2 pis.). 
§ Comptes Bendus Soc. Biol., 30 Jan., 1892. See Ann. and Mag. Nat. Hist., x. 
(1892) pp. 117-20. 
