150 Transactions of the Society. 



9 Segm., meist einfach, selten mit nepliridialen (?) Elementen 

 verbunden. 2 Paar Prostaten (selteu verdoppelt) miiuden getrennt 

 von den Samenleitern aus ; 1 Paar Hoden frei im 10 Segm. (Hoden 

 bei wenigen Arten nicht beobachtet). Samentaschen meist ohne 

 Divertikel, selten mit Aussackungen am distalen Ende der AmpuUe 

 (Divertikel ?)." 



Possibly further research will show the need of a modification 

 of this definition. As at present understood, we find the genus 

 including species which show widely divergent characters, such as 

 the presence or absence of a gizzard, diverticula to spermathecse, 

 pigmentation, etc. The spermathecpe may be either one or two 

 pairs, and the two pairs of prostates may be doubled. On the 

 other hand, in some cases the gizzard is rudimentary, and so acts 

 as a bridge between the species which possess one and those which 

 are destitute of that organ ; and the definition as set out by 

 Michaelsen makes it impossible to remain in doubt whether or not 

 a given species should be called Acanthodrilus, Ocnerodrilus or 

 Kerria, as was the case in earlier days. Indeed, Ocnerodrilus has 

 now been raised to a sub-family of which Kerria is one of the 



genera. 



IV. — Description of Kerria ruhra sp. n. 



Two years ago, while on a visit to Oxford, I found in the Lily 

 House at the Botanic Garden a species of worm which I had not 

 previously seen. It lived in the oozy mud which surrounded the 

 plants on one side of the tank, and was accompanied by Fheretima 

 (indica 1). Unfortunately, it proved so tender and susceptible to 

 adverse influences that when I reached home it had perished, and 

 the relics were beyond recognition. I had, however, assured 

 myself that, whatever the worm might be, it had never been 

 recorded for this country, even as an alien. I therefore availed 

 myself of the earliest opportunity which presented itself of again 

 visiting the Garden, in the liope of obtaining further material. 

 Though the creature was not abundant, I had the good fortune on 

 June 21st, 1915, to secure two adults, and it is upon these that the 

 following observations are based. 



External Characters. — Kerria rubra is a very slender, delicate 

 worm, extending while alive to two or three inches in length, but 

 contracting to about Ih in. in alcohol. It does not exceed 2 mm. 

 in its greatest diameter, which is in the region of the girdle. The 

 colour is red in the living worm, but the pigment disappears when 

 it is preserved, and the region behind the girdle is so transparent 

 as to admit of the nephridia being readily seen as large white con- 

 voluted bodies. It closely resembles a slender specimen of Helo- 

 drilus ocidatus Hoffm. 



The number of segments is about ninety ; the setae number eight, 



