SOME ANNELIDS OF THE THAMES VALLEY. 97 



all o£ small size, and are found in fresh-water in almost every part of the 

 globe. There are usually no internal septa to mark the segments, which can, 

 however, easily be numbered by aid of the setse. These are in four bundles 

 of one to six, chiefly capilliform. The girdle appears in the adult on the 

 under surface of segments 5-7, and the spermathecse, which number 1-3 

 pairs in segments 3-5, are simple, being destitute of diverticula. The 

 prostomium is large in proportion to the size of the worm, and is ciliated on 

 the ventral surface. The worm can be propagated asexually. by a process of 

 division without the formation of a budding zone such as one sees continually 

 in the Naidida3. 



1. J^OLOSOMA HEADLEYi, Beddard. (Monograph, p. 186.) 



Set?e entirely capilliform. Integumental globules bright green, occasionally 

 verging towards blue. Found in a tank at the Zoological Gardens, London. 



2. Jl^OLOSOMA HEMPKiCHii, Elirenher<j. (Symb. Phys. 1831.) For 

 synonymy see Beddard, ' Monograph,' p. 183, and ' Das Tierreich,' x. p. 14 ; 

 Lankester in Trans. Linn. fSoc. vol. xxvi. 1867, p. 641. 



Family ISTaidid^. 



This is a very large family, to which many additions have been made 

 since the publication of Beddard's ' Monograph^ and of ' Das Tierreich.' 

 Unfortunately the British species have received little attention since the days 

 of Bousfield and Bourne, but I have been able during the past year to add 

 somewhat to our knowledge of the indigenous species. The setse are some- 

 times wanting in the anterior segments either entirely or from the dorsum, 

 and are of various kinds. Some of the species have rudimentar}^ eyes, and 

 asexual as well as sexual reproduction occurs. The sexual organs are 

 situated as far forward as the fifth segment. Occasionally the nephridia fail, 

 but usually they are large for the size of the worm. These annelids form 

 beautiful objects for the microscope. Following Michaelsen our first genus 

 is Paranais. 



1. Paranais naidina, Bretsclier. (Revue Suisse de Zool. 1896, vol. ii. 

 p. 508 ; 1899, vol. vi. p. 393 ; Das Tierreich, x. p. 18.) 



Unknown in England till August last^ when I found it in the Thames at 

 Kew. Eyes may be present or absent. The first segment is very narrow, 

 and the dorsal setse commence on the second. There are five or six setse in 

 •each set from segments 2 to 5. The brain is deeply notched behind. 

 The worm is about 8 mm. in length, and in August was undergoing asexual 

 reproduction, some 20 segments going to the perfect worm. Found by 

 Bretscher (10) in Switzerland (Ziirich). 



