631 



XIV. A Contribution to the Knowledge of the Lower Annelid*. 

 By E. Ray Lankester, Esq. Communicated by George Busk, Em., Sec. L.S 



(Plates XLVIII. & XLIX.) 



Read December 5th, 1S67. 



Contexts. 



I. The anatomy and fissiparous reproduction of the a^ vual Ch(?toga*l<r lima- . r. Bar. 

 II. Eemarks on Chcetogaster niveus, Ehr. 



JEoloso 



JEoIosoma to other low Annelida 



I. The Anatomy and Fissiparous 'Reproduction of Chaetogaster limnoei, ton Bar. 



HlSTOBY. — The minute worm which is found parasitic on specimens of L imtHM i and 

 Flanorbis, and which is remarkable as being at present the only recorded instance of n 

 parasitic Chtetopodous Annelid, has been referred to under various specific names In 

 different writers. Owing to imperfect description it has become quite impossible to 

 recognize clearly what species some of the earlier authors meant to indicate by their 

 names, and we have now the following list from which to choose— Nais vermicularis of 

 Miiller, Chcetogaster limncei of von Bar, Nais diaphana and N. diastropha of Gruithuisen, 

 Ch. furcatus and Ch. niveus of Ehrenberg, Mutzia heterodactyla of Vogt, Chcetogaster 

 Milleri of D'Udekem. Of these, it appears that Miiller probably included two species 

 under his name N. vermicularis, whilst von Bar's species, Ch. limncei, is distinct from 

 Gruithuisen's free-living N. diaphana. Ehrenberg distinguishes two species, Ins Ch. fur- 

 catus being probably synonymous with von Bar's Ch. limncei or Gmithuisen's N diaphana, 

 whilst his Ch. niveus is a distinct free-living species. D'Udekem speaks of two species 

 (probably the same two as Ehrenberg) as Ch. diaphanus and Ch. MUlen ; it is not pos 

 however, from his very brief notice, to tell what are the characters of his species, 

 and Baird use Midler's specific name vermicularis, and do not give definite character 

 whilst Oscar Schmidt, in a general anatomical paper, speaks of Ch. diaph^usme^ 



Grube 



probably Gruithuisen's species, which is the same as that f.uured by Le> 



' Lehrbuch' and in his beautiful plates of the nervous system of Annulosa. Item to,* 



appears pretty evident that von Bar's name of Caster Um*~ has prm * for th 



species /am about to describe, and tbat there £ ^^^Z^^^X 



speak further) to which Muller's name might be applied, but « , 



it will be better to call with Ehrenberg Ch. niceus; also that ttoe» **^%2 



Ch. diaphanus, differing in some details from Ch. limn*. ^f^^terZ a , f 



sete and in it size The only recent accounts of the anatomy of Ch <Btog.de a. e a bru f 



setse ana m its size, ine omy nxt. TowhVs two figures, which are not by 



note by O. Schmidt on the nervous system, and Leydig s t« o n , 



any means complete. Q „: m „ n , of Limnceus slagnalis, and also 



General Appearance and m,bit*.-On most specimens oi Urn Mm g ^ . 



VOL. XXVI. 



