1905.] NEW EXCHYTRyEID WORM. 563 



The dorsal blood-vessel is anteclitellian in origin and does notseem 

 to be connected at its point of origin with any dorsal diverticulum 

 of the gut such as exists in BucMtoltzia. It arises in the xith 

 segment. I could see no "heart body." 



Tiie exact origin of the dorsal vessel is rather difficult to locate 

 exactly in this very minute Eachytrteid. I fix the xith segment 

 as the point of emergence from the intestinal plexus, since the 

 vessel is very much broider here than iu the dorsal I'egion of the 

 blood-plexus posteriorly * and stands out more from the walls of 

 the gut. The vessel is, in fact, in this segment quite twice the 

 width that it is anterioi'ly to the point in question. Commonly, 

 for example in Henlea, nastita, the dorsal vessel is much wider at 

 its emergence from the intesfciaal plexus than it is anteriorly. 



This is confirmed by an examination of a series of transverse 

 sections, from which it was evident that the dorsal vessel stood 

 away from the walls of the intestine in the anterioi- part of the 

 clitellum ; it was indistinguishable posteriorly. 



Concerning the reproductive organs^ it may be observed, in the 

 first instance, that the position of the various ducts and pouches 

 is perfectly normal. The external orifices of the atria are very 

 conspicuous upon the ventral surface of the twelfth segment, in 

 line or nearly so with the ventral set?e of that segment. These 

 seta3 are, however, absent, and there are no penial sette of any 

 kind. The testes and the ovaries occupy their usual segments, 

 t. e. xi. and xii. Concerning tlie exact form of the sperm-duct 

 funnel I am unable to give details ; but I have identified them 

 and satisfied myself that they are of the usual Enchytrseid 

 pattern. 



The spermathecpe offer charactei'S of obvious systematic use. 

 They open on the one hand into the oesophagus in the fifth 

 segment, and on the other by a muscular duct on to the line dividing 

 segments iv. and v. I could not find any diverticula. There are 

 bat a single pair of spermatheca\ 



In the above description I have only be3n able to dwell upon 

 a certain number of facts which are of syst3matic importance in 

 the group. Of importance in determining the genus are : (1) the 

 presence of four bundles of curved setae on all the segments of 

 the body, save the first and the twelfth ; (2) intraclitellian origin 

 of dorsal vess3l ; (3) absence of any diverticula to oesophagus ; 

 (4) simplicity of spermathecae and their communication with 

 oesophagus. 



Of the thirteen genera allowed by Michaelsenf, 9, viz., Achceia, 

 Michaelsenciy M eseuchytrceus , (Jkirodrilus, Bihchholtzia, Eiichytrceus, 

 Stercutus, Marionhia, and Limihricillits, are excluded by these 

 characters. Though I did not find any dorsal pores, it is clear 



* It must be borne in mind tbat Pieraiitoui ("vStudii anatomici su Michaelsena 

 macrochceta Pierant.," Mittb. Zool. St. Neapel, xvi. 1903, p. 409) traces a distinct 

 dorsal vessel in the intestinal plexus posteriorly to the region where the former is 

 said to commence. But this does not affect tlie point of emergence. 



t Oligochffita, in ' Das Thierreich ' (Berlin, 1900). 



