Dr. W, Michaelsen on the Enchytreeidffi. 423 



Mesenchytrceus Jlavidus, nov. spec, 



is a rather dry-skinned worm of a yellowish colour, about 

 12 millim. in length. Its sette are like those of M. Beumeri 

 (fig. 1 a) , and there are as many as five in a tuft. The 

 lymph- corpuscles I have been able to observe only in pre- 

 served specimens. They are small and appear to be irre- 

 gularly elongate-oval. The head-pore is situated at the apex 

 of the head-lobe. The cerebrum (fig. 2 h) is slightly concave 

 behind, deeply emarginate in front, with parallel lateral 

 margins, and somewhat longer than broad. The segmental 

 organs (fig. 2 c) are of irregular form, with the peculiarities 

 above described as characteristic of the Mesenchytrcei. The 

 blood is colourless ; the dorsal vessel originates in segment 

 XIII. The seminal ducts (fig. 2 d) consist of a barrel-shaped 

 seminal funnel with an everted margin and a short seminal 

 canal, which is at the utmost five times as long as the funnel. 

 The seminal canal leads into the wider pole of a pyriform 

 penis and opens outwards through its narrower pole. The 

 aperture is beset with small, lobiform, prostate glands. The 

 oviducts are narrow and rather short. The seminal sacs 

 (fig. 2 a) possess a simple efferent duct, furnished at its aper- 

 ture with a slight bulbous dilatation, and a simple pyriform 

 main portion, which communicates with the intestine at its 

 apex. The cingulum, as in M. Beumeri^ occupies the posterior 

 half of segment xi. and the whole of segments xii. and xiii. 

 M. Jlavidus lives in yellow rotten tree-stumps in the 

 Borstler Jager, near Hamburg, and under moss in woods 

 near Witten a. d. Ruhr in Westphalia. 



Genus BuCHHOLZiA, aut. (9). 



The peculiar circumstance that in the long-known species, 

 first described by Buchholz * as Encliytrceus appendicidatuSj 

 a displacement of the sexual parts has taken place, induced 

 me, as it coincided with other essential peculiarities, to sepa- 

 rate this Enchytrgeid from the genus Encliytrceus^ and to 

 establish for it a distinct genus, to which I gave the name of 

 Buchholzia. Investigations upon a species recently disco- 

 vered by me, which comes so near to B. appendiculata that 

 it cannot be separated from it by generic limits, compel me, 

 however, to remove the definitions relating to the peculiarities 

 of the sexual organs from the diagnosis of the genus. The new 



* (10) Buchholz, " Beitrage zur Anatomie der Gattung Ejichytrmis,^' 

 in Schriften d. physikal.-oknn. Gesellsch. z. Kbnigsberg, 1862. 



