KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND. 15. N:0 7. 35 



14 th segment, in the latter species, however, not always in all of the segments at the 

 same time, as one individual had them in the ll th and 12 th , another in the ll th , 12 th , 

 13 th , 14 th and only one individual in all the segments enumerated. 



The entire testes of this species are very rnuch like those of the common 

 form, but the lobated ones in the cingulurn exhibit cprite a peculiar appearance. It 

 consists rather of a nuinber of more or less round balls, united or surrounded by a 

 fine, translncent membrane, which from the least touch would break and cause the 

 small globules to float freely in the surrounding fluid. 



In the genus Mesenchytrceus said cysts containing spermatozoa enter unbroken in 

 the efferent duct, but in the two other genera their contents are emptied before, and 

 the efferent vesicle is being filled by unencysted spermatozoa. I consider this circum- 

 stance a good character of the respective genera. Accordingly when the tails of the 

 spermatozoa are seen protruding from the interiör opening of the efferent vesicle, we 

 may be pretty sure that we have before us a species either of Neoenchytrceus or of 

 ArchiencJiytrceus. 



If no tails are seen or if the vesicle is full of small round cysts we may suspect 

 a species of Mesenchytrceus. 



The outside membrane of the above cysts is in M. mirabilis covered by small 

 warts, which, however, are only visible when highly magnified. 



In most of the species we find but one pair of testes extending through the se- 

 veral segments, but in some of the species of Mesenchytrceus the testes are disconnected 

 by a short and narrow string running parallel and near the ventral ganglion, 



Two pairs of testes are also found in N. hyalinus. In A. Levinseni the testes 

 are very minute, and only occupying a very small part of the 10 th segment. 



Efferent duct. 



The external appearance of the efferent duct varies very little in the different 

 species, and may here be disregarded as being sufficiently described under the different 

 species. The beautiful and regular forms described and figured by Clapakede are not 

 met with in the species I have had under investigation. 



The three different parts: the vesicle (Samentrichter), the tube or duct proper and 

 the organ of copulation or penis, exist in all the species of the genera ÅreMenchytrceus 

 and Neoenchytrceus, and their relative size and form is about the same every where, 

 with very few and slight exceptions. In Mesenchytrceus on the contrary we meet with 

 somewhat different forms. The tube is here comparatively short and wide, never rnore 

 than 10 times longer than the vesicle, but generally much shorter. In M. priincevus it 

 can hardly be said to exist at all, as the lower end of the vesicle tapers downward 

 and unites itself with the penis without any intermediate tube. In Mesenchytrceus mi- 

 rabilis, a species so remarkable on account of the variation of its organs, the tube was 

 found in some specimens twice as long as in others, but I suppose that the one of the greater 

 size is the most common, it being found with the majority of the specimens dissected. 



