273 
the genitalia of jEolosoma. These are the only notices of 
the sexual state in the genus Chaetogaster that I know of. 
It is important to state that d’Udekem, in a previous paper 
in vol. xxxi of the ‘ Memoirs of the Belg. Academy,’ 1858- 
59, recognised three species of Chaetogaster, viz. Ch. dia- 
phanus of Gruithiusen ; Ch. Midleri, supposed by d’Udekem 
to have been confused by Muller with Ch. diaphanus ; and 
Ch. Limncei of Von Bar. In my paper in the Linnean 
Society’s * Transactions’ above referred to, I have given an 
account of the synonymy of the species of Chaetogaster as far 
as my knowledge would permit. Having overlooked the 
reference to Chaetogaster in this well-known essay by 
d’Udekem on the classification of Oligochaeta, I had inde- 
pendently come to the conclusion that three species 1 of 
Chaetogaster must be recognised ; and I feel the more con- 
fidence in this conclusion, on finding that the species are 
identical with those recognised by the lamented Belgian 
naturalist. The Chaetogaster Mulleri of M. d’Udekem, which 
I have found in the river at Oxford, appears to be the Ch. 
niveus of Ehrenberg, under which name I have mentioned it 
in my former paper. M. d’Udekem expressly states that the 
sexual condition of Ch. Limncei was unknown to him. What 
he states with regard to the other two species, Ch. diaphanus 
and Ch. niveus {Mulleri), will be gathered from the figure 
(fig. 1) ; s. r. he calls seminal receptacles ; e. V., “ entonnoirs 
vibratiles,” i. e. ciliated efferent ducts ; h, two “ hard pieces” 
at the opening of the ducts ; ov., the ovary. The drawings, 
both in the case of Ch. diaphanus and Ch. Mulleri, are very 
sketchy, and do not give the relations of the organs men- 
tioned to other parts at all. The “ hard pieces” were not 
detected in Ch. diaphanus, but only in Ch. Mulleri, whilst in 
the former a clitellus is figured, and the ova are stated to 
have an orange-coloured vitellus, which distinguishes them 
readily from those of Ch. Mulleri. The ova are said to be 
formed at various points on the body-wall, and not from a 
specialised ovary. My observations on Chaetogaster Limncei 
do not agree with these, some differences being doubtless due 
to the difference of species. I find testes in the position, and 
somewhat of the form indicated in d’Udekem’s drawings as 
“ seminal receptacles.” I have completely failed to detect an 
“ entonnoir vibratile,” and cannot fix its position clearly 
from d’Udekem’s indications. I do not find the mesial mass 
of ova which d’Udekem calls ovary ; but on either side of 
1 There is also Schmarda’s South American C.filiformis. 
