44.6 FRANK E. BEDDARD. 
The occasional presence of two pairs of receptacula ovorum in 
certain species of Pericheta may be regarded as a “ set off.” 
(1) The double dorsal- vessel is found in six out of the twenty 
known species of the genus; but it also occurs in Deino- 
drilus, in Microcheta, and in Megascolex ceruleus; 
it is therefore characteristic of at least the two former genera. 
I am not inclined to regard this character as one of great 
importance from a classificatory point of view, since two forms 
so nearly allied as Acanthodrilus dissimilis and A. nove- 
zealandie differ in this very particular, and, moreover, do 
not always differ (I have not found a double dorsal vessel in 
all examples of A. nove-zealandiz). The retention of the 
double dorsal vessel is certainly an embryonic character, com- 
parable to the partial persistence of the left aortic arch in 
many birds of quite different groups (Raptoressome Stru- 
thiones). If it were confined to one group it might be 
regarded as an important classificatory character in birds and 
worms. 
II. Further Observations upon the Reproductive Organs of Eu- 
drilus, with special reference to the continuity between the 
Ovaries and their Ducts. 
The investigations of Perrier (33), Horst (26), and myself 
(2), have shown that the reproductive organs of Eudrilus 
present certain remarkable differences from those of all other 
Earthworms, excepting the genus Teleudrilus recently de- 
scribed by Rosa (388). 
In the male generative system the testes and sperm- 
sacs appear to be quite normal, that is to say, they differ 
in no important particular from those of other genera of 
Karthworms. The efferent ducts and the copulatory apparatus 
are, however, in many respects peculiar to the genus, being 
only paralleled in Teleudrilus. 
In the first place, the two vasa deferentia of each side are 
