212 
Calliohdella lo2)Mi 
quickly into the bursa. In the forward-going part of each ductus 
ej aculatorius the epithelial cells are large and in general very indistinct, 
and their nuclei observable also only with difficulty. The epithelium 
is surrounded by a very powerful circular muscle layer. The cells here 
commence by degrees to become secreting cells, and in the backwardly 
directed part of the ductus ej aculatorius they become more and more 
obviously such, and at the same time more indistinct. 
The bursa is a very characteristic feature of Calliohdella. This is 
a saccular organ into which the common end part of the ductus ejacula- 
torii opens, and which opens outwards by means of the male genital 
aperture on the second clitellar segment, through which it is able to 
be everted, and is distinguishable from that of other genera by its 
enormous and peculiar development. It is a flattened sac whose wall 
is considerably plaited, an especially large fold going forward immedi¬ 
ately in front of the openings of the ductus ejaculatorii.. The inside 
of the bursa is lined with epithelium consisting of high narrow cells. 
The musculature is extremely powerful; partly because the wall of the 
bursa is covered with large muscle threads crossing each other, which 
form duplicated layers, partly because there go out from the muscle 
layer both to the dorsal and ventral sides, giant muscle fibres often 
having a diameter of 40-50 p,, and containing nuclei up to 25 p, in 
diameter, which size is important in comparison with other leeches. 
These muscles send out branches with which they root themselves fast 
both among the muscles of the wall of the bursa as well as the walls 
of the body. The wall of the bursa towards the dorsal side immediately 
behind the opening of the ductus ej aculatorius is developed in a peculiar 
manner so as to form a spherical organ *3 mm. in thickness, which is 
a process of the cavity of the bursa flattened and conical in form 
directed dorsally and forwards. The bursal epithelium is here small 
celled, under it is a thin layer of loose connective tissue, afterwards a 
very firm connective tissue membrane, in which are fastened muscles 
which stretch towards the periphery of the organ, where they fasten 
themselves to a similar membrane. Outside around this again lies 
a layer of loose connective tissue which contains fine muscle threads. 
For most of these histological details I am indebted to Johannson. 
The whole bursa, except a little region in the neighbourhood of its 
opening, is surrounded by a portion of the body cavity which even extends 
forwards round the ductus ejaculatorii. With the help of the above- 
mentioned muscles the whole bursa can be everted and forms a penis 
capable of standing out at right angles to the body, which plainly must 
