SPONTANEOUS FISSON IN AN AQUATIC WORM. 273 
mouth and body cavity, passing it at the same time through the 
suctorial disc. Then withdrawing the point out of the cardboard, 
I carefully pressed the head downwards with a blunt instrument. 
It then turned upon itself, and when I withdrew the needle it was 
really inside out. 
Professors Huxley and Martin state there is reason to believe 
that the Hydra reproduces itself by self-division. I have discovered 
this to be a fact, by seeing the Hydra self-divide on several occa- 
sions. The process was as follows :—Attaching itself to the sides 
of the glass, it extended its body and tentacles to an extraordinary 
length, and then seizing a water plant with its tentacles, it began 
to contract at both the anterior and posterior ends, whereby the 
centre was drawn out to a very delicate thread, when by a long 
pull, a strong pull, and a pull all together, the separation was 
effected. In due time the head acquired a new foot, and the 
other part a new head. Natural division only takes place during 
the warm weather. It thus appears to me that in dividing Hydra 
we simply imitate nature. 
SPONTANEOUS: FISSION 
iN Aon AO Ana CW Ou i: 
By W. Biackpurn, F.R.M.S. 
Read before the Manchester Microscopical Society on 6th September. 
HE order Oligocheta comprises those worms that move partly 
by means of stiff bristles projecting from the soft integument. 
These bristles are placed in rows on the lateral and ventral aspects 
of the body, the dorsal surface being free from them. ‘There are 
no tentacles or branchial processes. Within the integument are 
two layers of muscles, an external circular, and an internal longi- 
tudinal layer. These structures enclose a cavity, called the ferzves- 
ceral space, which is filled with a corpusculated fluid. Floating in 
this fluid is the alimentary canal, which carries on its upper surface 
the dorsal vessel, containing a reddish non-corpusculated fluid, 
which it propels forward towards the head. ‘This coloured fluid 
then passes through a plexus of small vessels, which again unite to 
form the ventral vessel, through which the fluid passes backwards 
towards the tail. The ventral vessel is attached to the lower sur- 
face of the alimentary canal. Another plexus of small vessels 
completes the circuit, and restores the fluid to the dorsal vessel. 
Besides these plexuses, which are cutaneous, a number of large 
