SPONTANEOUS FISSION IN AN AQUATIC WORM. 277 
young forms may be found attached to the adult. The process 
goes on until the JVazs has been reduced to twelve or fourteen 
rings ; then a pause occurs, and the animal increases in length to 
forty or fifty rings, when a new cycle commences by division in the 
middle of the body. Reproduction of lost parts readily takes place 
in this group.” 
These are quotations from two of our greatest authorities on the 
Annelida, so that their variance is remarkable. 
Mr. A. Hammond, F.L.S., the president of the Postal Micros- 
copical Society, in an article in the Journal of the Society for 1882, 
calls attention to the views of Dr. Williams, and describes an act 
of fission in a Naid worm, Stylaria paludosa, as witnessed by him- 
self and Mr. Baily. I may remark that the Stylaria paludosa of 
Lamarck is the same species as JVais proboscidea of Linnzeus. 
Oersted places it in his second division of Naids, which includes 
those that have “‘segmenta quatnox anteriora (interdum sola duo) 
S FSS 
Sees 
mem Fre 
Fig. 67. 
setis superioribus destituta.” Mr. Hammond describes a constric- 
tion taking place amidst some new segments which had been 
formed towards the lower third of the body, and below the con- 
striction a new proboscis and eye-spots, the separation of the worm 
into two parts, and the formation of a new head on the tail half. 
He does not, however, tell us whether the worm was mature or 
immature, whether there were any ova in the perivisceral space, 
whether a tail was formed on the head half, how long the two 
individuals lived, and whether either of them took food after sepa- 
ration. Nor shall I be able to enlighten you upon some of these 
points ; but as far as my observation goes I will record it. 
One day last summer I found a specimen of St¢y/aria, three- 
eighths of an inch in length, with the bristles absent from some of 
the segments of the lower half of the body. Upon examining it 
with the compound microscope, I found the constriction and new 
proboscis described by Mr. Hammond. 
