40 W. C. Minor upon Fission in some Annelids. 
the parental ring, as a fixed point, there is a continuous ring-form- 
ation and elongation backward; and that anteriorly to it there is 
a limited elongation of the general body, also by ring-formation 
from before backwards. There is, then, unlimited growth back- 
ward from the fixed point, and a limited or defined growth back- 
ward toward the fixed point from the place of fission. The pa- 
rental included ring, the most anterior of the series, is here the 
fixed point. In “budding”—“knospenbildung”—the most ante- 
rior ring of the series also, though a wholly new-formed one, be- 
comes the fixed point, from which, by continuous ring-formation, 
the Naid elongates backward, and toward which a limited series 
of ring-formations proceed from the point of fission.? The resem- 
blance between the two is perfect; and as the fixed point is not 
related to specializations of the alimentary tube, as I at first sup- 
posed, and is in Stylaria proboscidea, where it occurs by “parting,” 
four hook-combs back of the mouth, as it is in Nas and Dero, 
where it occurs by budding, while in S. longiseta it is six hook- 
combs back, the genetic relations of the two processes, in these 
genera at least, are completely one. But, as I have already said, 
though the distinction appears unessential in the genera I have 
examined, the terms are convenient and as merely descriptive 
terms are used here. 
The “commencement of fission” was observed in a large pro- 
portion of the buds given off from the individuals of Stylaria 
and Nais which were under observation, and the result is given 
in the following table. 
Stylaria—between 12-183 combs in none. MNais—between 17-18 combs in 3 
13-14 “ 2 18-19 ae 
14-15 ae 19-20 “ 4 
15-16 - 9 20-21 o oe 
16-17 " 1 21-22 whe 
the commencement of fission and continued fission, notwith- 
7 There is an interesting analogy between this process in the Naids and the em- 
bryonic growth of Torebella, as p afd by Milne Edwards. He has remarked, 
Obs, sur le dével: t des Annélides, Ann. des Sci. Nat., 1845, 3me Série, T. iil, 
that the first d part is not the cephalic, nor the anal, but the esophageal, and 
that growth takes place both anterior and posterior to this by succession from 
before backward. Other speculations and analogies suggest themselves here, but 
are in our present know wholly premature. ; 
