E. B. Wilson—The early stages of Renilla. 449 
In fig. 6,the rudiment of a new zooid, h, has appeared on 
the upper side of the primary one. In fig. 7 this is fully 
developed and two lateral zooids, a, a, have appeared. 
The group may now be compared with the entire colony as 
shown in fig. 2. In both there is a larger primary zooid 
with a pair of lateral zooids and a central zooid on the upper 
side. Moreover, it is important to observe that, in both, the 
lower (or smaller) chamber is turned away from the center of 
the group. In other words, the zooids are not only grouped 
in the same manner but their axes have the same relation to 
each other. 
In the next typical stage, fig. 8, four new zooids, ¢, ¢, d, d, 
have appeared in the angles between the four preéxisting 
zooids, and in these, also, the small chamber is turned away 
from the center of the group. 
Very soon after this stage, many of the individual zooids be- 
come themselves centers of multiplication and according to the 
same law as before. A study of figure 9 (which represents an 
. almost fully developed group) will show this. Thus p is the 
primary zooid, A the central or upper zooid (which might be 
compared to the “ Hauptzooid ” in respect to its relation to the 
group) and a, a the primary lateral pair which are still undi- 
vided. 
As in fig. 8, d and d aresimple; but cand c have themselves 
become secondary centers of multiplication. On one side, ¢ has 
become a group of four (exactly like the entire group in fig. 
7); and on the other side the corresponding zooid is repre- 
sented by a group of two. Besides these, two incomplete 
way. 
4. The peculiar central zooid of the colony is not the pri- 
mary polyp but a secondary zooid; the term “ Hauptzooid ” is 
therefore a misnomer. 
5. The posterior (i. e. aboral) part of the body of the primary 
polyp persists as the peduncle of the colony. 
