in front of the first pair of abdominal fasciculi] in each of the 
zooids represented by a head (the first and fourth "roup as given 
above), I saw a pair of rounded masses placed one on each 
side of the nerve-cord, which were obviously developing ova, 
and anterior to these were undeniable testes. I afterwards 
found specimens in which there were still more fasciculi, fol- 
lowing in unbroken order a head and cephalic bristles, and at 
last obtained the worm drawn in fig. 2, which must be 
regarded as the sexual form of Choetoyaster Limncei. No 
longer remarkable for the small number of its segments, but 
having, in addition to its anterior region, sixteen or seven- 
teen segments, indicated by as many pairs of fasciculi, this 
form exhibits, somewhat strangely and instructively, the 
antagonism between Individuation and Genesis. Whilst the 
rapid process of fissiparous reproduction is going on, the 
individual zooid can only be said to consist of a head and 
four segments, of which the fourth is continually budding in 
both anterior and posterior direction, separating from its 
parent by the growth of a new head ; but as the sexual com- 
pletion of the individual commences, the rapidity of the 
process of fissiparous reproduction is stopped ; and the new 
segments, as they grow, instead of becoming separated from 
the parent-stock by the intermediate, development of heads, 
remain attached as parts of the whole until the Chsetogaster, 
once remarkable for its paucity of segments, becomes a 
lengthy worm (about the one third of an inch long) of a head 
and sixteen or more somites. It may seem, at first sight, wrong 
to regard the development of sexual organs as belonging to 
individuation rather than genesis ; but it is when contrasted 
with the period of rapid asexual reproduction that we recognise 
the development of the sexual condition as-implying increased 
individuation. The nutrition of the growing segments neces- 
sary for them to develop heads and separate from their parent 
is diverted to the commencing genitalia, and, consequently, 
genesis is stopped, whilst individuation gains, but only tem- 
porarily ; for by the further development of those genitalia 
the worm will be so far taxed as to be destroyed, and death 
will put an end to the individuation altogether. 
The change in the number of segments which remain 
attached to form an individual is not the only change which 
occurs in the Chsetogaster during the development of the 
reproductive organs. The number of the bristles in each 
bundle is nearly doubled. Whereas, in the asexual zooids 
seen at other times of the year the cephalic fasciculi contain 
twelve, and the abdominal eight bristles apiece, I have 
counted in the sexual form between twenty and thirty bristles 
