226 Records of the Indian Museum. [Vou. VII, 
The condition is therefore to be compared with what occurs 
in Bourne’s Chaetobranchus, where there is no budding zone, and 
the process of division resembles rather a simple fission of the animal 
into two. It is to be contrasted in this respect with the species I 
found at Lahore, where a regular budding zone is formed, 
as in Nats, Chaetogaster, etc. Further, the present form agrees 
with Bourne’s in the fact that asexual reproduction is apparently 
a comparatively rare occurrence; Bourne, out of a large number, 
found only a few specimens dividing; whereas in many species 
of Naididae it seems to be rather the exception than the rule to 
find an animal which is not preparing to divide. 
It would appear from the specimen undergoing division 
(pl. xi, fig. 4),—1f I am right in supposing that a separation of the 
two individuals was here not far off,—that a considerable amount 
of the development of the head has still to be gone through after 
fission is completed. This is confirmed by the actual condition 
of two of the free-living specimens examined (the fourth and sixth; 
cf. ant., under the description of the prebranchial region). 
Can this inference be used to explain the remarkable 
variations in the distribution of the prebranchial setae ? In other 
words, can we suppose that all specimens which show fewer 
than four pairs of ventral setal bundles in front of the gills have 
recently been separated, and have not yet completed the develop- 
ment of the anterior end,—ana that the production of the full 
number of setal bundles will follow intime ? Would the specimens 
described above have developed, in all cases, four bundles of ventral 
setae in the prebranchial region if they had been left alive ? 
This seems quite possible with regard to such specimens as 
the fourth and sixth of the foregoing description ; here the other 
structures of the anterior end—prostomium etc.—were also 
incomplete, and it is quite possible that the setae might, later, 
have developed along with these. 
It does not seem very probable with regard to some of the 
other specimens. For example, in that represented in pl. x1, fig. 3, 
the seventh of the previous description, the prostomium, mouth, 
and other features of the anterior end are well developed, yet the 
ventral setae are wanting ; had they been going to develop, there 
would have been at least some signs of them. The same may 
be said with regard to the fifth. And in the specimen with three 
well-developed setal bundles in the prebranchial region (pl. x1, fig. 2) 
there would probably have been some sign of a fourth if a fourth 
had ever been going to develop. Again, asexual reproduction 
apparently here, as in Bourne’s worm, does not occur with any 
great frequency ; hence the chances are very much against six out 
of these seven specimens having been very recently separated, 
as the above explanation would demand. . 
The matter may therefore be summed up as follows: —In 
the present form the process of asexual reproduction is accom- 
panied by the formation of only the rudiment of a budding zone ; 
separation of the two resulting individuals takes place early ; 
