14 MR. J. LUBBOCK ON THE DEVELOPMENT OF 
Tenth State (Pl. XVIII. fig. 10). 
In the ninth stage the insect adds about pth of an inch to its length; as, however, 
they are not all of equal size when they enter it, so also at the next moult they vary 
from 35 ths to ths. 
A specimen ;83;ths in length had antennze z%oths in length. They consisted of twenty- 
nine segments; but the penultimate has almost disappeared; and the apical would, I 
think, certainly be considered as a mere seta by any one who saw it in its present con- 
dition for the first time. 
The posterior angles of the mesothorax are more produced: in the last stage the two 
posterior thoracic segments were similar, but already the difference between them is well 
marked. 
The central tail is 42;ths in length, and is composed of about twenty-four segments. 
The fringe commences on about the ninth segment, and in some of the segments nearer 
to the apex it consists of four hairs on each side. 
The circles are most conspicuous round the third, fifth, seventh, eleventh, and fifteenth 
segments. Thus there are now two groups, each consisting of four segments. 
On the lateral tails the fringe extends to the thirty-first segment. The apices most 
strongly marked are the second, third, fifth, seventh, eleventh, and fifteenth. Comparing 
this with the same organ in the preceding state, it appears that the four segments which 
were then the eighth to the eleventh are now the twelfth to the fifteenth; that, on 
the other hand, the sixth and seventh have each divided, and, thus forming the quadruple 
group from the eighth to the eleventh, have added two segments to the whole organ ; the 
other two new ones having originated in the division of the first and third. In some 
specimens the apices of the seventh, eleventh, and fifteenth, with the whole of the four 
following segments, are slightly darkened, a character which is much more strongly 
marked in some specimens than in others. Some, indeed, have scarcely a trace of it. 
The larger branchiz are now about 5;$5ths in length, and near the middle are almost 
as broad. Figs. 22, 23, & 24 give an idea of the distribution of the air-vessels in them ; 
the details, however, vary a good deal, even in the two branchis forming a single 
pair, the most usual differences being in the magnitude of the branches a and b, which 
are often so large that the main trunk appears to divide into four subequal divisions. 
The main trunks, as well as the two great longitudinal vessels in the body, are surrounded 
by a variable deposit of brownish pigment. 
Near the base are scattered a few markings, consisting of double circles, which, in 
subsequent stages, become much more numerous. They resemble those which occur in 
the skin of the body. 
The little lobe already mentioned has become quite distinct. Tt is more or less reni- 
form, and as yet only 525ths in length. The first and last pairs of branchize, however, 
which have throughout been less advanced than the middle ones, are still single. 
A specimen which I isolated on the 8th of September, while it was in the third state, 
and the account of whose subsequent development, confirmed and checked by comparison 
with others, has been given above, arrived at the tenth stage on the 27th of September, 
being then $ñ ths in length. 
