64 
Proceedings of the Koyal Society of Edinburgh. [Sess. 
following segments the numbers of annuli diminish rapidly to two — the 
number present in each of the last twelve to twenty segments. The 
specimen shown in fig. 1 is rather contracted, and some of the grooves in 
this, and in other specimens examined, may be due merely to folding of 
the body- wall, brought about by contraction of its musculature. In other 
specimens, killed more fully extended, the annuli are fewer, and nearly 
all the branchial segments are clearly bi-annulate, the larger anterior ring 
bearing the chrntae and the smaller posterior one the gills (fig. 4). This 
condition was evidently exhibited also by Langerhans’ specimens (see his 
fig. 21 g), and it seems to be sufficiently constant to be considered one of the 
diagnostic features of this worm. 
The gills of Branchiomaldane vincenti are of a very simple type, 
being composed of one, two, or three, rarely four, finger-shaped outgrowths 
of the body-wall, each of which contains an extension of the coelom and a 
vascular loop connected with the afferent and efferent branchial vessels. 
In the preserved condition the gill-filaments, which are not more than T5 
mm. long in the writer’s specimens, generally have an annulate appearance, 
due to the contraction of their muscles. In those gills in which two or 
more filaments are present, the latter arise either close together on the 
body- wall or from a short common base. 
The first branchiate segment is about the twentieth, but the position of 
the first gill is subject to variation : for instance, in one of the specimens 
examined the first gill is borne on the eighteenth segment, in two on the 
nineteenth, in one on the twentieth, and in two on the twenty-first segment.* 
In most specimens a few — two to six — of the anterior and posterior gills are 
simple, each consisting of a single filament, but each of the other gills is 
composed of two or three (rarely four) filaments. The last one or two 
segments may be abranchiate (fig. 4). 
The giils begin to arise about the time the worm attains thirty segments, 
and then develop rapidly ; for in a specimen with thirty-six segments, gills 
are present on the nineteenth to thirty-fourth inclusive. 
The colour of B. vincenti is usually pinkish, due to the blood-vessels 
being seen through the semi-transparent and feebly pigmented -j* body- wall. 
The epidermis contains abundant mucous cells, which secrete the envelop- 
* Langerhans records examples in which the first gill was borne on the twenty- third 
and twenty-fourth segments respectively. 
+ Specimens of adult B. vincenti and of young Arenicola about the same size differ 
markedly in the amount of their pigmentation. The epidermis of the former usually contains 
only a few dark granules which are situated chiefly at the anterior end of the worm, but in 
young examples of Arenicola a considerable amount of yellow or green pigment has already 
been formed. 
