482 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
in locomotion. The young animal (after the first day) is nearly as 
rapid in its movements as the adult with its twelve pairs of legs, but 
moves somewhat less often. 
The pair of cerci, which are evident at the posterior end of the young 
Scutigerella, is sufficient evidence that the addition of segments must 
be between the last leg-bearing segment and the last segment of the 
body as Wood-Mason (’83) has already shown. 
The body of the immature Scutigerella is provided with long setae 
or bristles. One bristle usually arises from each side of the body 
about midway between the coxae of successive legs. At the posterior 
end of the body there is a pair of especially long setae which are 
.sensory in an especial sense. This sense organ, the anal stylet, has 
been called by Muhr “Tastorgan.” If the cerci be considered homol¬ 
ogous to the walking legs (Wood-Mason), then these organs are 
homologous either to the bristles between the successive walking 
legs previously spoken of or else to the parapodia to be described later. 
The whole body of the animal is also covered over with shorter hairs. 
These are especially developed on the joints of the antennae and the 
mouthparts. 
The ventral drawing (pi. 36, fig. 3) shows two series of the most 
interesting organs to be found on the animal, the parapodia and the 
ventral sacs. All indications are that the view of Schmidt (’95) is the 
correct one and that the so called “ Pseudobeinen,” “Huftgriffeln,” 
“Exopoditen” or parapods are really rudimentary legs. Scutigerella 
is hatched with at least four pairs of parapods and more probably 
with five pairs. The first two pairs of walking legs seem to have 
neither parapods nor ventral sacs though ventral sacs may be present 
in a greatly reduced form at the base of the coxae of the second pair of 
legs. Both these organs appear by the coxae of the third pair of legs 
and also with the fourth, fifth, and sixth pairs. The ventral sacs 
which are to be near the seventh pair of legs in the adult, are not visible 
in any of these recently hatched larvae. The small legs, however, 
can be seen in some cases, under favorable conditions of light, at the 
base of the seventh pair of legs. 
The ventral sacs or “blood gills”are eversible organs and one can 
cither assume that the fifth pair has been drawn in in all of these speci¬ 
mens or that they are not yet functional and will appear at a later 
ccdvsis. 
%! 
Williams ( 06) stated that Scutigerella larvae were hatched with six 
pairs of legs and not seven as has just been shown. These larvae 
