1903.] IN THE ‘ CHALLENGER’ COLLECTION. 53 
specimens, on 22 of the species in question, 15 of which were 
established by Bate himself. Furthermore, he refers Petalidiwm 
Bate, Sciacaris Bate, Acetes H. M.-Edw., and Lucifer Vaugh. 
Thomps. to his family Sergestide ; of Lucifer he describes two 
species, but the genus must be more thoroughly studied than has 
hitherto been done before the examination of the ‘Challenger’ 
specimens ; Sciacaris Bate has one species, which is only a larva of 
a Sergestes, and the type seemed to be wanting in the Museum ; 
of Acetes, Bate had no specimens; and Petalidium is mentioned 
below. 
Of Bate’s 31 species of Sergestes only 6 are really mature forms, 
25 being larvee. Special attention has been paid to the adult speci- 
mens preserved in the Museum and enumerated by Bate; on two 
of these specimens I have established two new species, and 
besides I add notes and some drawings to the representations of 
Bate. Unfortunately nearly all the specimens of rare and 
especially interesting species were very much mutilated. 
Our present knowledge of the adult species of Sergestes of the 
Atlantic fauna is far from complete, but yet we are acquainted 
with so many species that it was possible for me in my earlier 
paper either to refer the J/astigopus-forms examined to the 
mature species, or to describe the older larval stages and some- 
times the black-eyed but still immature forms, so that they can be 
recognized with certainty and referred to the mature forms when 
these are discovered in the future. All the Atlantic larval forms 
from the ‘Challenger’ seen by me have now been referred in a 
similar way. But many larve established by Bate as valid species 
of adult or sub-adult animals have been secured in the Pacific. 
Our knowledge of the mature stage of the species living in that 
vast ocean is still rudimentary; and I have therefore not been 
able to refer the larvee of three of Bate’s species to any species 
established on adult specimens.  Bate’s types of his species 
established on larval forms are often either defective or very 
young, wherefore I thought it of little use to describe and figure 
them again; but I have generally added some notes on their 
affinities, and sometimes also a few corrections to his descrip- 
tions. When the Pacific has been moderately well explored 
by further expeditions, many adult forms and their larval stages 
will be discovered ; and a future student of the group will then be 
able to refer at least some of the larvee, which I cannot interpret, 
to their adult forms. To the young larve described by Bate as 
species of JJastigopus I pay no attention at all: the types seem 
to be lost. 
I think it convenient first to deal with all the ‘ Challenger’ 
species in the same consecutive order in which they are described 
in Bate’s Report ; then to put together some results of the investi- 
gation; finally, to mention more fully the luminous organs in 
Sergestes challengeri, n. sp 
In order to abridge the descriptions, in the following pages— 
as in my earlier paper~-I make use of some abbreviations :— 
