Hl2 GEOLOGICAL SURVEY OF THE TERRITORIES. 
preceding segments in old specimens are more prolonged than in young 
ones. With the furea is the last abdominal segment usually a little - 
longer than the double length of the penultimate segment, however 
sometimes also a little shorter, which probably depends upon the age 
as well as upon the surroundings. I have yet to add that the longer 
the abdominal furea in the form Artemia is, the shorter appears the last 
abdominal segment; it is as if the furca develops on account of this 
secment, especially on account of the second half behind the sensory 
bristles (which are nearly in the middle of its length). This answers the 
circumstance, that in the species Branchipus, with usually great length 
of the abdominal appendages, the last abdominal segment is consider- 
ably shortened, as the abdominal segment, which corresponds to that 
part of the last abdominal segment in Artemia, which part is behind the 
last sensory bristles, 7. e., behind that part where Artemia lacks the ar- 
ticulation, which exists in Branchipus (excepting Branchipus stagnalis ?). 
Regarding the circumstance that the last apodous abdominal segment 
of Artemia is homologous with the two last, ¢. ¢., the 8th and 9th apodous 
segments of Branchipus, we must firstly realize the disposition of the 
sensory bristles on the abdomen of the species Artemia and Branchipus, 
and secondly the origin of the articulation in the middle of the last pro- 
longed segment of Artemia, immediately behind the sensory bristles, in 
the domestication of the entire generations of these animals in continually 
diluted salt water. On each apodeus abdominal segment of the Branchi- 
pide: the sensory bristles are at the end of the segment before the artic- 
ulation; the last segment makes an exception, which has no sensory 
bristles before the abdominal appendages. The Artemic show an 
equal disposition of sensory bristles on the postabdomen, with the sole 
exception that such bristles are also on the last (eighth apodous) prolonged 
segment, about in the middle or above it. As into the sensory bristles, 
located about in the middle of the !ast prolonged (eighth apodous) seg- 
ment in Artemia, enter likewise nerve-branches, as is the case with 
those at the end of the preceding segments, and the sensory bristles 
at the end of the segment in Branchipus (therefore also into those at the 
end of the penultimate segment), it follows that the first half of the last 
segment (eighth apodous) in Artemia corresponds with the whole penuliimate 
(eighth apodus) segment of Branchipus, while the second halt of this 
segment (eighth apodous) in Artemia is homologous with the last (ninth 
apodous) segment in Branchipus. As I do not ‘rite a monograph of a 
species, and. as for me only the disposition of the sensory bristles was 
of importance, I cannot give the number of bristles on each apodous 
abdominal segment. Sometimes I found only two bristles on the seg- 
ments, sometimes four, circularly distributed around the segment). I 
only know that these sensory bristles also exist at the end of the two 
first apodous segments opposite the external sexual organs, and also at 
the end of the last limb-bearing segment, likewise also on the other 
segments of this body-part. Spangenberg found in Branchipus stagnalis* 
sensory bristles by twos on the abdominal segments, and only on the 
eighteenth, being the seventh apodous segment, he found four ‘pristles. 
It is without doubt, thatin Branchipus stagnalis, in case it has only eight 
apodous segments, ‘the sensory bristles are not at the end of the eighth 
epodous segment, but before the faint articulation of this segment, 
which is figured by Claus, or if Branchipus stagnalis should, like the 
other species possess nine segments on the end of the eighth ‘segment. 
1 Zeitschr. f. wiss. Zool., vol. xxv, supplem. p. 28. 
2Loe. cit., Plate V, fig. 16. 
