384 GEOLOGICAL SURVEY OF THE TERRITORIES. 
spindle-shaped ganglion-cells before terminating in the spherical gan- 
glion-cells at the insertion of the three seta. The same general ar- 
rangement of the nerve-fibers and cells is seen in the same organs earlier 
in life at fig. 3. 
In Chirocephalus holmani, according to Dr. Gissler’s figure, the first an- 
tennee each bear not only three terminal setz, but also a series of about 
five sense-sete like ateu-pin (Fig.8). These are apparently homologous 
with the olfactory cylinders of Ley dig* on the smaller antenna of Asel- 
lus aquaticus. 
The second antenne.—These are not apparently organs of any special 
sense. In the Limnadiade they are evidently derived from the “ruder- 
arme ” of the Cladocera, being large, long, biramous appendages of con- 
stant use as oars in swimining, the long setz assisting in the oar-like 
movements. The form is very persistent i in this family, the use of the 
appendages being the same in each genus. 
In the Branchipodida, the second antennez of the males are modified 
in a striking way, which afford apparently good specific characters useful 
in such a difficult genus as Streptocephalus. As clasping organs their 
use is Seen in the engraving of Artemia (fig. 17 in text). The rounded 
sinus between their bases just fit over so as to inclose the back of 
the female, and the two knob-like processes further seem to hold her 
fast; in Branchinecta the structure of the base of the claspers is the 
same, while the simple unarmed second joint is not particularly well fitted 
for prehension: In Branchipus each second joint has a stout spine 
pointing inward which acts as a prehensile apparatus, as has Streptoce- 
phalus, in which also the second joint is variously divided into prehensile 
parts. 
In Chirocephalus and Thamnocephalus the second joint is incurved, 
and thus rendered sufficiently prehensile. 
It appears, then, that the highly specialized. male second antennz 
have lost perhaps altogether their sensory functions, or their use as 
swimming organs, like those of the Limnadiade, and are simply of use 
as clasping organs and minister solely to the reproductive function. 
In the Apodide, as stated by Lankester (Quart. Jour. Micr. Se., April - 
1881, p. 346), the existence of the second pair of antenne has recently 
been denied. ‘“Zaddach states that they were generally absent in A. 
caneriformis, but were found by him in two cases; Huxley states that 
he was unable to find them in Apus glacialis examined by him, whilst 
Claus, whose statements have the very greatest weight, both on account 
of his extended investigation of the morphology of the Crustacea and of 
his special observations on the development of Apus and Branchipus, 
brings forward the total absence of the second pair of preeoral append- 
ages in Apus, as a special characteristic of the family Apuside.” Gers- 
taecker simply, in reference to this point, quotes Zaddach’s statement. 
Lankester adds “In the adult Apus cancriformis and Apus dukii, from 
Affghanistan (?.A. himalayanus), this second pair of praoral append- 
ages, although reduced to a rudimentary condition, is always present, 
*Leydig, F. Ueber Geruchs- und Gehérorgan der Krebse und Insecten. Reichert u. 
du Bois-Raymond’s Archiv. 1860, Tab. 7, fig. 4. 
Spangenberg (on Limnadia her mannt, "Zeits. fiir W. Zoologie Suppl. 1878) thus de- 
scribes the taste-organs. On the 1st antenne “they are situated—usually six In nDum- 
ber—as small, clear points on the hinder much-swollen surface of the base of the an- 
tenne, and may be traced back, as all these taste-filaments, to the spines on the nau- 
plius-antenne. Thestructures on the base of the known pale taste-cylinder, described 
by Claus as ‘highly characteristic shaped nerve-pins,’ are the young taste-cylinders 
reaching out in “the succeeding moult, and are not of a nervous nature, but cuticular 
early growths. 2 
ene ear 
Peaster 
